NoTubes Alpha Pro Wheelset - http://nyvelocity.com/content/equipment/2011/notubes-alpha-pro-wheelset

NoTubes Alpha Pro Wheelset

Mon, 09/19/2011 - 4:43pm by Andy Shen

Update:Demo Program Launched

New Yorkers curious about these wheels and/or tubelessness (tublessity?) can now demo them for free via iFIXBYX. Demos last 1-7 days, and reservations can be madehere. If you've been contemplating tubeless here's the perfect opportunity to try it free of charge. Most who do never look back!

Original writeup below:

When I first heard Stan’s NoTubes made 1200g aluminum wheels, I assumed it was a case of a company playing fast and loose with durability and strength by spec’ing ultralight components. But I should’ve known better. After all, Stan Koziatek is the mad scientist who singlehandedly took on the mountain bike UST tubeless standard. Not surprisingly, there’s a lot more to the Alpha Pro wheelset than just light weight.

The wheels are built on American Classic hubs, 18 DT Supercomps radial in the front and 24 3 cross/radial on the back. There are 16 drives side spokes to 8 non drive – this puts as much tension on the non drive spokes as the drive side. This should lessen the chances of those spokes breaking, as well as help them maintain tension. There’s a 190lb rider weight limit (I’m 158 lbs).

The Rims
The ZTR Alpha 340 rim (which, oddly enough, weighs 350 grams) is designed to keep the tire in place with a tight interface with the rim bed, rather than the bead hook. (This isn’t that radical an idea, Paul Lew was working on a prototype rim like this back in ’09.) In fact, the bead hook is almost completely dispensed with, leaving just a little nub. NoTubes calls this BST (bead socket technology), and you can read all about it here.

Here’s the Alpha rim (it comes pre-taped for tubeless) next to a Ksyrium. With its minimal hook, the Alpha’s outer width is comparable to the narrow Ksyrium, but its 17.1mm inner opening is in line with wide rims like the Hed Ardennes (17) or Zipp Firecrest (16.3). Also note the high shoulder, just 3.5mm from the edge of the rim. The higher shoulder makes a snug fit against the tire bead, so much so that the tire is almost airtight as soon as it’s mounted. You can slowly inflate it with a floor pump, no soap, no sweat, no drama, no compressor needed.

Running Tubeless
In fact, inflating tubeless tires on these wheels is pretty fun. While alignment can be tricky on normal rims, it’s almost foolproof with these rims. If a bead isn’t straight at 90psi, add more air and watch it slowly ooze into place right before your very eyes.

The higher shoulder pushes more tire above the rim, making for a higher volume tire. Hutchinson Fusions measured 24.4mm across on the Alpha, 23.9 on Zipp Firecrest, and 22.6 on Zipp 101 (I don’t have a mounted Ksyrium handy, but I remember that it was about the same width as a 101).

What’s the big deal about wider, higher volume tires you say? Two things: At the same psi, a wider tire makes a wider contact patch. Compared to a long narrow contact patch, a wider patch doesn’t extend as far ahead of the wheel axis and so has less leverage to push back against forward motion, resulting in lower rolling resistance. Secondly, you can run lower psi’s with a bigger tire for a bigger contact patch and more suspension on rough roads. This sucks up road irregularities so you retain more forward momentum, and keeps you planted when you corner so you don’t drift wide with every bounce.

NoTubes also contends that tires adopt a rounder cross section with their rims. They say the bigger hook on traditional rims force tire sidewalls into an s shape, which makes it less round and less secure leaning into turns. In theory the more convoluted sidewall shape forces the tire to flex more under load. And since nothing ever rebounds with 100% of the energy returned, a tire that’s flexed more will suck up more of your precious watts.

I traced the tire profile on the Alpha, 101, and 808 with a laser (yeah we got frikkin’ lasers) and didn’t find a perceptible difference in roundness. My guess is that any reduction in rolling resistance from less sidewall flex is minimal (as it is, rolling resistance is a smaller factor compared to air resistance and gravity).

Here’s the Alpha tire overlaid on the 101 tire (Alpha in red). It’s wider and taller, but doesn’t appear any rounder as it exits the rim.

Here’s the Alpha, again in red, overlaid on the 808. The two tires are closer in cross section, with the Alpha a tiny bit bigger. Once again, the Alpha tire isn’t perceptibly rounder.

The Ride
Enough with the setup, time to ride. The NoTubes team rave about how well these wheels corner, saying that they can dive inside other riders in NRC crits. My goal was to beat these wheels up a bit and try to push the limits of their cornering ability. I trained on these wheels every ride for about a month, and I also got in a race at Floyd Bennett Field on the Thursday short course, a triangular course on crappy tarmac.

Paired with Hutchinson Fusions at 90 psi, these wheels rode incredibly smoothly, similar to the wider Firecrests (the Firecrests’ carbon rims muted more buzz) and noticeably plusher than the same tires at the same psi on narrower 101’s. It’s pretty much the closest you can get to cornering the Tron Lightcycle in this mortal coil. They spun up quickly just as you’d expect superlight wheels would, and I didn’t find them flexy at all.

At the Floyd Bennett race I found that I could always dive further inside everyone else in the corners. And since I was hanging on for dear life, I appreciated the fact that I could pedal full gas in the turns to make up ground, never fearing that I was pushing the limits of my traction. A teammate running the same setup had the same experience (being lighter, he ran 80 psi).

15.1 pounds on a 58, no special weight weenie parts.

Things go pear shaped
Here’s where things got weird. The pounding at Floyd Bennett (I drilled some potholes real hard) plus some excursions on cobbled Manhattan side streets knocked the front wheel pretty far out of true. I popped it in the truing stand and found that one spoke was almost slack. Truing a low profile rim with only 18 spokes was a bit tricky, and I had to sacrifice tension balance for trueness. I put a tensiometer to the spokes and was shocked to find that they averaged only about 50kg, about half what you’d shoot for with those spokes.

First of all, this confirms what Rich Sawiris told me: an undertensioned wheel doesn’t necessarily feel flexier, but is less durable. Secondly, it appears that this wheel was laced up and given a quick true, but had somehow shipped without being brought up to proper tension. My 145 lb teammate’s wheels also went out of true pretty quickly, but I also spoke to an even lighter rider who had no problems with hers.

So...?
I really really wanted these wheels to be awesome. They’re quick and light, have an amazing ride, and flat out make riding your bike more fun. And even though I’m able to true them up myself I have to take a pass on them, because I’m not sure of their long term durability (NoTubes offers other wheelsets with higher spoke counts, but with the same superlight rim). I’d recommend them for super light riders on smooth courses, but that’s somewhat oxymoronic since the tubeless setup really shines on bad roads.

My hope is that NoTubes will make a more robust rim, or license the shape. A wider rim would resist torsion much better as well (if you’ve built up an Ardennes rim you know what I’m talking about). American Classic and Mad Fiber have already produced similar rims, so this does seem to be a trend. With any luck rim shape will continue to evolve in this direction and wide, hookless rims will become the standard.