Besides actual frame size, it seems like tire clearance is one of the most limiting factors on the bicycle frame. You might be able to change out every component on the bike, but still be stuck with 25mm tires.

How come the vast majority of consumer bikes in the US have such tight clearances on anything that isn't a mountain bike? Is this a result of the racing industry's effect on the other 99.9% of riders? Even many bikes geared towards commuters, tourists, and weekend riders have limited tire clearance.

Cheers.