Originally Posted by
mangpress
the thing with crank arm length and gears is that, longer arms <i>should</i> effectively give you more leverage over the gear while a shorter arm gives you a smaller circumference to spin through.
sprinters tend to run shorter cranks, while pursuiters and endurance riders (on the track anyway) run longer crank lengths.
there is little to suggest any of this will affect your performance any more than drinking goat milk prior to a crit.
the way i see it, the standard gear inch calculation describes the wheel rotation per crank rotation, and each crank arm length will have a different feel at a given ratio. the gear inch calculation can be corrected for feel by utilizing the proportion of crank arm lengths. with identical overall tire diameter and ratio, i know that the distance traveled per rotation will be no different with different crank arm lengths, but if one is to compare how ratios feel, arm length must be accounted for. though distance per arm rotation is identical within a ratio, i think crank arm length has an affect on performance. fit is likely the most important factor of performance with an arm length, but assuming one has no preference between two arm lengths, different arm lengths will feel and perform differently. i would guess that longer arms have a greater mechanical advantage for efficiency while shorter arms can hit high revolutions more easily because the pedal travels a shorter distance per revolution.