I look down to see what is wrong. My rear wheel has slipped and the tire is rubbing against the frame. Racers are flying past me as I work to correct the problem. I have to laugh because I am riding a single speed bicycle — there are so few moving parts that it is almost impossible for anything to go wrong. But I took a risk and used a wheel with a quick release skewer instead of the single speed tradition of a bolt-on axle.

I readjust the wheel and continue on the trail. On the next hill, it slips again. I stop to fix it and more people pass me. One more time, and the same thing happens, but when I try to tighten it this time, the skewer lever bends in half. At least I am prepared for this worst case scenario — I have a spare in my Hydrapak. I am now staring at the entrance of the singletrack...in 400th place.