My understanding of the rules for the alleycat is that all wheels must be less than 20", and folding bikes or other small bikes designed for adults are not eligible. Otherwise, any other bike mods are OK. For minibike competitions on kids bikes, that usually means longer cranks and larger chainrings for starters. The tour de bomb downhill on Sunday is open to all bikes. The olympics are a blast even if you don't enter any events. Hope to see you there!