UCI just says no wheels bigger than 29". I'll have to see if I still have that little blue booklet, I suppose I might get a new one when I join up again next year anyway. Seems likely that there is no reason to not allow a CX bike in a normal MTB race. And no, I would not complain about the bumps Corty, this is more for a dirt crit in which the course is hardly technical. I'll stick to the regular MTB for proper XC races.