November 15, 2007

Twins and Tubeless Tire Setup

They finally arrived and are ready to rock for this weekend's USGP in Trenton, NJ.
Weight - 16lbs 10oz. That's almost 3/4 lb lighter than my previous setup.

The reason being I get to run the FSA K Force lite crank with ceramic bearings. Double chainring setup this year with a 38/46 and a 12/27 in the rear. Down the road I might set up one bike with a single chainring, but for now they are both double.
I also went with the new Tektro cr720 brakes. There is a ton more clearance between the rim and pad with this setup and these brakes are some of the lightest with a lighter lever feel over other wide profile brakes. Last year I had the Cane Creek cr5 which were the same weight and had a really good feel, but when the ground was wet I could hear the brakes hitting the rim when I stood up to pedal because of the small clearance and the wide profiles don't do that.
I had some people asking me about my tire/wheel setup from last year so I'll explain it. This year I am using Tufo Flexus tires on Zipp wheels which is extremely light and stiff. Last year I ran Bontrager xxxlite clincher rims with Michelin tires - tubeless. The secret was to set the rim up with a 26" Stan's rim strip and Stan's sealant. The result was I could run a little lower pressure over standard tube and tire because I didn't worry about pinch flats. On most cross courses this is pretty much the only reason to get a flat, or, if you live out west or down south the goat heads. This setup should help eliminate both of those. I know at the Boulder cross races last weekend a bunch of the top guys were running a setup similar to this to avoid flatting from goat heads. Now that Shimano has tubeless rims it should make this setup easier, I think Adam Craig is running it currently and he seems to be going alright.

A few tips on setup. Run a band of electrical tape around the rim first to cover the spoke holes. Then wet the rimstrip with water so it's easier to work with and slowly and evenly stretch it around the rim. It takes a while to get it even the whole way around so be patient. Eventually you will need to take a small screw driver and push the rimstrip under the bead so it sit evenly the whole way around. Finally, tuck in the rubber on both sides of the valve, this will be the hardest spot to get. It should look like the above picture. It took close to an hour per wheel to get it set right.

I had the best results with Michelin Mud 2 tires and I think these are the best tread pattern out there, especially in the mud. I was able to run between 36-42 pounds at most races. It is better to run this setup on a wider profile rim as it will give more support to the sidewall of the tire and reduce the chance of folding over the tire and 'burping' the air out. I only had this problem once when I preloaded the rear end to bunny hop on an off camber area and then again earlier this season in Michigan. It is possible to do with this setup, usually the drier and faster the course is, the harder you must pump your tires so that the ground doesn't rip the tire off.

The difference between this and a tubular setup is that a tubular tire is much more supple at light psi, yet the sidewall does not get weaker as the pressure goes down. It must have something to do with the 440tpi casing on the Tufos. With the tubeless setup, at lower pressures, mostly below 36 for me, the traction would be good, but when standing or sprinting, the tire would feel extremely soft and mushy, something the tufos don't even below 30psi.
Last year at Nationals I ran too low a pressure and could not corner hard at all without burping the tire, quite irritating and distracting while racing, but if you are concerned about pinch flatting or thorns/goat heads, this is the way to go if you run clinchers.


Echelon said...

i think i like the XO better. at least you have sweet wheels for back up.

Rowbear said...

Gee whiz. I'm jealous