Originally Posted by
brawlo
Now that's interesting. I've never been bothered to crunch the numbers. Going back to what I said about foot speed or tangential velocity limitations, my own experience kind of blows that out of the water then. Theoretically, going from 175mm cranks to 165 cranks at max 180rpm (175's) should only net me about 11rpm more. Obviously there's a whole lot more to it than simply foot speed. I hit 216rpm in one roller derby round where my highest cadence on 175s is around 180
Yeah, there is.
Basically, 165s allow you to get closer to what you are capable of doing in terms of rate of muscular contractions. 175s are holding you back.
I bet if you put 165s on your track bike, you can do the "running on the pedals" thing where you do a standing lap out of the saddle.
Not saying you would be faster, but holding high cadences out of the saddle is difficult on longer cranks.
Also, with shorter cranks, your pedal stroke shifts at certain RPMs from a "down-down-down-down!" thing to a "forward-back, forward-back!" fast shuffle, thus engaging different fast twitch muscles.