'자전거 이야기/Fitting'에 해당되는 글 8건</h3>

  1. 2010.07.23 Aerodynamics and Cycling - http://home.hia.no/~stephens/aero.htm
  2. 2010.07.23 The Aerodynamics of hand height - http://www.slowtwitch.com/Tech/The_Aerodynamics_of_hand_height_131.html
  3. 2010.07.23 Aerodynamics, what a drag - http://beatyourpb.ning.com/profiles/blogs/aerodynamics-what-a-drag
  4. 2010.07.11 Technical Q&A with Lennard Zinn: A question of crank length - http://velonews.competitor.com/2003/11/bikes-tech/technical-qa-with-lennard-zinn-a-question-of-crank-length_5257
  5. 2010.07.09 What science says of seat angles - http://www.slowtwitch.com/mainheadings/techctr/seatangle.html
  6. 2010.07.09 move forward or back? - http://www.tri-ecoach.com/art7.htm
  7. 2010.07.08 BUYER'S GUIDE: SELECT THE PROPER FRAME FOR YOU - http://www2.bsn.com/cycling/articles/framesize.html
  8. 2010.06.23 Proper Bike Fit for Triathletes - http://www.slowtwitch.com/mainheadings/techctr/bikefit.html

Aerodynamics and Cycling - http://home.hia.no/~stephens/aero.htm

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Aerodynamics and Cycling






This article comes from Jim Martin Ph.D, an engineer, associate professor in exercise science at the University of Utah, and a friend of mine from my doctoral student days. Jim has been a Masters Champion on the track, and has coached the EDS cycling team. He also has spent about as much time as anyone doing Wind tunnel testing for cycling, both at the GM and Texas A&M wind tunnels. This article was written for triathletes, but the information still applies to the straight cyclist.
It is very popular to use the term ‘aero’ to describe bicycles, wheels, helmets, and handlebars. However, do we really know exactly what ‘aero’ means, and what the consequences of aerodynamics are to you, hich we measured drag in the wind tunnel of seven riders, then had them ride at three steady state velocities while we measured power with an SRM crank and wind conditions with an anamometer. The results indicate that our predicted power matched our measured power with a standard error of 5 watts, and demonstrate that this is a valid model for power during real world cycling.

Knowing the power required for a given riding velocity may be meaningless if you don’t know how much power you can produce. If you, as a Triathlete or Duathlete, are equally well trained at cycling and running, and have average running economy (1.6 kcal/kg/mile) and average cycling efficiency (19% gross cycling efficiency) your sustainable power output can be estimated from this simple equation: Power (watts) = 60 * Body weight (lb.) /10k run time (minutes). Based on this equation, Table 1 presents the estimated power output for 4 categories of triathletes/duathletes. Keep in mind that if you are estimating you power in a multi-sport event, you should use your ‘multi-sport run’ time, whereas if you are estimating your cycling time trial performance, use your ‘run only’ time. These estimated power outputs will be used to illustrate the effects of aerodynamics on a variety of riders.

TABLE 1. Estimated cycling power output for a 70 kg person based on 10k multi-sport running time

Elite Well Trained Trained Recreational
10k Time 35 min 40 min 48 min 60 min
POWER 264 watts 231 watts 192 watts 154 watts

Although much attention is focused on the aerodynamics of equipment, the most important aerodynamic consideration for a bike and rider combination is the rider. A typical 70 kg rider on a regular bike with standard wheels will have a drag of about 8 lb., a better position will reduce drag to about 7 lb., and an excellent position will yield a drag of 6 lb.. Based on these drag numbers, and the power outputs estimated above, equation 1 can be used to predict the effects of these positions on cycling performance on a flat course with no wind shown in Tables 2 and 2a. The differences in performance with no change on power are remarkable, ranging to about 6 minutes when changing from a typical to an excellent position.


TABLE 2: Predicted 40k time, flat course, calm conditions, 3 body positions, standard wheels.

Position Drag @30mph Elite WellTrained Trained Recreational
Typical 8.0 62:49 65:51 70:16 76:01
Good 7.0 60:14 63:07 67:22 72:57
Excellent 6.0 57:23 60:10 64:07 69:47

TABLE 2a: Predicted time savings for a 40k based on 2 body positions compared with a typical position, flat course, calm conditions, standard wheels.
Position Drag @30mph Elite WellTrained Trained Recreational
Typical 8.0 62:49 65:51 70:16 76:01
Good 7.0 2:35 2:44 2:54 3:04
Excellent 6.0 5:26 5:41 6:09 6:14

The key elements of a good aero position are:

1. Horizontal torso. Defined by having your chest, or better yet, your back parallel to the ground, this is absolutely the most important element, as it can result in large magnitude changes in aerodynamic drag. Unfortunately, it may be the most difficult to achieve, because as you approach this position, your thighs start to hit your torso. This interference imposes limits on your body's aerodynamic position, but is due to traditional bike geometry (i.e.; seat tube angles of 73 to 75 degrees). The way to overcome this limitation is to go to a more forward position, which will allow you to roll your whole body forward. Note of caution: a forward position seat post and long steeply-dropped stem may allow you to assume a good aero position, but will result in a bike that is not well balanced, and my be dangerous to ride. A much better approach is to buy a frame that is designed to be ridden in a forward position. These positions are uncomfortable in two ways. First and foremost, by rotating your hips forward to get your torso horizontal, you are rotating your weight right on to your soft and tender parts. Specifically, riding in this position may exacerbate the condition of prostatitis that is common among cyclists. Extra seat padding helps but does not eliminate the problem. A truly anatomical saddle that distributes your body weight over the whole seat might really help. Some riders try to alleviate this problem by tilting the nose of the saddle down, but this only results in a tendency to slide off the saddle and to strain your shoulder and arm muscles. Secondly, and to a much lesser degree, you tend to get a sore neck the first few times you ride, the discomfort lessens with time and can be minimized with stretching and massage. These draw backs are minimal because you don't have to ride the forward position daily to go fast on it. My experience with Team EDS, as well as my own bike is that you only need to ride it once a week (maybe less) to stay adapted to the position.

2. Narrowly spaced elbow pads. Narrow elbows are an essential detail of an aero position. However, the magnitude of improvement is much less than what is achieved by adopting a horizontal torso position. Research conducted by Boone Lennon has shown that subtle changes in elbow width and aero bar angle may have significant effects on drag. This research was performed on traditional geometry bikes, with the torso adopting the characteristic cupped shape, and probably illustrates the need to block air flow out of the torso area. More recent data on riders in a horizontal torso position shows much less effect from these variables. I do not believe these two findings are contradictory, rather, they indicate that once the torso is horizontal there is little you can do to improve or impair aerodynamic drag.

3. Knee Width can change aerodynamic drag by up to half a pound. Pedaling with your knees close to the top tube is an essential part of good aerodynamics.


Is there a trade-off between position and power output? If done badly, maybe, but if done well, no. Recently, Heil et al., (MSSE, May 1995) have investigated this question, and the results tend to show that your cardiovascular stress for a given power is increased by decreasing the trunk to femur angle. Therefore, if you lower your elbow position, you may need to move the saddle forward to maintain your trunk to femur angle while getting a lower, more nearly horizontal torso position.

The effects of aerodynamic wheels can be substantial. They can lower the aerodynamic drag by about 0.4 lb. compared with standard wheels with round-wire spokes and require about half the power to rotate. For the following examples, I will use a Specialized 3 spoke front and a lenticular rear disc. Tables 3 and 3a show the predicted effects these wheel will have on 40k time trial performance.

Position Drag @30mph Elite WellTrained Trained Recreational
Typical 7.6 61:40 64:38 68:54 74:39
Good 6.6 58:58 61:47 65:55 71:23
Excellent 5.6 55:57 58:39 62:35 67:47

TABLE 3a: Predicted time saved in a 40k by using aero wheels compared to standard wheels, flat course, calm conditions, 3 body positions.
Position Drag @30mph Elite WellTrained Trained Recreational
Typical 7.6 1:09 1:13 1:22 1:22
Good 6.6 1:16 1:20 1:27 1:34
Excellent 5.6 1:26 1:31 1:32 2:00

The difference made by aero wheels is about a one to two minutes. When I was preparing this talk and I got to this part, I didn’t believe the model’s prediction. So I recruited a friend and went out to a fairly flat loop and rode at constant power with regular and aero wheels. The results were almost exactly what the model predicts. This study needs to be repeated with better control such as wind and road grade measurement, but it provides anecdotal evidence that the predicted effects of wheels are realistic.

Similarly, the effects of aerodynamic frames can be substantial. The best frames can reduce drag an additional 0.3 lb. compared with round frame tubes. The critical areas of a frame seem to be the leading edge (fork, head tube, handlebars) and the area between the rider's legs. The frames that perform the best tend to have air-foil shaped leading edges and seat tubes (or no seat tubes). The effects of an aero frame are estimated in Table 3.
TABLE 4: Predicted 40k time, flat course, calm conditions, 3 body positions, aero wheels, aero frame.

Position Drag @30mph Elite WellTrained Trained Recreational
Typical 7.3 60:53 63:47 68:04 73:40
Good 6:3 58:05 60:51 64:55 70:21
Excellent 5.3 54:59 57:39 61:30 66:38

TABLE 4a: Predicted time saved in a 40k by using an aero frame compared to a standard frame, flat course, calm conditions, 3 body positions.
Position Drag @30mph Elite WellTrained Trained Recreational
Typical 7.3 0:47 0:51 0:50 0:59
Good 6:3 0:53 0:56 1:00 1:02
Excellent 5.3 0:58 1:00 1:05 1:09

As you can see above, the effects of an aero frame result in saving about an additional minute.
The effects of light weight components seem to be a topic of interest for many triathletes/duathletes, however the effects of weight on cycling performance may not be as significant as one expects. To illustrate the effects of weight I have modeled a very tough out and back 40k with a constant grade of 3% which results in 600m or about 1970 feet of climbing/descending with aerodynamic bikes that weigh 22 lb. and 17 lb., and a slightly less aero bike/position that weighs 17 lb. The results are shown in tables 5 and 5a.
TABLE 5: Predicted 40k time, 3% grade out and back course, calm conditions, 2 body positions, aero wheels, 3 bikes.
Bike Wt. Drag @30mph Elite WellTrained Trained Recreational
22 lb 6.3 65:04 69:38 76:55 87:24
17 lb 6:3 64:37 69:05 76:12 86:27
17 6.8 65:52 79:22 77:31 87:47

TABLE 5a: Predicted changes in 40k time due to weight and aerodynamics, 3% grade out and back course (600m or ~1970ft of climbing/descending), calm conditions, 2 body positions, aero wheels, 3 bikes.
Elite WellTrained Trained Recreational
Time saved w/5lb lighter bike -0:27 -0:33 -0:43 -0:57
Time lost with 0.5 lb more drag, 17 lb bike +0:48 +0:44 +0:36 +0:23
0.5 lb More drag, 23 lb bike +1:15 +1:17 +1:19 +1:20

An extremely light bike on a very tough climbing course will only save you about 30 seconds to 1:00, but if this lighter bike compromises your aerodynamics even a little bit, you will be SLOWER by 23 to 48 seconds. Interestingly, lighter wieght is more of a help to slower riders. Increasing drag by 0.5 lb. slows you down by about 1:15 on the same weight bike. IX. Till now, I’ve modeled everything in calm conditions, however, I personally have rarely ridden in calm conditions. Wind effects can be remarkable, largely because you spend a longer time in the head wind than you do in the tailwind, and consequently, the slower head wind portion has a greater effect on average velocity. Table 6 demonstrates the effects of 5 and 10 mph winds on an out and back course, direct head wind one way, tail wind the other.
TABLE 6: Predicted 40k time, flat out and back course, windy conditions, good body position, aero wheels, aero frame.
Wind Drag @30mph Elite WellTrained Trained Recreational
Calm 6.3 58:05 60:51 64:55 70:21
5 mph 6:3 58:45 61:39 65:52 71:31
10 mph 6.3 60:48 63:58 68:40 75:02

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The Aerodynamics of hand height - http://www.slowtwitch.com/Tech/The_Aerodynamics_of_hand_height_131.html

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The Aerodynamics of hand height

Written by: John Cobb
Date: Mon Nov 26 2007

A couple of years ago I was doing a new bar study and took some pretty well staged photos to write an article about bars. I never got around to the article but I stumbled onto the data again and I’ve decided to write it.


There is no agenda – as aerobar makers like myself sometimes have – attached to this inquiry. It’s just more info to help you explore and define your own best rider position.


