I've googled this topic until the cows came home. I've watched the juniors wrestling heavy mtb bikes. We have a Fuji Ace 24". We checked out the Novara 26" bike. Both of these bikes are heavy. The Fuji only allows a 24"x1" tire. We could put treaded tires on it and it might work. The only solution I've been somewhat satisfied with is a 24" bmx crusier. The problem with this bike is a) single speed, and b) only a rear brake. Maybe the single speed is not a problem - my son usually spins like mad. If the bmx cruiser would work then we could also use it at the bmx track. Would the USAC officials allow a bmx cruiser in a junior race? Can I get some opinions and advice? Much appreciation to be had. Thanks.