Has anyone out there had any problems with the stock tires rotating on the rim. I've had it happen 3 times now. The first time I thought I was nuts, the second time I started to catch on, last time I maked the wheels and tires and actually measured how far they rotated. Each time, the tire pressure is at 15-16 lbs. I've had no problem with the pressure above 18 lbs. This is during exteme climbing in rocks. Traction really hasn't been a problem, but the stiff sidewall has been. A couple of tires have rotated almost half a turn during a long weekend!