The results of the runs are given as an average of the aero drag through a range of 0 – 5 – 10 – 15 degrees or yaw, or crosswind. The results from each yaw angle are given a different value or percentage of the total. Most riders see very little time at “0” head wind, they see a lot at 5 and 10 degrees yaw and not to much at 15 degrees. The amount of time you feel a wind at the larger angles is a factor of how fast you go — the slower you are the apparent crosswind you have [Editor’s note: Hed has a Yaw Calculator on its website to help demonstrate this].


I also tested at a corrected 30mph, we do this to get more stable drag numbers. Most wind tunnels are built to test much larger objects with drag forces in the hundreds of pounds. A typical bicycle with rider only has drag force of about 7 pounds on average. The Texas A&M tunnel where I did this test, will repeatedly measure down to 4 grams difference, it’s very accurate for cycling. People always say, ”I can’t go that fast” and while that might be true, the end results at a more realistic 20 – 24 mph turn out exactly the same.


So I purposely used a very basic bike, I used a standard steel round tube frame with standard 32 hole box rim wheels. Using some aero frame would have been okay but I really wanted to just study hand and bar positions and see how the air reacted. Testing with large aero section wheels will always mask small changes because of the airflow hysteresis* as you run the yaw sweeps during the testing. I also tested some basic things like, if you have the zipper open on your jersey, or you use a CamelBak under the jersey, fun things to know. [Editor’s note: What John means by “airflow hysteresis” is the tendency for the air to “remember” the shape of its flow around an object as a bike is angled via a turret in the tunnel. Deep section wheels and frame tubes enhance this tendency, and may overshadow the changes in drag caused by altering hand positions.]
The base set up started with the rider on the bar tops, recreational riding style. I used a rider who was at the tunnel doing work on his TT position and equipment, he’s about 5’11” and 155lbs. Our base position starting point was an average drag of 10.38 lbs. or 4715 grams of drag. This means that every square inch of exposed surface is “feeling” a pressure of 10.38 lbs. While this particular rider is easily capable of producing very high watts, I have used a number to figure the time differences of 200 watts average. Our base line time for a 40k, or roughly 25mile event would be 1:17:45 @19.17 mph. The game in cycling aerodynamics is to then see how you can make that pressure be less on the rider. Because humans are not very good engines, it takes many long hours and a lot of miles to increase the power of the rider through training. Decreasing the drag is easier than building rider power.
The next test was having the rider on the brake hoods in typical racing form. We had the jersey zipper open all the way for this. This resulted in a drag of 9.176 lbs or 4165 grams. This gave a 40k time of 1:14:55 @19.9mp Next we closed the zipper. This dropped the drag to 8.804lbs or 3997 grams, or 1:13:59 @20.16mph (so, close up those zippers).


That’s quite a difference and it helps show the effect of airflow across the chest area. As we move along, working with airflow around the chest and stomach will really drop the drag numbers. Just to gain more data, we had the rider go to his drops. At triathlons we see this a lot -- riders have aerobars but they ride on the drops. This usually is a result of lack of comfort or bad positioning. This resulted in a drag force of 7.852 lbs. or 3564 grams, for an anticpated 40k time of 1:11:29 @20.86mph. This is an improvement over the brake hoods but there is still a lot of room for improvement.


Next I moved on to aerobar setup. I used a standard adjustable clip on bar on the original road bars. This was not an equipment test, only general positioning guidelines. Not to stray off course here, but I will go into a small discussion about bar positioning and effects. The individual riders shoulder shape, chest shape and back shape all effect the final best position for each rider. This is great to know and if you have access to a wind tunnel, you can work out every last detail for an individual rider, most people don’t have a wind tunnel available or the desire to spend the large amount of money involved. While doing a rider positioning, you need to visually look for problems, wide knees generally aren’t good, loose clothing is terrible, very high shoulder heights are not good and hands lower than the elbow pads generally are a bad thing. I have also found that helmet choice will not effect position choice, get the position right for best aero and power and then get the right helmet.
For our aero bar testing we used the same seat angle and saddle position. This rider had good flexibility and pelvic rotation, I wanted to compare apples to apples on equipment so I did not rotate him more forward for just the aero bar test. Our first set of runs were with the elbows set wide -- approximately thigh width -- then I changed the bars from a high position, to a mid position to a flat position. This picture is of the bars at medium height, wide elbows. The results of the three bar height runs were:

Bars high
Drag = 7.055lbs (3203 grams)
40k in 1:09:13 @21.35mph.

Bars med
Drag 7.227lbs. (3281grams)
40k in 1:09:43 @21.39

Bars flat
Drag = 7.106lbs. (3228grams)
40k in 1:09:22 @21.5mph.

Next I moved on to elbows in a narrow position, not extreme narrowness but as close as comfortable for normal age group racers.

Bars high
Drag = 7.068lbs. (3209grams)
40k in1:09:15 @21.53 mph.

Bars medium
Drag = 6.986 lbs. (3171grams)
40k in 1:09:01@21.6mph

Bars flat
Drag = 7.187 lbs. (3263 grams)
40k in 1:09:36 @21.43mph.
It is easy to see that using aero bars is a good thing, It also is easy to see that unless you are competing for every last second, there’s not a huge difference in the many variable bar, hand and elbow positions. I do a lot of rider positioning work that is not done in a controlled wind tunnel, and what I find is that rider comfort and the ability to stay in the aero bars is far more important. Also note that in this test elbow widths determined the best hand height positions.


The greater availability of power measuring equipment means a rider might dial in a position offering 10 or 15 percent more power by moving the location of the elbow pads or hand height. This additional power will almost always more than offset any minor increase in drag.
As an example, if we take the worst of the aero bar setups in this test and plug in an additional 20 watts, the times will drop to a 40k of 1:07:10 versus 1:09:43.


At this time I’m not a very big fan of the “hands in your face” positions for triathletes. Yes, they can be fast, but for multisport racing I do not find them very comfortable. I also have found that when a rider rides upwards or beyond an 80-degree seat angle position, the high hands generally are not as good as lower hand positions. This applies to both power generation and drag. Road racers have to deal with rules limiting the seat to bottom bracket relationships, so hand height is something important for them to consider.


As usual, this testing only led to the need to do more testing, specifically with a forward geometry rider, possibly including two different shoulder shapes and the two basic back shapes. I’ll be working toward that.
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Aerodynamics, what a drag - http://beatyourpb.ning.com/profiles/blogs/aerodynamics-what-a-drag

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Aerodynamics, what a drag

For successful time trialling, finding an aerodynamic position is absolutely essential. If you train hard to improve your performance and then fail to exploit your aero opportunities, you are throwing away vital minutes. There is a common belief that unless you are riding at 25-30mph, aerodynamics are pointless, but research does not support this theory.

I ride slow, is all this relevant?
Enhancing aerodynamics will save you a ‘specific percentage’ and if you are slower, you are out there riding much longer so this percentage may work out in your favour! The various charts in this article show time savings with various aero components when riding at 100, 200 and 300 watts for a 25 miles TT, you will see that whilst riding at lower power outputs produce slower times overall, the time savings from aero equipment are potentially greater. Novices should take heart from this as should those riding longer distances of 50 miles, 100 miles, 12 or 24 hours. If you are riding long and slower, don’t presume that aero isn’t relevant, it definitely is.

Is size important?
One of the key performance indicators for cycling is the power to weight ratio, if you complete a maximal ‘ramp test’ and divide the highest power output by your body weight in kilograms, that’s your figure. There is a common presumption that power to weight ratio is only relevant for hilly courses, but that presumption in wrong. Bigger riders have a greater body surface area and the power to body surface area ratio is very important for time trial performance and research has shown that if you cut a big hole through the air you will go slower than smaller riders with similar power output (Jobson et al 2007).

It’s all about the legs
The legs definitely have a lot to do with it but it isn’t ‘all’ about the legs. The first thing you can do is to optimise your body position and make the smallest shape possible. There is an issue with getting yourself into an aero shape, it generally reduces power output, sitting upright creates a greater hip angle which is associated with more power, crouching low closes the hip angle thereby reducing power output.


Look at the cyclist picture above, the red line marks the hip angle. If the rider were to sit up the gap between the thigh and the abdomen would open and the hip angle would increase, this would help to increase power output but aerodynamics would worsen. There is a ‘trade off’ between power and aerodynamics, if you are riding into a headwind you may well go quicker by riding in a more aerodynamic position despite a slight drop in power, when you are climbing slowly it’s likely that you would benefit more from opening the hip angle and sitting upright.

Look at the figures below which list the drag area (cm2) for different riding positions, less drag is more beneficial:

Position

Hands

Arms

Drag area (cm2)

Seated

Tops

Straight

4,010

Seated

Brake Hoods

Bent

3,240

Seated

Drops

Bent

3,070

Seated

Aero Bars

Typical

2,914

Seated

Aero Bars

Optimised Position

2,680


*Data taken from ‘High Performance Cycling’ Human Kinetics Publishers, stats for 70kg cyclist.

Developing your fitness and your ride position are the first steps to going faster, always develop your aero position before buying a new bike, once you have found the optimal position for you, go to the bike shop and tell them the new bike must match your current set up perfectly!

I’ve got money to spend
Lucky you, the tables below show time savings for various components. Some of them are relatively cheap such as bolt on aero bars, whilst disc wheels and aero frames are relatively more expensive.

Wheel Type

40km @ 100 watts

40km @ 200 watts

40km @ 300 watts

Standard

87:50

67:43

58:29

Aero Wheels

86:37

66:46

57:39

Disc and Aero Front

86:20

66:32

57:26


Handlebars

40km @ 100 watts

40km @ 200 watts

40km @ 300 watts

Standard Handlebars and Clip on Bars

87:50

67:43

58:29

Integrated Aero Bars

86:40

66:48

57:40


Frame Type

40km @ 100 watts

40km @ 200 watts

40km @ 300 watts

Standard

87:50

67:43

58:29

Semi-Aero

86:52

66:57

57:49

Full Aero

85:14

65:39

56:40


Fork Type

40km @ 100 watts

40km @ 200 watts

40km @ 300 watts

Oval Legs

87:50

67:43

58:29

Airfoil Legs

87:10

67:11

58:01


*Data taken from ‘High Performance Cycling’ Human Kinetics Publishers, stats for 70kg cyclist.

You can see that time savings for wheels and frames are relatively similar with aero frames saving more time at higher wattages. The first step is definitely a set of bolt on aero bars if you enjoy riding your road frame (or don’t have a separate time trial bike) and next a set of aero wheels. Some riders have specific road and time trial bikes and if you are considering this option, there are some basic guidelines you need to take into account.

Helmet choice
Aero helmets may not look appealing in the car park but they have been shows to give up to 4% improvements in performance over a 25 miles time trial course. Some studies have shown that an aero helmet positioned effectively can give an extra 5.38 metres per watt, which equates to approximately a mile extra in one hour if you average 300 watts, possibly time to look odd and be proud?

Should I buy a time trial frame?
Your frame is a triangle made up of the top tube (runs from saddle to bars), the down tube (from bars to pedals) and the seat tube (from pedals to seat post). When you look at your bike from the side you will notice that the seat tube angles back slight so the saddle is behind the pedals. If the seat tube were more vertical (moving the saddle forwards) this would be a ‘steeper seat tube angle’.

Time trial frames have steeper seat tube angles and in some cases shorter top tubes to push your forwards, this is great when you are using aero/tri bars as they place you in the perfect position but it’s not great for ‘sit up Sunday riding’. Road bikes by comparison are great for ‘sit up Sunday riding’ but when you bolt on the aero bars in most cases you will be stretching a little too far.

Time trial bikes are great for riding fast in straight lines and that is what they are generally used for, they are not so great for cornering, descending and climbing due to the frame geometry. Think about the events you will be doing before spending a lot of money on a new bike which doesn’t do the job.

I have a road bike only but want to time trial
There are a couple of simple things you can do to turn your road bike into a time trial machine. We have already outlines above that generally you will reach too far if you add aero bars to a road bike so to reduce the reach either:

1. Buy mini aero bars (these are easy to find and go no further than the end of your brake hoods) and this reduces reach by bringing the front of the bike back towards you.

2. Buy a forwards angled seat post (this is a seat post with a forwards bend and replicates a steeper seat tube angle) and this reduces reach by pushing the saddle forwards.

Pushing the saddle forwards (forwards angled seat post) puts you in a powerful forwards position but isn’t great for your ‘sit up Sunday riding’ as outlined earlier. Buying short aero bars doesn’t affect your ‘sit up Sunday riding’ but the position isn’t as powerful (and potentially not as aero), as you are not as far forwards.

