Clearance depends on the crank, the frame, the pedals, the rider’s technique, and the type of event/ride. In the ideal situation, the frame is built to fit both the rider and the crank for the type of riding they do; then the bottom bracket height can be adjusted to provide the desired pedal clearance. At Zinn Cycles, we generally build the bottom bracket on a frame getting a 200mm crank 25mm (one inch) higher than the BB of a frame made for 175mm cranks.The longest crank we recommend for somebody using a stock frame is 200mm, and only if they are not even thinking of racing criteriums. In a criterium, more power is worthless if you open a gap to the next rider in every corner that you have to close at great expenditure of energy because you had to restart pedaling later to avoid hitting your pedals on the road. I think it inadvisable to race criteriums on a stock bike with a standard (265mm) bottom-bracket height using any longer than a 175mm or 180mm crank.We do have successful tall masters racers competing on our cranks up to 195mm who must use a stock frame due to sponsor constraints. But they adjust their riding style and choice of events accordingly.
For anybody who has a question about whether they’ll have enough pedaling clearance if they buy a crank from us, we recommend taping a styrofoam block the thickness of the length difference they are considering to the bottom of their pedals and notice if or when they touch it to the road.
