with my bike i have 45,46,47 tooth chainrings and 14,15,16 and a 19 tooth cogs. lately i've been using a 46x14 or 47x14 at the track and ride over to the track on a 46x19 or 47x19. with the 46x14 the chain is at the very back of the dropouts. with the 19 it's pretty close to the front of the dropouts. thats a 5 tooth difference. my bike is really old and has long campy dropouts. some of the newer bikes look a little shorter so you might not be able to get that big of a difference. the other choice is to have two different length chains to get all the gear choices you need