One simple solution is to have 2 seat posts with saddles permanently attached and the correct heights marked on the posts. When you ride a time trial or triathlon event put your tri bars on and your forwards angles seat post, after the event, take off the tri bars and put your normal seat post back in. It will take you 2 minutes to swap posts and saddles and cost you £100 for an extra post and saddle.


About the author of this training article
Marc Laithwaite, is Sports Science & Coaching Director, at The Endurance Coach. Mark has a Bsc (Hons) sports science and is working towards his Phd sports science. He is a member of the British Association of Sports and Exercise Scientists (BASES), a British Cycling Federation Blood Analyst, BTF Level 3 Coach & Coach Educator, UKA Level 3 Coach and ABCC Level 3 Coach.

The Endurance coach, provides sports science and coaching support services for endurance athletes. Their services include VO2 max testing, lactate profiling and metabolic assessment for endurance athletes of all standards in their own sports testing lab. The Endurance Coach also runs a range of training camps throughout the year and offers physiotherapy and rehabilitation services. For more information or if you are looking for world leading coaches to assist you, e-mail The Endurance Coach.

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Technical Q&A with Lennard Zinn: A question of crank length - http://velonews.competitor.com/2003/11/bikes-tech/technical-qa-with-lennard-zinn-a-question-of-crank-length_5257

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Technical Q&A with Lennard Zinn: A question of crank length

By Lennard Zinn

Dear Lennard;
What is your formula for measuring crank arm length? I have a 73cminseam with a size 39 foot. I have been on 170’s for two years and havebeen able to progress with all training except hills. I was becoming frustratedbecause I’m only 130 pounds and should be able to fly up them. I’ve trieddifferent styles of climbing, etc. My husband and I decided the lack ofa 25 was not the issue; I just could not get on top of the gears I wasusing. I read your column and we had a 165mm from my son’s bike and decidedto try.I feel I’m getting on top of the gear, a good feeling because I feelI have somewhere to start now. My legs and intercostals did cramp up duringthe hill training rides but that should subside as my legs become accustomedto the new circle. My question- what formula do you use and where did itoriginate? Does it include the foot measurement? Also, going from 170 to165 would increase saddle height 5 mm but this is too high (for me). Anythoughts on this?Thanks for your input!
EricaDear Erica;
Take a few minutes to check out this site: www.nettally.com/palmk/crankset.htmlI think the formula on this site (21.6 percent of inseam) is prettygood. I have been using 21 percent of inseam for the last three years,and it has been working great, but my experience is primarily on the longend with the tall customers I usually deal with as a frame builder. I hadto come up with custom cranks (see www.zinncycles.com/cranks.aspx)as well as higher bottom brackets in order to be able to apply the solutionsthis formula suggests to tall riders, however.Another interesting formula yielding similar results comes from fitguru Bill Boston (www.billbostoncycles.com).He suggests measuring your femur (thighbone) from the center of the hipjoint to the end of the bone in inches. This number will be your cranklength in centimeters. For instance, if you have a 20-inch femur, you wouldhave a 20cm (200mm) crank. He also has proportionality formulas on hissite based on femur length that give a very wide range of acceptable cranklengths.Andy Pruitt, director of the Boulder Center for Sports Medicine andfit expert of many superstars, has a few other things to add. “Crank lengthformulas using femoral length or leg length are fine,” he says. “But ifyour style is mashing, use longer cranks, and if you are a spinner, shortenthem a bit. Mountain bike cranks should be a bit longer for that momentto get you over a rock. Use 2.5mm or 5mm longer for purely time trial usage,and vice versa for the track.” Pruitt also warns that, although a MarshallUniversity study showed that all participants regardless of body size wentfaster over short distances with each increase in crank length, you canhurt yourself if you use cranks too long for your legs. In that case, hesays that the compressive and shear forces in the knee joints “go up exponentially,”due to the sharper knee bend. (Compressive forces in the knee are stagnant,felt behind the knee. Shear forces are the result of fore-aft sliding ofthe condyles – cartilage-covered rounded femur ends – as they are rotatingon the soft meniscus – cartilage pad – atop the knee platform.) So, donot stray on the long side much beyond this proportionality relationship.Cranks that are too short are not dangerous, however. You may forfeit somepower by not using your muscles as effectively, but you put less stresson your knees.Using your 730mm inseam, Kirby Palm’s method (X .216) gives you 158mm,while 0.21 gives 153mm. I think that what is particularly significant isthat you clearly recognize that crank length should be proportional toleg length. Foot size only comes into play if you have relatively smallor large feet for your leg length. With an exceptionally large foot, theeffective leg length and leverage is greater, so the crank should be abit longer, and vice versa. Seems to me that a size 39 foot with a 73cminseam is not out of the ordinary.The 165mm crank is 22.6 percent of your inseam, which is much betterthan the 23.3 percent that the 170s represented for you.And yes, your seat should go up by 5mm when going to 165mm from 170mm.So should your handlebar. I don’t understand why you say that it wouldbe “too high,” since the distance to the pedal is the same.A side note: Since I get so much mail on this subject, I will take thisopportunity to clarify a few things. I published some crank-length testsin VeloNews in 1995 and 1996. Some of you may remember them and will have noted that they certainly did not come out with the 0.21 or 0.216 factorI am espousing here. These tests were either inconclusive or seemed toindicate that all riders, regardless of size, put out more maximum powerwith super-long (220mm) cranks, and that all riders had lower heart ratesat low power outputs with super-short cranks (100 to 130mm). My experimentalmethod in these tests was lacking, and if you click on the Kirby Palm linkabove you can find that pointed out.I was simply not willing to stop there, since I knew from personal experiencethat increasing crank length for a tall rider like myself (6 foot 6 inches)made a difference. When racing in the late 1970s, when I went from 177.5mmto 180mm cranks, the improvement in my results was marked. When I was onthe national team in the early 1980s, Eddie Borysewicz, the coach at thetime, told me that I should be using even longer cranks yet for time trialsand hill climbs. Miguel Indurain also understood this and had the cloutto get longer cranks made for him, though. Good cranks longer than 180mmcranks were not available when I was racing, but the past three years Ihave used 202.3mm and greatly prefer them.Following up on my interest in the subject, I have conducted other cranktests in the last eight years that improve on those early efforts. However,in understanding what went wrong in those 1995 and 1996 tests, I developedhigher standards for what constitutes a publishable test, and my subsequenttests still have not met that standard and thus have not been in VeloNews.Too bad, because I have put a lot of time and effort into a number of them!It is one thing if you are a physiology researcher trained to do thesesorts of studies and who has funding to do it. It is not easy to do a testin which you eliminate all other variables besides crank length. It requireslots of time, planning, subjects and equipment. Hardly the type of thingthat is realistic to undertake with no budget in order to write one articlefor a cycling magazine where another article on a different subject isdue right on its heels.Anyway, I have conducted all of these recent tests on the road and primarilywith tall riders (6 foot 5 and over) because it was simpler and cheaperto use my personal stable of bikes than to always be switching cranks onother people’s bikes. By being willing to take my custom crank length recommendations,my tall custom frame customers have also graciously acted as test subjects.While having data showing tall people going faster and generating morepower with proportional-length cranks on my own personal bikes is great,testimonials from people may be even more valuable. And my customers alwaysrave about how much more comfortable, natural and powerful they feel onextra-long cranks proportional to their leg length. Tall mountain bikecustomers report being able to smoothly power over obstacles they couldnot have before. And the higher bottom bracket makes hitting the chainringson logs and the like almost impossible, yet the rider’s center of gravityis no higher (since the bottom foot is still the same height above theground due to the longer crank).All of this indicates clearly enough to me that crank length must beproportional to rider size in some way. Whether you decide it is proportionalto leg length, thigh length, overall height or something else is a minorpoint relative to that. The same goes for what you think the constant ofproportionality should be. It could be something different from 0.21 or0.216, but whatever it is, it will indicate for a lot of people that theyshould be using a vastly different length than they are. That is the partthat is very hard to accept for a lot of people.No matter our size, all of us are by and large all stuck on cranks ofthe same length. The 3 percent difference between a 170mm and a 175mm hardlyconstitutes a length choice, and the 180mm length available in only high-endcomponents still does not broaden the range much. Accepting that cranksshould be scaled up or down with rider size opens up a whole can of wormsthat an awful lot of riders and component companies would just as soonstayed closed.Obviously, economies of scale of producing cranks go out the windowif you have to supply a range from say, 140mm to 220mm. The same goes forbike frames; if a manufacturer increases the bottom bracket height withevery increase in frame size in order to accommodate crank arms proportionalto the size of the rider, its costs and complexity of frame jigs goes up.There are obvious practical reasons to stick with the status quo. Thosemay have to do with what is best for the rider’s pocketbook but not necessarilywhat is best for the rider’s performance and comfort. No other conclusionmakes sense to me. If you accept that muscles and joints work most effectivelywhen operating in a certain range of motion, then it only makes sense thatmuscles, bones and tendons work that way for everyone. Short riders shouldnot be required to force their muscles through a greater range of motionthan the person with an 80cm inseam riding a 172.5mm crank. And on theother end, 7-foot basketball players do not bend their legs any less whenthey jump than shorter players. So why should they use minimal knee bendand operate their muscles only through a tiny part of their range whenthey ride a bike?Whew! That was a long answer. Sorry.
Lennard

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What science says of seat angles - http://www.slowtwitch.com/mainheadings/techctr/seatangle.html

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What science says of seat angles
by Dan Empfield
June 20, 2002 (www.slowtwitch.com)

The popular triathlon-related magazines have carried articles on what seat angle you ought to use. But has this subject been addressed in the not-so-popular magazines, that is, the scientific journals? Our sport’s glossy pubs have done a good job of presenting to the layman the "science" on hydration and hyponatremia and related subjects. It’s not overstating it to say that hundreds of studies have been carried out in each of those categories, with corresponding articles published in peer-reviewed publications.

But what about bike position? If Triathlete or Inside Triathlon has reported on what’s been published in the scientific journals, I haven’t seen it. What they’ve written is like what I’ve written, which is that according to the author and the mouse in his pocket, this seat angle or that one is better.

I’m not a real scientist; I just play one on the internet. But there have been real studies performed by real scientists on the subject of seat angles, and I thought I’d write about some of them. All the tests I’ll write about below had subjects riding on a modified bicycle ergometer, that is, a stationary bike with the ability to offer a range of seat angles. Not in every case could I find what the protocol was for handlebar alterations that accompanied a change in seat angles. Take for example, "Cardiorespiratory responses to seat-tube angle variation during steady-state cycling," by Heil, et al, (Medicine and Science in Sports and Exercise, 1995). This study had cyclists riding a bicycle ergometer at four angles ranging from 69 degrees to 90 degrees. We don’t know with any precision how the handlebars were altered to negate the ill effects of a bad-fitting bike. Just the same, the study showed that only at the shallowest of angles (69 degrees) did the respiratory system of a cyclist come under more stress than at any of the steeper angles.

Two years later two studies came out. The first of these was published in the same journal as the study above, and was entitled, "Influence of different racing positions on metabolic cost in elite cyclists" (Gnehm, et al). It did not specifically test seat angles, but the study is important to note. Its authors mention going in that, "The spectacular improvements of the 1-h world record in cycling in the last four years have highlighted the importance of aerodynamics in modern bicycle racing." In the early-to-mid ‘90s the record had been significantly lowered by Moser, Boardman and Obree, each of which used more and more exotic bikes and bike positions. This study tested 14 elite male bike racers in three positions: upright with hands on the tops, crouched with hands on the road bars, and laid out on the aero bars.

Gnehm looked at metabolic changes while riders were in these three positions, and noted that riders in the aero position paid a penalty of about 9 watts versus the other two positions. It also noted that this is minor compared to Gnehm’s estimate of 100 watts an aero positions saves by virtue of a lower wind resistance. This was an oft-cited study by cyclists in newsgroups and forums in the late ‘90s, but I doubt its relevancy. First, I doubt that an aero position saves 100 watts. That’s a huge number, and I would guess that 20 - 40 watts might be more like it. Second, it appears that Gnehm did not change the seat angle for his subjects when he flattened their backs and lowered their drag. What Gnehm’s study seems to indicate is that even if you put a rider in a fairly uncomfortable aero position, the power output doesn’t markedly diminish.

