Monday, September 27, 2010

More on tires

This weekend was not a good tire weekend for me. Both cars had punctured tires Saturday. Sunday, I finally got around to mounting Stan's Raven tires on my 29er. I bought these tires with one purpose in mind: fast non-technical courses like Ironcross, Leadville or the VT50. I was primarily concerned with rolling friction. Reviews suggested Raven's had an efficient casing. The barely-there tread helps too.

Published weights of tires are usually bogus. Tires always weigh more.  The Raven's are claimed to weigh 520g, which is silly light for a tubeless ready 29" tire. I don't even own any tube type 26" tires that are this light.

When the Raven's came in several weeks ago, I immediately weighed them on a tool every cyclist has, even if they don't wrench their own bikes - the gram scale. First tire, 520g exactly. Nice. Second tire, 470g. Uh, oh. I suppose Stan's lists this as the lower limit for the tire, so maybe it is not a defect.  The sidewalls of both tires were little more than onion skin. They were flimsier than Michelin Pro 3 Race tires I run on the road. I had extreme reservations using these tires for any kind of riding, let alone a 62 mile cyclocross race on fire roads, ATV trails and singletrack.

I pulled the Bontrager 29-3's off. These tires hook up quite well on the trail, but they are quite slow on pavement and hardpack. They take noticeably more energy to wind up when accelerating too. I put the heavier of the two Raven tires on the rear wheel. An extra generous serving of Stan's sealant was poured in. As I do with all tubeless tires, I try the hand pump first. This wasn't even close. I fired up the compressor, waiting until it hit 125psi.

I could not get the bead to seat. You'd think a Stan's tire on a Stan's rim would be a perfect marriage. Nope. I spent at least 10 minutes with the compressor running continuously trying to get even the slightest bit of air in the tire. I kept loosing sealant. Finally the bead caught. What a PIA.  I shook the tire all the way around to spread the sealant around. There were numerous little pinholes with white bubbling out. My reservations about these tires grew.  I worked on the front tire next, taking almost as long to inflate. They are rated to 40psi, I stopped at 35.

I figured if I was going to race on these essentially innertubes with a decorative tread pattern on them, I would have to give them a serious test. I thought the probability of walking out of the woods would be high, so I picked a place where I would never be too far from my car. Willowdale State Forest in Mass would work. For the most part, the trails are buff at Willowdale, but there are many rooty sections and a few follow glacial eskers, which are comprised of sharp, rocky material.

Not two miles from my house, I heard a sudden psfffffffft. What the...  I pulled into a state line beer store, opened the hatch, and too my horror, the rim beads of both tires were leaking. If I didn't address this then and there, the tires would go flat and I'd never be able to inflate them without a compressor. I removed the wheels and proceeded to shake the crap out of them to move more sealant around. I'm sure patrons of the party store wondered why this skinny old white dude in spandex was having a hissy fit with his bike tires. The leaking stopped for the time being. I kept the windows up so I could hear another leak if one started.

I got to Willowdale with air still in the tires. I did have to top them off again though. I hadn't been to Willowdale since late last fall. The trails were dry and almost as firm as concrete. You could fly. I putzed around at first, as I was pretty wrecked from the 50 miler the day before. About 40 minutes in, I felt the rear tire bottom out hard on a rock. It didn't cut. But it was down to about 15psi. I topped it off again.

A while later I met up with this couple. They both could really move. They showed me a new trail that had just been cut this summer. Very sweet stuff. The woman asked me to ride ahead of her. This made me nervous, as she had no problem staying on my wheel for a while. No more putzing around. I chased her significant other around at near race pace on a trail they knew and I've never been on.  Forget about onion skin tires. I feared a meet-up with a tree.

I finished a two hour ride with all limbs still intact. The tires held air for the rest of the ride. There is hope for them. The Raven's do feel exceptionally fast, probably faster than the Racing Ralph CX tires I used at Ironcross last year. The supple casing allows for surprisingly good grip.  They also wind up about as fast as heavy 26" tubeless tires. It made my Superfly feel quite snappy.  The tires have a very lively feel too, kind of like latex tubes in Michelin Pro 3 Race clinchers. That tells me the casing returns energy from impacts rather than absorbing it. This is good if you want a low loss tire. Not good if downhill is your gig.

The first time I raced Ironcross, I was on my Dean hardtail. I did well that year, but it was a much more brutal course, probably more technical than the VT50 course is today. The past two years I rode my Ridley CX bike.  To try something different this year, I'd like to try a MTB again. I know there are several sections I can ride faster on a fat tire bike. The question is, will being on a fat tire bike get me popped out of the lead group sooner, such that I'll lose significant drafting benefit later in the race? Hard to say. Of course, if I flat, the experiment will be a failure. I haven't flatted at Ironcross yet. What usually gets riders are the embedded rocks in 40mph fireroad descents, not the gnarly two mile singletrack descents.

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