The second of the ‘97 studies was published in the Journal of Sports Sciences (Price and Donne) and was called, "Effect of variation in seat tube angle and different seat heights on submaximal cycling performance in man." The article stated that, "At a seat tube angle of 80 degrees, mean VO2 was significantly lower and power efficiency significantly higher compared with an angle of 74 degrees." Likewise, 74 degrees offered more efficiency than 68 degrees.

This study is interesting because it tests not only three different seat angles (68, 74, and 80 degrees) but variable seat heights at each angle. As the quote above suggests, 80 degrees is the most efficient angle at which to ride. But there is of course more to the story. What were the handlebar configurations? What were the stem heights, the hip angles? We’ll get to that.

Interestingly, Price, et al, noted that differences in seat angle preferences were specific to classes of athletes: "...in contrast, triathletes’ bicycles have steeper angles of 78 - 82 degrees." The author also references the Heil article (noted above) and suggested that one reason why Heil found that 68 degrees was the only angle in which his subjects performed poorly was in Heil’s choice of subjects, "80% of whom," Price noted, "were triathletes who normally ride at a steep seat tube angle."

This particular study simply utilized a seat shifter, a nifty device once in relatively common usage by triathletes in the early '90s. It replaced the bicycle’s seat post, and with a lever on the handlebars you could change your seat angle on the fly. I’ve tracked down the study’s author and emailed him, asking him to verify that no changes were made to the handlebar set-ups as the seat angles were altered during his study. I’ve yet to receive a reply. I don’t, however, see any notation that any change in the bikes was effected other than a change in the seat angle provided by the seat shifter.

The results of this test are, to me, startling. These were road racers riding a road race bike, and they in general rode with considerable economy at 80 degrees versus their usual angle of 74 degrees. Oxygen consumption at the given rate of exertion was about 37 ml/kg/min at 80 degrees versus about 38.5 at 74 degrees (if you’re consuming more oxygen to do a given amount of work, you’re working harder, i.e., you’re less efficient).

Why did the authors achieve this result? "The mean shoe-pedal angle changes produced by altering the tube angle," opined the authors, "would result in a decreased effective force during the first half of the pedal stroke but an increased effective force during the second half. We speculate that increasing the tube angle improves effective force transfer during the second half of the pedal stroke."

The authors also noted that this series of tests only related to riding on the flat, and to submaximal power outputs, often atypical of race conditions. Just the same, it’s an interesting result and may bear on the next and, for us, most topical study.

The definitive article is now passing its second anniversary since its publication. The "Effects of bicycle frame ergonomics on triathlon 10-km running performance," by Ian Garside and Dominic Doran, appeared in the Journal of Sports Sciences in June 2000. As was the case with all the studies on this subject, the tests were performed in strict lab conditions, with gas analyzers and all that stuff. All subjects rode stationary ergometers.

Unlike Price et al above, Garside utilized triathletes, but: "All participants were naive to training and racing on bicycles with steep seat tube angles (>76-degrees); all participants used a 73-degree frame geometry as standard."

As opposed to most of the testing up to this point, Garside’s protocol called for the tests to be conducted, "as fast as possible under race-like conditions." The test called for triathletes to ride a 40km simulation on both a 73-degree set-up and then on an 81-degree set-up, each followed immediately by a fast-as-possible 10km run on a treadmill.

The authors noted the improved bike/run performance in the field, "based on anecdotal testimony from athletes purporting to have experienced improved performance." But, they noted that prior to this study, "No empirical evidence exists."

Frankly, the results were groundbreaking, for three reasons. First, these triathletes absolutely blew away their "duathlon" performances in the steeper configuration. The average time it took subjects to complete the 40km/10km "brick" was about 1:50 at 73 degrees of seat angle, and it was a full 5+ minutes faster at 81 degrees.

Second, as this test was performed in England, the triathletes there were (as previously noted) "naive" to steep seat angles, that is, they all normally rode shallow. Imagine their surprise at the result! (For a further explanation of the tendency of UK triathletes to ride shallow, consider our 2001 Kona Bike Survey on UK-based entries).

And finally, these tests only measured the physiological responses to the biomechanical change generated by a steeper seat angle. As this test was performed in a lab on stationary equipment, the aerodynamic benefit one derives from the ability to achieve a lower frontal profile with a steeper seat angle was not part of the equation.

Where in this 40km/10km exercise did the time savings occur? There were some time savings achieved during the bike leg. Average 40km times were 1:04:10 in the 73-degree configuration and 1:02:54 for the riders when at 81 degrees. But it was in the first half of the run that the big time savings occurred. It took riders 24:15 to complete the first 5km off the shallow set-up, and only 21:41 after riding the steep bike (and remember, these triathletes had never run off a steep set-up before).

The time savings continued during the second half of the run, but the gap narrowed. The subjects ran 22:01 and 21:14 in the second half of the 10km after riding in shallow and steep configurations respectively.

There is one curious element to these results which is not addressed in the study. It is odd to me that as a group there was such a marked tendency to negative-split the run. While this is not as pronounced in the steep test (21:41 to 21:14) it is severe in the shallow test (24:15 to 22:01). This one element gives me pause when considering the parallel between this test and what happens at triathlons I attend.

As the authors discuss the results they say, "Unexpectedly, the time to completion of the 40km cycle section was faster under the 81-degree 'steep' than the 73-degree 'shallow' condition." This underscores the tendency, I think, for the traditional view to hold sway in the UK, which is that if steep is faster, it’s only because it helps during the run. Obviously the authors were forced to rethink that position, especially as there is still the untested (by them) issue of wind resistance to consider.

The authors only guess at the causes for the enhanced ability to perform with the steeper seat angle, and posit about the,

"greater contribution of the hamstrings and gluteus muscles (Heil et al., 1995). Although muscle recruitment cannot be determined from the present results, alterations in muscle recruitment or activation patterns can have the effect of distributing muscular work over a greater muscle mass (increased contribution of the hamstring and gluteus muscles) that would theoretically reduced the work rate per individual muscle fiber (Coyle et al., 1988)."

Juxtapose that statement, in which the operative phrase is "distributing muscular work over a greater muscle mass," with what Price says in the study above: "We speculate that increasing the tube angle improves effective force transfer during the second half of the pedal stroke." It seems that both authors feel that steep seat angles might distribute work over a greater range of the pedal stroke and in so doing lessen the peak torque that must be applied if should that power application be concentrated over a shorter arc.

The scientists quoted above uttered statements that are not unlike what I wrote a couple of months ago in my Intro to training with power: "I’m convinced that the bane of the triathlete during the bike segment is the peak power one puts out, and not only in terms of too many watts now and then during the ride, but peak power inside the pedal stroke as well." The difference, of course, between what I wrote and what the scientists wrote above is that I was simply writing from the seat of my pants, while Price and Garside had actual data they themselves generated to back up their hypotheses.

The demonstration that steeper seat angles (and not for tri bikes, but for road race bikes) is better is not knew. Gonzalez, et al, (Journal of Biomechanics) demonstrated in 1989, in "Multivariable optimization of cycling biomechanics" that the optimal seat angle for his subjects averaged 76 degrees (as is the case with all of these studies, however, this relates to riding on the flats). But Gonzalez’ study also demonstrated that riding with a cadence of 115 bpm was optimal, and this corresponds only roughly to a real-world race situation.

Though these studies were all conducted inside four walls, and took place on the "flats" and were only sparsely conducted with race-specific exertions, evidence is piling up in favor of steeper seat angles. And that is especially true when one considers the post-cycling run in triathlon, at least up through the International Distance.


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move forward or back? - http://www.tri-ecoach.com/art7.htm

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move forward or back?

By Coach Steve

With so many tri-bike options available it can be a challenge to make an informed decision about which one to buy. There are steel, aluminum, and composite frames, traditional designs and beam bikes, shallow to steep seat tube angles, even effective seat tube angles for bikes that don't have a seat tube! Picking the right bike can be as tough as choosing an energy bar…or a coach! I'll try to help by explaining some of the variables in bike positioning, specifically how your seat positioning affects your comfort, efficiency, and most important, performance.

The seat tube angle of your bike's frame is a critical factor for positioning and performance. It's important because the angle determines your positioning relative to the bike's bottom bracket (the area that contains the bearings that your cranks rotate on). This positioning profoundly influences the dynamic of your muscle movement while pedaling. When you switch to a frame with a different seat tube angle, a change of only 3 degrees is analogous to completely changing your swim stroke or your run's stride; it will take time to adapt to, and can have either a positive, or a negative influence on your performance.

Production bike frames available offer a range from 73 degrees for a traditional 'road bike,' to 78 degrees for a full-blown 'tri-bike.' This range can make a difference in seat position of as much as 3 inches forward or back (depending on your leg length) relative to the bike's bottom bracket.

So what effect does your positioning in relation to the bike's bottom bracket have on your pedal stroke and power? Seat tube angles that are shallow (73 to 74 degrees) place you further behind the bottom bracket and favor quadriceps strength over hamstring strength. They benefit athletes who've spent significant time 'in the saddle' (bike racers) getting their bodies used to flexibility and power demands on their quads and lower back. The shallow seat tube angles also create a better position for climbing—power at lower cadences. Steep seat tube angles (75.5 to 78 degrees) put you further forward and benefit athletes who have well-developed hamstring muscles (runners). Hamstring muscles along with our gluteus (butt muscles) are the dominant muscles driving us forward when we run. When you watch an experienced cyclist at speed notice they often move forward at high effort/cadence on the flats. Because of that steep seat tubes are more appropriate for flat courses. The steeper seat tube angles also open up (increase) the angle between our torso and legs as we maintain our optimal aerodynamic position. We're able to rotate our hips forward making less of a bend through our lower backs, thus reducing the stress and fatigue to that area.

A steep seat tube angle (forward position) simulates the motion of running progressively more the further forward we place our seat. A forward position can ease the transition between bike and run, which is especially helpful in sprint distance events. But there's a downside to moving forward, a point of diminishing returns if you will...

The quadriceps is our strongest muscle, and it can store much energy in the form of glycogen (carbohydrate in storage form). Our quads apply force during the down stroke of the pedaling motion—working with gravity through our body weight. The hamstring muscle group has less power potential, and in addition must work against gravity while pulling back and up to generate power. Favoring hamstring powered pedaling tends to deplete and fatigue the same muscles during both the bike and run, so we may be able to get away with this in short events, but it will probably catch up with us to some degree during longer events.

Another consideration is variation of power requirements on different parts of a race course. While riding fast on flats, it's natural to slide forward on the saddle as we increase our momentum with greater leg speed (cadence). As we climb a hill or fight headwinds, our cadence slows and power becomes critical. This is when we need to slide back on the saddle to develop more torque. Riders with ultra-steep 78-degree seat tube angles often complain that they can't climb comfortably, especially when out-of-the-saddle. Clearly both "forward" and "traditional" shallow seat tube angles have merit and and every frame is a compromise.

I favor a seat tube angle of 75 to 76 degrees and feel it gives me a balance between top-end speed on the flats and power on climbs. In general this is the position used by bike racers for their time trial bikes, and triathlon is nothing but one long time trial unless you race junior or pro ITU draft legal races. Taller riders can move back one-half to one-degree and smaller riders should move forward proportionally. This seat tube angle adjustment accommodates body size and femur (thighbone) lengths. Most frame manufacturers do adjust seat angles for height on their stock frame sizes.

You may be saying to yourself, "I haven't seen many frames with 75-76 degree seat tubes," and you're correct. There are two ways to compensate for a seat tube angle that you feel isn't optimal. The first adjustment option is at the clamping area of your seat post to saddle rails. The clamp that holds the seat's rails allows a range of about one-and-a-half to two inches of forward or backward adjustment. The second option is a special post that's curved or 'bent.' Either of these options can effectively shift you to the position you want with a variety of seat tube angles. Of course moving your seat forward or back also affects the distance to your handlebars and aero bars, but discussing that would go beyond the scope of this article. Suffice to say, keep all of your bike's proportions (especially top tube length) in mind when purchasing a new frame or making changes to your current bike.

The majority of multisport athletes seem to be moving away from the radical forward positions of 5 to 10 years ago. I encourage experimentation in the off-season to determine what works best for you. In setting a new seat position keep this in mind: You will perform most efficiently with the positioning your body has adapted to over time. Changes force your body into a new adaptive 'learning curve' and will not be advantageous in the short-term unless your position was very inefficient prior to the change.


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BUYER'S GUIDE: SELECT THE PROPER FRAME FOR YOU - http://www2.bsn.com/cycling/articles/framesize.html

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BUYER'S GUIDE: SELECT THE PROPER FRAME FOR YOU

by Eric A. Koide
Reproduced from: Cycling Science Winter '95

If you're looking to buy a high performance racing bicycle, take your time, research all your options, and come to an informed decision. Don't run out and buy the latest high tech innovation just because it looks or sounds great. Make your final selection carefully. Most important, make sure your new bicycle matches your riding position, your body's comfort zone, and the types of training and racing you do. Your new bicycle should help you to ride more comfortably and efficiently than before so that you can train and race longer, harder, and faster. The following will help guide you in your search to find a racing bicycle that will give you maximal results.

FIVE STEPS TO SELECTING A NEW RACING BICYCLE

1. RESET YOUR POSITION ON YOUR OLD BIKE. FIND YOUR COMFORT ZONE.
Before you select your new bicycle you should take stock of your old bike and determine what you liked and did not like about it and what changes you require in your new bike. Most important, you should analyze and reset your riding position and establish the parameters of your "comfort zone." The comfort zone is the position in which you ride the most comfortably, efficiently, and pain-free. Knowing the frame angles and measures you require to put you in this position will dictate which frames are best suited to you.

As a matter of course you should spend several weeks each year, preferably during the off-season or preseason, analyzing and resetting your ride position. Your objective is to find the position where you feel the most relaxed and biomechanically stable. This is accomplished by adjusting your saddle height and setback, stem height and length, handlebar width and drop, and crankarm length. Triathletes will also want to check and readjust their aerobar length and angle and armrest position.

While making these adjustments try to find the position that is the most comfortable and efficient. Don't be concerned about your most powerful or most aero position at this time. A comfortable and efficient position will allow you to train longer and harder whereas a powerful or aero position may be difficult and fatiguing to maintain throughout a full season of training and may lead to chronic aches and pains that reduce your productive training time.

Resetting your bike position is a continuing process that takes several weeks or months to accomplish. Make minor adjustments, ride on it for a week or two, then perhaps make more adjustments. Make position corrections to alleviate any aches or pains your body has acquired and make sure your new position does not cause any new aches or pains. Additionally, try out your reset position in a variety of workouts: long rides, intervals, hills, sprints, cornering on a crit course. Continue to make incremental adjustments until you find the most comfortable, efficient, and pain-free position possible.

After you've completely reset your position take a look at what you've found. Where is your seat position? Back in a relaxed position, in a neutral position, or pushed forward in an aggressive position? Have you raised or lowered your saddle? Perhaps you need to look for a smaller or larger size bike? How about your handlebar extension and drop? Does your reset position require your new bike to have a longer or shorter top tube? Perhaps you have ended up with a position similar to where you started?

2. SET GEOMETRY PARAMETERS FOR NEW BIKE.
From your position reset you can begin to determine the proper seat angle, top tube length, and frame size combination you need in your new bike.

Figure 1
Seat Tube Angle Rider Position Recommended Uses
shallow (<73.0) relaxed roadrace, century, ultra
normal (73.0 - 74.0) neutral roadrace, criterium
steep (74.0 - 75.0) aggressive criterium, time trial, triathlon
extra steep (>75.0) aggressive-aero time trial, triathlon

Refer to Figure 1 and compare your reset seat angle to the recommended seat angle for the type of riding and racing you do. Road racers who do lots of century distance rides in their training tend to prefer relaxed seat angles whereas criterium racers usually prefer a more aggressive seat angle to accommodate their need for power and sprinting. Triathletes tend to prefer an even more aggressive seat angle to attain a more aero position.

Don't be surprised if your reset position does not correlate with the position recommended for your racing interest. It is common for riders to be most comfortable with a more relaxed seat angle even if they prefer to race in a more aggressive position. Knowing your most comfortable seat angle and the recommended seat angle will give you a range of possible seat angles to look for in your new frame.

Your optimum position for comfortable training may be slightly different than your most powerful position for racing and you may make small adjustments between these positions throughout the season. When shopping for a seat angle take this into account and buy a bicycle that is midway between your most comfortable and most powerful or aero positions. During early season endurance training, when you are doing lots of spinning and distance, you may set your seat in a setback comfortable position. Then, as the season progresses toward important races, you may gradually shift your seat into your race-aggressive position.

Crit riders and triathletes tend to sacrifice comfort to attain a more powerful or aero position during races, but may find it fatiguing to maintain this position during year-round endurance training. Remember that this is a tradeoff and that what races well may be difficult to train with over the long term. If you have chronic or nagging aches and pains or any doubts, opt for a comfortable position. You'll be able to ride longer and harder in the long run, remain free of injury and burnout, enjoy the sport more, and probably achieve greater overall success in the process.

3. DECIDE ON MATERIALS.
Once you have determined the geometry parameters for your new bike, you are ready to decide on the materials. Nowadays high performance racing bicycles constructed of steel and aluminum as well as more sophisticated materials such as carbon fiber and titanium are all widely available. Moreover, the aerospace-derived titanium and carbon fiber are not as astronomically priced as they once were. Additionally, a few companies are experimenting with so-called "exotic" materials which have the potential for quality performance at incredibly low weights. Consult Figure 2 to help you determine which material's properties best fit your riding and racing requirements.

Figure 2
Material Advantages Disadvantages
Steel most versatile metal, most tunable performance characteristics, strong, inexpensive, crash damage can often be repaired inexpensively heaviest weight
Titanium most durable, most damage resistant, strong, resilient, lightweight, extremely comfortable ride characteristics expensive
Carbon Fiber lightest, stiffest, most moldable material, strong, shock and vibration absorbent cracking and damage from crashes is generally irreparable
Aluminium lightweight, inexpensive prone to denting when crashed and weakening due to metal fatigue
Exotics lightweight, strong most expensive

Steel is the most versatile material and can be drawn, machined, shaped, and alloyed with other metals to accommodate a wide variety of strength and performance requirements. The result is an impressive array of strong, comfortable, excellent handling, and inexpensive frames built of steel alloys. The one drawback to steel is that it is much heavier than newer materials.

Titanium is perhaps the best all around material for racing bicycles. It is extremely strong, lightweight, and durable, far outperforming steel in dhese respects. Additionally, it has the unique property of flexion without deformation. This results in a remarkably smooth and comfortable ride as the titanium frame responds to bumps, vibration, and torque application, but remains incredibly strong providing superior power transfer. Titanium is also the most durable of all frame materials and is extremely resistant to denting and metal fatigue. Additionally, titanium is a very unreactive substance and will not rust or corrode. Titanium's primary disadvantage is that it remains quite expensive.

Carbon Fiber is the lightest of all frame materials. Since it can be layered and reinforced, it produces some of the stiffest and strongest frames available. Additionally, it can be molded and sculpted into aerodynamic forms without sacrificing strength, making it a top choice of triathletes. Carbon fiber's one disadvantage is that in the event of cracking or damage the frame is not repairable and must be replaced. Also, a poor quality carbon fiber frame may be brittle and lack the shock absorption of top quality carbon fiber frames.

Aluminum is a popular material because it is extremely lightweight, produces strong tubing and framesets, and yet is remarkably inexpensive. Aluminum's major disadvantage is that it lacks the durability or damage and fatigue resistance of either steel or titanium.

Exotics are the latest wave of new materials. Some of the more notable examples are: ceramic composites, aluminum metal matrices, boron-aluminum compounds, and beryllium-aluminum compounds. Chemically these materials are significantly different from one another but they all have a high strength to weight ratio. Whether due to rarity or complicated production technology, exotics tend to be extremely expensive.

4. CONSIDER SPECIAL PERFORMANCE DESIGNS.
After determining your geometry parameters and materials choices, consider any other special requirements such as aerodynamics, aero positioning, light weight, 650C wheels, or special designs.

5. SELECT PROPER FRAME SIZE.
When you have finally chosen the best bicycle for you, or at least narrowed your choices to a few models, you can select the specific frame size that fits you best.

Measure your inseam. In your socks and on a solid floor, stand against a wall with your feet shoulder-width apart and place a thick hard cover book under your crotch so that it contacts your pelvic bone like a bicycle seat. Mark the height of the book against the wall. Measure from this mark to the floor to get your inseam length. Multiply this measure by 0.64 and 0.65. This will give you two frame sizes to consider. Look at the frame geometry chart accompanying each bicycle listing. Between the two sizes, select the size that gives you the best fit according to the seat angle and top tube length you need. If neither size gives you the proper seat tube angle or top tube length you desire you should consider a different bicycle.

If both sizes give you the proper measurements, you should select the smaller size frame. Although a frame that is too small can cause some problems, a frame that is too large is worse. With a slightly small frame you can lengthen or raise the stem and seatpost to get the proper fit. With a frame that is too big, it just remains too big no matter what adjustments you make. If the top tube is too long, your front center and steering will remain too long and you will always be overreaching.

Whatever high performance racing frame you select, make sure it matches your training and racing requirements and gives you access to both your comfort zone and your power/aero position. Consider all your options carefully and make an informed decision. Then, get out there. Go ride.

Eric Koide Aerospeed Review Davis, CA

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Proper Bike Fit for Triathletes - http://www.slowtwitch.com/mainheadings/techctr/bikefit.html

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Proper Bike Fit for Triathletes
April.03 by Dan Empfield
(www.slowtwitch.com)

This series of articles is the first major overhaul of my writings on this subject in over a decade. I've embroidered around the edges and spruced up my grammar, but as I write this, in the shadow of the Second Gulf War, it must be acknowledged that most of what resides in this section has remained unchanged since shortly after the First Gulf War. I thought it worth a revamp.

Why now? Because every few weeks I host between seven and ten bike shop professionals and triathlon coaches and I teach them how to fit their customers to their bikes for use in triathlons. That's caused me to have to take a very hard look at what I do. While nothing has dramatically changed in my approach, the way I teach it has changed, and is changing. As a result, the way I present it to my readers can and ought to change as well.

THE BASICS OF BIKE FIT
WHICH GEOMETRY STYLE IS RIGHT FOR YOU?
WHY MUST SEAT ANGLES MATCH FRONT END CONFIGS?
CLEAT MOUNT
SADDLE HEIGHT
DETERMINING WHICH POSITION IS BEST
A NEW FORMULA FOR SLACKER-ANGLED ARMREST DROP?
HOW TRI-SPECIFIC GEOMETRIES MUST BE RIDDEN
HOW DO YOU CHOOSE A BIKE AND H'BARS?


THE BASICS OF BIKE FIT

The steps to achieving a good bike fit are few and easy. First, you must decide which style of geometry is for you. Against the backdrop of some immutable rules that apply to every position you choose, you're free to ride however you want. You can ride with a seat angle of 74 degrees or with 81 degrees. There is no necessarily perfect or special, or even tri-specific geometry to which you ought to aspire.

Each of the three riders represented at right are in a position that is appropriate for triathlon racing. One immutable rule is that the range of motion in which your thigh musculature operates ought to be biomechancially sound. We might roughly refer to a "hip angle" that is formed by using the bony protrusion of your hip (greater trochanter) as the apex, and with that angle's lines being: 1) one that run from the hip to the foot, and, 2) from the hip to the bony protrusion of the collarbone.

That hip-to-the-foot line is a little tough to nail down. Ought it to be from the hip to the bottom bracket? Or to the maleolus (bony protrusion of the ankle)? Or to the pedal axle? If so, where? At the bottom of the pedal stroke? With the crank in line with the seat angle (or relative seat angle)? If it's the hip angle you're measuring, why measure the angle in its most obtuse configuration? Why not at its most acute, when your foot is at the top of the pedal stroke?

All these are valid observations, but it doesn't much matter. If the proper bike fit is in fact proper, it doesn't matter where you measure, but each of these lines formed by the proximal point (hip) and the terminus at the line's distal point (ankle, BB, pedal axle, whatever) is going to change depending on which distal point you choose. I personally favor the pedal axle at the bottom of the pedal stroke, and my definition of "bottom" (for the purposes of measuring this angle) is not at 6 o'clock, but at the point where the axle is in line with the seat angle.

The preferred angle is 90-95 degrees, and while I don't like angles more acute than that, I don't mind a more obtuse angle, up to a point. I can in some cases live with 100 degrees. I have a problem living with an angle greater than that. As long as this is your hip angle, however, it doesn't matter to me whether you're riding at 71 degrees or 81 degrees of seat angle. Realize, however, that as you rock yourself back in the saddle you're rocking yourself up in front, that is, your back will not be as flat and you will probably be punching a larger hole in the wind as you propel yourself forward.

Why would one want to be less aerodynamic? Comfort, plain and simple. Rotating one's body complex forward means you're no longer sitting on that padded place God provided for you. You're now resting on the saddle in places God did not intend in his infinite wisdom for you to rest. Perhaps the Grand Design did not contemplate triathlons.

When one rocks all the way back—the Green Rider—this is a road race position, and a proper road bike fit is easy to achieve. By “road bike” I’m talking about the Trek Lance Armstrong rides on those days in France when the whole pack starts together. No aero bars on that bike.

If you’re a triathlete, however, you no doubt feel compelled to have triathlon bars on your bike. You shouldn't. Not necessarily, at least. There is nothing wrong with riding—even while racing in a triathlon—on a road race bike with road bars, STI or Ergopower shifting, and no aero bars whatsoever. In fact, if you're new to the sport, that's probably the best choice you could make, especially if you're brand new to STI-style shifting and clipless pedals, and if you've never before ridden with tri bars. All that is hard to learn in one fell swoop.

Besides, in another month, or two, or six, you can bring your bike into the shop and have aero bars retrofitted onto this bike. This is easy, it's just a pair of clip-ons, and it takes 5 minutes to add them. If you add full aero bars, however, you may find that that perfect road bike fit doesn’t work anymore now that you’ve laid your body down on the apparatus that essentially turns your bike into a front recumbent.

The keys to a good fit while on aero bars are few, and easy to grasp. There is now a second angle with which to be concerned, and as is the case with the hip angle above, this second angle is not an angle on a bike—but one formed by your body. Remember that line running from your hip to your shoulder? Now imagine a line from your shoulder to your elbow. This “shoulder angle” formed between your torso and upper arm also ought to be 90 degrees. Achieve this angle and you’ll be comfortable.

(A NOTE ON MEASURING ANGLES: Finding the proper point on your shoulder can make these angles tough to measure, and the points differ depending upon which angle I'm measuring. I find that when measuring the hip angle the line ought to pass from the greater trochanter through the shoulder, and through the collarbone which, while in the aero position, will be in front of the shoulder. But when you're figuring your shoulder angle, the line representing the upper arm ought to pass through the centerline of the arm midway from front to back. The intersection of these two lines represents the apex of the shoulder angle being measured.)

The problem with sticking full tri bars on your “perfectly fit” road race bike is that the bike is too long for these bars or, if you prefer, the clip-ons are too long for the bike. You’ll notice that your shoulder angle is greater than 90 degrees. You’re too stretched out. The solution? Don’t get full aero bars. Buy a shorter bar made just for a road bike position. There are several out there. Cinelli makes two, the Spinaci and the Corna. Profile Design makes a very popular model called the Jammer, and a souped-up version called the Jammer GT.

The good thing about these bars is that they’ll allow you to achieve that 90-degree shoulder angle without changing the fit and set-up on your road bike. The negative is that the armrests aren’t hitting you under your elbows, but under your forearms, almost under your wrists. That is not optimal for a lot of people.

Enter the “tri bike.” This is a bike built around the proposition that you’re starting with a full aero bar, and the geometry of the bike is built around the use of the bar. This bike has a very different geometry than a road race bike, but the “rules” mentioned above still hold. How is that so?

Imagine a picture of a hill climbing specialist riding seated up Mont Ventoux. Stick a straight pin in his bike’s bottom bracket, and rotate the picture forward. His rider position won’t change, if you’re considering the “body angles” spoken of above. If you’re very good with a pair of scissors, cut out just the rider, separating him from his bike. Now rotate him forward around the same axis, leaving his bike in place (as in the photo below-left). You’ll notice his trunk moves forward relative to the bike’s bottom bracket. His back gets flatter. He’s assuming an “aero position.” The only thing we need to do is to place an aero bar underneath his elbows. And this is what a tri bike is—steeper seat angle, lower front end, and a shorter chainstay so as to draw the rear wheel back under the rider’s weight, so that the bike handles appropriately.

How much should you rotate this rider forward? It’s up to you. You can ride with a 73-degree seat angle, typical of a road race bike, more or less. Or you can ride at 80 degrees, common in a full-blown tri bike offering a very aero position. Anywhere in between—anywhere along this continuum—is fine. The steeper your seat angle, the lower your bars can go, that is, the flatter your back can be.

Realize, however, that there are equipment and configurational changes that follow each move along the "continuum." As you move back in the saddle your aero bar armrests ought to be raised higher, and will be closer in elevation to the level of your saddle height. As you move more forward, your armrests can be lower, and your back flatter. If you decide to ride more in a conventional (rearward) road race position, with road bars and STI shifting, your aero bar's extensions will be shorter, and your armrests will "move up" your forearms toward your wrists. The more forward you are, the lower you will be, and at some point on the continuum (maybe at around 77 degrees of relative seat angle) you'll want to change from road bars to pursuit bars and bar-end shifting, and then your arms will rest on the armrests with the pads more under your elbow than your wrists, and your aero bar extensions will be closer to full length.

"Why can't I ride my road race bike in a road position AND have full aero bars AND ride with the armrests under my elbows?" you might ask. You can. But then you're likely to have a shoulder angle much greater than 90 degrees, and you'll be uncomfortable. In other words, you can't have it all, so you'll have to pick which features you want, and which you'll choose to live without.

WHICH GEOMETRY STYLE IS RIGHT FOR YOU?

In the beginning of my remarks I wrote, "You must decide which style of geometry is for you." How do you decide that? When a person comes to me for a bike fit, I ask a variety of questions, such as:

  • Do you have only one skinny-tired bike, or will you own both a road race bike and a tri-specific-geometry bike?
  • Are you intending to road race on this bike, or commute, or do centuries and group rides with road riders?
  • Do you intend to spend a lot of time in the aero position, or only be there very occasionally?
  • How important is speed to you? (This is not a rhetorical question, there are plenty of people for whom the finish time is not especially relevant).

I will also attempt to ascertain how athletic this person is, and how high the effort level is likely to be during the bike leg of the race. I'll consider the person's morphology—someone who is carrying a lot of extra weight is going to have that weight coming down on the saddle and whatever place on one's anatomy is in contact with the saddle.

Something must be understood about a full-blown aero position. It is most comfortably ridden while under a fair amount of power and effort. Riding an exceptionally easy (perhaps recovery) ride is less pleasing in the aero position than on a road race bike. The easy solution is to have two bikes, which I do. But not everybody does, or at least they don't while still new to the sport. But that does not lessen the realities of which position is best for which style of riding.

Having an an aggressive, aero position for riding to Starbucks for coffee is like commuting to work in the city using a Ferrari. Sports cars are nice, but a Caddy is perhaps better for stop-and-go traffic. How often, and for how long at a stretch, will you be riding with effort in the aero position? That answer to that question will determine where along the continuum from shallow to steep you ought to be.

For this reason, I usually recommend a road race bike as one's first entre into tri-bike ownership. This bike is easy to ride, and the position is accessible to just about anyone. It's a better bike on which to learn click-shifting, clipless pedals, and the beginnings of riding in the aero position. It's a better bike for corning and descending. It may end up being the only style of bike you'll ever own for triathlon. And if you do migrate to a tri-specific bike, you'll still use your road bike for group rides, recovery rides, early season riding, and so forth.

Having said that, there is one other option. Consider the "pink" rider at right. That might be what we could term a "multisport" position, and is just a bit of the way forward in the continuum. One could achieve that position by retrofitting a road bike with short aero bars and moving a few centimeters forward, or by having a slacker-than-usual tri-specific bike. For that person who is looking to spend not too much money and who wants a bike built just for the "multisport" position, however, this category of multisport bike is gaining in popularity, and the Cervelo One, at just under $1000, is probably the best of the current lot.


The one thing to remember is that shallower-angled road and "multisport" bikes are best ridden with road bars and road-style shifters and brake levers. Choose a handlebar set-up which is appropriate for that point along the aero continuum with which you’re comfortable. Will you be riding in a road race position, at 72 to 75 degrees of seat angle? Choose road race (drop) bars with STI-style shifting and clip-ons. Are you going to be on a steep seat angled rocket? Choose pursuit bars and bar-end shifting.

WHY MUST SEAT ANGLES MATCH FRONT END CONFIGS?

I'm not very patient with bicycle manufacturing companies. They ought to know how to build bikes correctly, and you'd think that if they were going to spend a million dollars or more on a line of bikes for triathletes, they'd take the time to get it right. Unfortunately, it's common to have no one in these companies who actually ride tri bikes; neither do these companies' product managers seek valuable information or guidance during the design the process. If anything, they ask their dealers what they want. This is often the blind leading the blind.

As a result of a process like this, in recent years you've had Cannondale making a tri-geometry bike outfitted with road bars and shorty clip-ons (a no-no) and Giant making a road geometry bike outfitted with pursuit bars, full clip-ons and bar-end shifting. In point of fact, both these companies made one frame, and outfitted their cheap model with road bars, STI and shorty clip-ons, and outfitted the expensive model with the full tri set up. The difference between these companies' approaches is that C'dale chose a steep seat angled tri geometry for the frame behind both these front ends, and Giant chose a road geometry frame.

In the case of C'dale, the proper bike was its expensive model. Since this frame was a full tri geometry frame (78-degrees of seat angle), it ought to ONLY have been outfitted with pursuit/full clip-on/bar-end shifting. It never should've put road bars and a shorty clip-on on this frame (which is what it did with its entry-level model). Thankfully, this sort of mis-spec is in Cannondale's past and it now makes its tri bikes with quite a bit of forethought.

Giant's situation is current, and its approach is the opposite. Its cheaper bike, the TCR Aero II, is a road bike outfitted with road race bars/STI shifting/shorty clip-on. That's a front end that matches the bike's geometry. It's a good bike. But its expensive bike is the TCR Aero I, and it's got a full tri front end. I don't agree with this sort of spec. Happily, it's more or less fixable. Outfit this bike with a forward seat post or an M2Racer Power Module and the bike becomes more usable.

Let's say you were sitting at the dinner table and you were served a hot dog, a baked potato, mustard and sour cream. Those of you who'd put mustard in the baked potato and dip your hot dog into the sour cream ought to put a pursuit bar on your road race bike. For the rest of you, the moral of the story is this: There is nothing wrong with shallow angles, steep angles, road bars with STI, or pursuit bars with bar-end shifting; just make sure you put a front-end on your bike that is compatible with the style of bike you're riding.

The simple way to view it is this: If you're going to ride a traditional geometry, ride the bars that traditionally go with it (road race bars). You contact the bike in three places—where the bike meets your hands, your butt, and your pedals. These three places must be properly spatially related to each other, and they must allow the body to form the two 90-degree angles mentioned in the sections above.

There is a reason that full tri bars don't make sense on a shallow-angled tri bike, and it is related to your shoulder angle. When you're on a properly-fit road bike, and you're riding in a road configuration—73 degrees of seat angle, road bars, STI, etc.—and when your hands are on the hoods, you have something close to that magic 90-degree angle (when you're low and really going hard, with your forearms parallel to the ground). When you put a full tri bar on your bike, the clip-on's extensions reach considerably further forward than the forward protrusion of the hoods. If you extend all the way, and your hands grab the extensions' ends, your shoulder angle is much greater than 90 degrees. You're too stretched out. In order to achieve that 90-degree angle, you'll have to have a shorter clip-on—either a very short size of a full clip-on, or a model of "shorty" clip-on with shorter extensions by design.

Of course you could also achieve that 90-degree shoulder angle by moving your saddle forward instead of by moving the clip-on extensions back. Nothing wrong with this, except as you keep moving forward you've got more and more weight on the front wheel, and this can cause handling problems (hence the tri bike). Forgetting that for a moment, your saddle's movement forward also allows your aero bars to move lower in elevation, that is, you're allowed to make yourself more aerodynamic. Now you've got quite a different position. Your saddle is forward in relation to the bottom bracket, and your road bar's hoods and drops positions are now much closer to you, and they're sitting much lower than the saddle. Your "points in space" are very different in relation to the saddle and to the bottom bracket. They don't work anymore.

Enter the pursuit bar. The idea is to re-create the position formerly inhabited by your hoods, i.e., before you lowered your road race bars to make yourself more aerodynamic. The irony is, people are fain to give up their road bars because they covet their hoods position. But when you lower your bars, you may keep your hoods, but you lose your favored hoods position (and you entirely lose your drops position). The only way to maintain your hoods position is to dump the hoods, and the bars on which they're mounted, and go to a flat pursuit bar. Then you'll regain (something close to) your hoods position.

I'm often asked about the utility of having STI shifters on a pursuit bar. I don't like this, because of the technical way a forward tri position ought to be ridden. I'll write about this in more detail in a future installment, but for now I'll reiterate that this is a position which must be ridden at a high cadence—no lagging, or mashing. The need to shift often is paramount, and having the shifters where your hands are is critical.

SADDLE HEIGHT

There are three ways to determine saddle height. Method Three is the subjective method—adjust it until it feels right. This is really the ultimate eventual way. After you utilize objective methods One and Two, you'll always come 'round to Method Three. But you shouldn't start there and besides, your ability to correctly apply Method Three depends upon whether you're body aware and untuitive, and some people are just body-deaf (or whatever the body-awareness-analog is to "tone-deaf").

This leads us back to the objective methods. Method One is to use a multiplier of one's inseam. Stand on the ground, straight-legged, and place a book up into your crotch, about where you figure the saddle will rest. measure this distance to the ground. Multiply this by .885. Some people use .883. Personally, I don't like this method, because of the imprecision of where the crotch actually is; and where to measure to on the saddle's top. I also think that for steep seat-angled tri bike riding the saddle ought to be slightly higher than for road riding. This remains, however, the predominant way to measure saddle height.

Method Two is to consider the knee angle when the pedal is in its lowest position. But first there are a few things I need to make clear. There are two places on the foot to which you're going to measure. When you're determining the location of the bottom of the pedal stroke, this is measured to the pedal axle, and while the differences are minute, and for the purposes of measuring knee angle, I don't like to consider 6 O'Clock the bottom of the pedal stroke. I rather prefer it to be that point where the crank arm is parallel to the line drawn up to the greater trochanter (i.e., more or less parallel to the seat post). If you consider the red line in the adjacent diagram, this is the position in which the knee angle ought to be measured.

But once your leg is in this extended position, you'll now start measuring to a different area. When determining knee angle you're measuring to the maleolus.

Using the bony protrusion of the outside of the knee as the angle's apex, draw a line to the greater trochanter (bony protrusion of the hip) and to the maleolus (bony protrusion of the ankle). The angle formed ought to be either 145-150 degrees, or 150-155 degrees, depending on whom you talk to. For road riding, I think 150 degrees sounds pretty good. For tri bike riding I like it closer to 153-155 degrees. Perhaps increasing the angle one degree might be roughly equivalent to increasing the saddle height by one millimeter, though it's going to differ depending on the height of the rider.

The tricky parts of calculating saddle height by Method Two are: 1) you really need a second person to do this; and 2) your pedaling technique is going to effect this—if the aspect of your ankle is not correct during the pedal stroke it can cause your seat height measure to be off. If, for example, you're pedaling too much with a "toes down" aspect—if you have to stretch to reach your pedals—you might think your seat height is correct by virtue of your knee ankle when in actuality your seat would be too high.

On the other hand, the nice thing about this method is that it takes into consideration the height of your cycling shoe, pedal and cleat, where you sit on the saddle, any shims that correct for leg length discrepancy, and your crank length. It also takes into consideration any influence exerted by your pedaling technique. So I guess I like this method better.


What do I mean by "influence exerted by your pedaling technique?" I tend to ride with a fair amount of "heel drop." I also seem to read that heel drop, or lack thereof, is a matter of personal preference. Fair enough. But whatever your preference, it's going to make a difference in your saddle height. If my heel is dropped more than yours at the bottom of the pedal stroke my saddle needs to be slightly lower in order to maintain this 150-155 degree knee bend.

What influences heel drop? Your power application throughout the pedal stroke, your desire to utilize your calf muscles—a somewhat insignificant muscle group in pedaling, but of some utility—and your cleat mount (the more forward your cleat, the more you can recruit your calf muscles).

DETERMINING WHICH POSITION IS BEST

Now we get to the meat of it. This is the most difficult part, and if you're a bike fitter it's the part requiring the most skill, in my view. I don't mean the act of executing a proper tri bike fit on, say, Tim DeBoom or Peter Reid. That's easy. That takes 20 minutes, or ought to. The skill comes in determining whether a subject ought to be positioned like Peter Reid, or on a road race bike with STI and shorty clip-ons, or somewhere in the middle. And if it's in the middle, where in the middle?

T
he hard part is figuring out just how aggressive one's position ought to be and can be. The devil of it is, you can be positioned at 74 degrees of seat angle, 76 degrees, 78 degrees, and at 80 degrees, and in each of those positions you might feel great. If you are positioned too shallow, might you've gone faster if you were positioned more steeply? If you're set up steeply, what will you feel like after three hours in the saddle? I believe the art and science of tri bike fitting ought to be light on the art and heavy on the science—but if there's a place for art, this is it.

The goal is to get you as close to 80 degrees of seat angle as possible. The reasons for this are two. There is the lower metabolic cost associated with riding further forward, as demonstrated by those in the scientific community (and which we've written about elsewhere). By "lower metabilic cost" I mean less recruitment of fast twitch fibers during the pedal stroke, leading to a lower rate of glycogen consumption at a given power output (fast twitch fibers consume glycogen at a rate 50 percent greater than do slow twitch fibers). I admit that it takes a short leap to come to the conclusion at which I've arrived—a tieing together of studies to make a point. My full explanation will be found by following the link above.

Then there is the aerodynamic benefit associated with being able to ride lower in front, which is linked with riding forward (it's hard to ride low if you don't move forward). This requires another leap of faith. It's my assumption that by having one's handlebars lower rather than higher that the result will be a position exhibiting better aerodynamics. Surprisingly, even this is not universally agreed upon. But we'll assume this as axiomatic, and for those who don't believe that lower in front almost always means a lower coefficient of drag, we'll just have to agree to disagree.

Though a lower front end might mean lower drag, it doesn't necessarily mean a lower finish time. There are four mitigators, and each of these mitigators serves to cause one to sit further back than 80 degrees. The major one is comfort. If you can't maintain the position comfortably for the duration of your race, what good is it? In this case it's better to be more rearward. This will mean you'll also be a little higher in front. You'll sacrifice a little bit of aerodynamics. So be it. You'll be better off in the long run (pun intended).

The second mitigator is the "M-factor" and "M" is for Mystery. Yes, Peter Reid, Cameron Brown and Tim DeBoom ride quite steeply. But Cameron Widoff doesn't. Yes, Craig Walton rides steeply—very steep, if you consider not just his bike set up, but where he rides on top of the saddle—yet his countryman Chris McCormack doesn't. Natascha Badmann and Paula Newby-Fraser ride steeply, but Heather Gollnick doesn't. While three-fourths of the world's best triathletes ride steeply, 20-25 percent don't. Why? Is it because they don't know any better, or because they just haven't been set up in a correct steep position?

I don't think this gives them enough credit. I rather suspect it has something to do with levers and musculature. I don't believe riding with a steeper seat angle gives you more power at the same heart rate (a claim I've seen), but I do believe it gives you equivalent power and heart rates while spreading the work around to both anterior and posterior thigh musculature during the pedal stroke. Let me use an analogy...

Imagine a company with too few workers and a lot of work to perform. Some of their employees have to work overtime, and the company must pay time-and-a-half. If they hire a few more employees, the work gets spread around, and the company doesn't have to pay overtime. Let's say, however, that it's the best, strongest workers who're getting overtime pay. Do you hire more workers or pay overtime to the strongest workers you've got? This is the dilemma. Most triathletes find that more employees is the better solution, and as a result everyone on the job has more energy for happy hour after the evening whistle ("happy hour" being the "run" in my metaphor). For some athletes, though, I think evening the work throughout the thigh muscles isn't playing to their strengths. I don't entirely know why.

The third and fourth mitigators have nothing to do with anyone reading this, but I'll mention them anyway, because the subject comes up. There are two reasons Lance Armstrong doesn't ride with a steep seat angle. The first one is, he'll get kicked out of the Tour de France if he does. The rules won't allow it. If your racing was governed by these rules, believe me, you would know it. Only bike racers fall under these rules, and even then not one percent of the bike races in the U.S. are subject to UCI rules. But even if the rules did allow Lance to ride more forward in the time trial, I don't know that he would. There is a risk associated with changing one's riding style for one or two days sandwiched in between the 20-odd days of a grand tour. I suspect that's a risk some grand tour riders are unwilling to take. Keep two other things in mind when using Lance's riding position as a model. First, he's not running off the bike. Second, in his "former life" he did win two national triathlon championships on bikes I provided him—both 80-degree seat angled bikes.

Contemplate the diagrams above, and realize that anywhere along the continuum from 74 degrees to 82 degrees of seat angle are fine. However, there are rules you must obey. First, those two 90-degree angles written of above must be preserved. Second, the more rearward you are the more appropriate are road bars, STI, and a shorter clip-on. The more forward you are, the more pursuit bars and bar-end shifting start to make sense.

Where ought you to be along this continuum? All things equal, the younger, leaner, fitter and lither you are, the more forward you'll want to ride. Also, the shorter the race the more you'll probably want to be forward. If you ride with lesser effort, if you carry more weight, if you're older, if you race a longer distance, and if you're more of a mesomorph (strong, muscly-type) the more you're likely to tend toward a position back from 80 degrees.

Where you eventually ought to end up depends on your subconscious tendencies while riding. Do you always seem to be scooting forward in the saddle? Are you sure it isn't because you're too stretched out, and you're subconsciously trying to "achieve" that 90-degree angle between your upper arm and torso? If you're riding on the saddle's nose in spite of having a proper cockpit distance, you're probably positioned too shallow. Are you always pushing yourself back in the saddle? Are you sure it's not because your saddle's nose is tilting down (a bad idea, by the way), causing you to have to push yourself back because you're sliding forward? If you're almost always sitting on the rear of a level saddle, perhaps you're too far forward. Are you frequently out of the aero position? Again, you're probably too low in front and too far forward—while it's a position that might feel good for short spurts, if you can't maintain it for the duration of the ride, you're just too aggressively set up.

A NEW FORMULA FOR SLACKER-ANGLED ARMREST DROP?

I have a formula for armrest drop, and it is this:

This formula causes a lot of hand wringing, because people just read it and try to conform to it, without following the "rules" that are associated with it. But first, I'll explain it.

Distance "C" is what we're looking for, and it is the distance in height (in a vertical plane) between the saddle and the armrests. If you were to drop a line from the top of the saddle to the ground, and measure it, and then do the same with the armrests, the difference between these two numbers would be the difference in height between the saddle and the armrests. The easiest way to measure it, I think, is to lay one end of a carpenter's level on the saddle, and angle the level over one of the armrests. With the bubble in the middle of the level (i.e., with the level parallel to the ground), measure from the bottom of the level to the top of the armrest with a ruler.

The assumption is that we've already got the seat height established, via the guidelines in a chapter above. We've also got the "cockpit distance" more or less established, that is, the distance from the nose of the saddle to the ends of the clip-ons, because that distance is whatever it needs to be in order for our upper arm and torso to achieve a 90-degree angle. You've then raised/lowered your bars so that your "hip angle" achieves a 90-degree angle, or perhaps 95-degrees, and by virtue of that we don't really even need a formula for armrest drop, because the drop is whatever it needs to be in order to achieve the proper hip angle, right? So, why do we even have a formula for armrest drop?

Only as a double-check. If, after you've positioned yourself properly, you plug your saddle height into the formula and you get a number WAY off from the range indicated by the formula, then you've got to ask yourself why. Perhaps there is a perfectly appropriate answer. Either way, that's what the formula's for—it's just a double-check.

But there are rules and assumptions:

• This formula assumes that you're a very fit, well-trained athlete in mid-season form.

• This formula applies to a position all the way forward along the continuum, which for me means something in the order of 80 degrees of relative seat angle. If you're positioned at 76 degrees and you try to apply the formula above, you might find that the position is too aggressive and—guess what?—you'd be right. You don't have a steep enough angle to justify a drop of that degree.

Here's how it would work, and I'll use myself as an example—I'll present the formula again below for reference.

I ride with about 79cm of seat height (distance "D" in the formula above). That quantity, squared, times .005, equals 31.2. Subtract 79 X .2 (which totals 15.8) and you get 15.4. Subtract 1.5 and that equals 13.9 (we'll call it 14)—and realize all these calcs are in cms. The fudge factor is 1.5cm in either direction, so my armrest drop could range anywhere from 12.5cm to 15.5cm. It is in fact about 13.5cm.

I admit, however, to having a more aggressive seat angle than most (I ride with 80°). What about those who'd like to ride at perhaps 78°, or 76°? What ought their drop be? While I'm not convinced of the utility of this, I'm working with a coefficient-based adaptation of the formula above, where ".2" above increases by 075 for each degree shallower than 80° you'd ride. So, if you rode at 79° the product would be (.2075D), and if you rode at 78° it would be (.215D). Here's the calc for someone riding at 77°:

In this case, if I were to use myself as an example (and if I haven't made a mistake) the drop for me at 77° of seat angle would be about 12cm, and the range would then be 10.5cm to 13.5cm. In other words, if I slackened my seat angle by 3°, I'd probably have to raise my bars about 2cm, more or less. You can see why this would be the case. If I don't raise my bars when I slacken my seat angle, my hip angle will become too acute.

Perhaps adding this whistle to my formula will prove efficacious, though it's too early to tell. I hope, at least, that you see the point, which is that you can't take any of these features—seat angle, armrest drop, clip-on length, base bar type—and consider them in a vacuum. They all must make sense as a construct. I hear, every now and then from retailers, that my formula represents a front-end drop that is too low for the bulk of their customers. Maybe it's because the rest of the fit is bad. Or maybe it's because it's being applied to customers who're being set up at 76 degrees of seat angle. If one takes into consideration the limitations of this formula in its raw form, then perhaps it appears less formidable.

HOW TRI-SPECIFIC GEOMETRIES MUST BE RIDDEN

This topic is not specific to tri bike fit, strictly speaking, but it deserves mention. If your retailer sent you and your mate out the door on a tandem, he'd be well advised to give you a tip or two if you were tandem virgins. Likewise, it ought to be pointed out that your riding experience on a tri-specific bike is not going to be 100 percent positive if you don't take advantage of the strengths of this bike.

By "this bike" realize what I'm going to present below assumes that you're on a tri-geometry bike, riding with a seat angle of 77 degrees to 81 degrees. The shallower you are—76, 75, 74-degrees—the less this section refers to you. In fact, if you're riding below 75 degrees of seat angle it doesn't refer to you at all.

There are just three things to remember, and these points ought to govern your tri-geometry riding.

This is a position which optimizes the use of lay-down, tri-specific handlebars. Any time you're in the aero position, you're on a better bike than a road race bike. Whenever you're out of this position, you'd have been better off on a road race bike. Therefore, you better like your position, and be prepared to be in it almost all the time.

Imagine skating around an ice rink. What is your intent? To skate quickly, and perhaps race? A nice, long pair of speed skates is made for the purpose. But what if you want to just knock around with the guys occasionally? Jump into a hockey game now and then? Do a few pirouettes? Or just tool around at an easy clip? Clack skates aren't made for that purpose, and you'll find them unwieldy. Likewise, a steep tri-geometry bike isn't made for much else other than going hard at it while in the aero position. Consider this before you adopt this position.

Because of this, there are certain positions that make sense and others that don't. Besides being in the aero position, there is also an intermediate position that I sometimes adopt, something not unlike the "multisport" position described above. I call it a "choke up" position, and it's adopted by moving very slightly rearward on the saddle, choking up a few inches on the extensions, and sitting slightly up. While in this position you'll be able to generate a bit more peak power, and you might benefit from getting out of the full aero position now and then.

Riding entirely out of the saddle is also a usable position, and riding in the pursuit position is fine for descending and cornering. What I often see, but do not at all like, is a sitting-up position with the hands on the armrest pads while seated climbing. The hip angle is now too obtuse, and this is a low-cadence, low-power position. Better to climb either in the aero position, perhaps in the choke-up position, or out of the saddle. Never sitting entirely up.

This style of riding trades high-torque riding for even-powered riding. You won't be able to generate the sort of peak torque in the aero position that you will while in the road position. Your overall power will be the same, but your ability to mash a low cadence, or to accelerate, will be compromised. Therefore, it is imperitive to keep one's cadence up, probably in the 90-100rpm range. It's quite acceptable to climb while in the aero position. You'll be surprised how fast you can climb, although you might not think you're climbing fast unless you're comparing yourself to others of equivalent ability, or your own previous times recorded up a fixed ascent. But you will be able to climb fast. This assumes, though, that you really do keep your cadence up, and this is a discipline that is hard to learn.

If you think about this, a couple of equipment changes appear rational. First, if it's so important to keep your cadence up, it's important to keep your shifters close to your hands. Therefore, bar-end shifting is a very good idea for steep-geometry riding. Secondly, make sure you've got the appropriate gears at your disposal. I'm usually riding 53X39 and 12-27 on my 700c-wheeled bike. On a hilly course I've been in my 39-27, spinning up a hill in the aero position, next to a person climbing out of the saddle in his big chain ring. If that gentleman outruns me it won't be because he was a wiser tactical rider.

"Why?" you might ask, "is it preferable to trade in a high-torque position (riding a 73-degree seat angle bike) for a low-torque position?" Because you don't want to recruit fast-twitch fibers during the bike ride. You don't want to use muscles that burn glycogen at a higher rate. This issue is what separates road riders from triathletes. This is why triathlon is its own sport, and why you can't necessarily emulate what you see in the grand tours, even the grand tour time trials. If you don't have to run off the bike you don't have to worry about the metabolic cost of your bike ride. If you're reading this, it's likely that running is in your future.

This position is most comfortably ridden under effort. The more you're rotated forward and low in front, the more you're riding on points on your trunk that don't have much padding. When you're riding in this position under very low effort, the weight is transfered off the pedals and onto the saddle. Therefore—though it sounds counter-intuitive—the lesser your effort level while in the aero position, the less comfortable your crotch. This doesn't mean you can't ride your tri bike during easy, recovery rides. It just means it's not optimized for that. If you have a road race bike, this is usually a better choice for recovery riding.

Don't take this to mean that a steep-geometry position is unusable for all kinds of riding. It's usable, just not optimal, for all kinds of riding. Likewise, road bikes aren't optimal for all kinds of riding, but they're often used in triathlons anyway. It's just a question of what sort of riding is most important to you, and then adopting not only the most appropriate bike position, but the tactical and technical riding styles that dovetail with that position. When I hear, "I tried a steep-angled bike but I found I just couldn't generate enough power," I find that in most cases it was because the rider didn't understand how steep geometry bikes need to be ridden. He rode his tri bike around town at 70rpms. Of course he couldn't generate enough power.

HOW DO YOU CHOOSE A BIKE AND HANDLEBARS?

If you were in the market for bike for road racing, things would be simpler. Most road bikes are built inside fairly narrow parameters. There is almost no road bike in your size that you can't easily make fit.

Not so in triathlon, where a wide variety of options exist. There are "tri bikes" with 74-degree seat angles, and with 80-degree angles. At 6'2" in height a tri bike in "my size" might have a 60cm top tube or a 54cm top tube. Certain bikes styled as tri bikes are in fact nothing more than road bikes marketed to triathletes. How does one go about choosing? There are some guidelines that might help.

You can make any bike fit. I'm reminded of an Arnold Swarzenneger movie in which he had to rip out the seat of a small car he was "borrowing" in order to fit inside it. Better if he just had to adjust the seat back a bit. The trick is to find the bike that takes the least amount of jury-rigging to make fit.

Your first duty is to figure out which position is going to work for you—where along the continuum (spoken above) you'll need to be. There's nothing wrong with being all the way back, i.e., to ride in a road race position. You'll have a difficult time riding comfortably with a full tri bar, however. Better to get a shortie bar.

At this point I shall digress slightly, and gently scold many of you who'll read this. As I write this I'm fresh back from the Wildflower Triathlon, where I had the opportunity to ride past perhaps a couple of hundred athletes. These are good athletes. You don't enter the half-Ironman version of this race unless you're reasonably fit. There were four things I noticed: that a great number were on traditional road bikes in a road configuration; that the overwhelming majority were riding with road bars and clip-ons; that most had full tri bars (not shorty bars); and that a good half of all the riders were out of the aero position and on their hoods, even though riding on the flat roads.

The greatest number of athletes I encountered were riding on the "backstretch" of this course, the straight section from mile-20 to mile-35. This entire stretch was ridden into a headwind. There was every reason to be in the aero position and no reason not to be. Why were so many riders not where they ought to have been?

My view is that after 30 or so miles of hard riding it was just no longer possible to sustain an uncomfortable aero position. Riders couldn't take it any longer.

Yet it's these same riders who complain that they, "ride a road bike because it's to uncomfortable to ride a tri bike for 56 miles." Notwithstanding that I, with my 80-degree tri bike, was out of the aero position for perhaps 20 seconds during the entire ride, I'll stipulate to that point. Maybe a road bike was a better bet for all those people. But heavens, it can't be right if you're not able to spend 25 or 30 miles in the aero position without abandoning it, right?

To that end, I'll share a letter I recently received from a reader, who writes the following:

"If you have time I have a question for you. I just read your update to the Tri Bike Fit. I seemed to understand the bike fit article better than when I read your original article. I'm riding a Litespeed Saber. I had what I believed was a professional fit to my bike. It cost a professional amount, $200, but I'm not sure of the benefit to me as a triathlete. The fitter, [I'll omit the name, it was a well-known tri bike fit professional], had my seat as far back as possible on an already set-back Easton Carbon seat post. His rationale was that the plumb line from behind my knee cap was too far forward of the pedal spindle when at the 3 and 9 o'clock positions. His goal for my knee angle was 140 - 145 degrees. With his setup I could not ride in the aero position more than a few minutes. I was uncomfortable. I kept sitting up and riding on the bullhorns. This totally negated the benefit of my tri bike. I moved the seat forward after a couple of weeks and can ride in the aero position as long as the terrain allows. After reading your article, I move my seat forward to be in line with my seat tube and raised the seat to achieve 153 degrees in my knee angle. Now finally to my question. Do you concern yourself with knee position over the pedal spindle? If so, do you use center mass of the knee joint, behind the knee cap, or the front of the knee cap?

"Thanks for your time and the updated article. It has provided more useful info than the fitting I received."

This person could've used a laid-back position, but not with the full aero bar at its full extension, as the bike was originally spec'd. At least, if you're going to choose a road bike and road position, choose an aero bar that allows you to maintain that 90-degree shoulder angle. My favorite has been the Profile Design Jammer GT, but there are others, such as a couple of designs shown here by Deda Elementi (I'd shorten the bar above quite a bit more than the photo suggests, and I may or may not even use the armrests—I might just wrap the tops with a couple of rolls of bar tape). I don't think the perfect aero position bar for road position riding has yet been invented, but there are some that make a decent attempt—examples would be these by Deda, the Profile Design bars, and Cinelli's Spinaci and Spinacissimi.

Should you desire a steeper-angled bike, you can either choose a bike that is already sufficiently steep, or a shallower one might work if it's also long in the cockpit. I, for example, like my bikes steep, like 80 or 81 degrees. I also like them low in front, and short in the cockpit, like 55cm or 56cm of top tube (my road race bikes have 60cm of top tube). I can make a 76- or 77-degree bike work, however, if it's got 58cm or 59cm of top tube. Certain QR and Felt bikes are good for me in this respect. By the time I move the saddle forward (by any number of means) the bike is both steep and short enough for my liking.

This assumes, though, that the front end is low enough. It's hard for me to get my bars low enough on a 700c-wheeled bike if the head tube is longer than 13cm or 14cm. I can live with a 15cm head tube if its got an integrated headset, because now there is 15mm to 20mm worth of headset "stack" that I don't have to worry about, because the headset paraphernalia is inside the head tube.

So what do I do if I want to ride an Aegis Trident in my size, which has 17.5cm of head tube and a non-integrated headset? It's hard to get my bars low enough, and I'm pretty well stuck unless I also decide to ride with a lower-profile aero bar. I can ride a Trident quite nicely if I've got a HED aerobar or a VisionTech—assuming I'm not using any armrest riser kits, or Vision's plush aftermarket armrests that raise the elbow position quite high above the centerline of the base bar.

Conversely, if you're thinking of retrofitting your existing bike with one of these slick aftermarket bars, consider what aerobar you're currenty riding. A Profile Aerolite has armrests that sit about 7cm above the centerline of the pursuit bar, and other Profile bars, and Syntace bars, have about 6cm of rise. The HED aero bar's pads sit 2.5cm above the pursuit bar's centerline. So, if you take off your Profile Aerolite and replace it with the HED, your arms are going to be sitting 3.5cm lower to the ground (all other things equal). You'll need a new stem, or something, if you want to achieve your previous position.

This might seem complicated, but it's not. It's just stuff you need to keep track of. With road race riding, there are a lot of road bars out there, but from a positioning perspective a bar's a bar. With tri bars, as with tri bikes, there are wide variations in position across every axis. When you're considering a bike, where along the continuum is your desired position? Make sure the bike, and the aero bars, allow you to achieve the 90-degree angles written of above while in this position.


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