Bike Forums - View Single Post - The Effect Of Crank Length On Performance
Old 10-25-18, 10:20 AM
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Originally Posted by colnago62 View Post
I have both 165mm and 170mm cranks and have used both at different times in my riding at the velodrome. I used to feel that the 170 allowed me to turn a larger gear and the 165 cranks allowed for more cadence. I had no research at all to back my opinion up with, I think it was something told to me a long time ago. Is there any truth to those two beliefs?
These are both true. In one of the other threads around here, someone ( I think Carleton) calculated the gain ratio difference between 165 and 170 cranks, as well as the difference in foot speed given the same rpm for each crank. If I remember correctly, the gain ratio wasn't a huge difference, but the foot speed differential was greater than one would think.

As far as the the gain ratio and "feeling easier", the cranks do give you a tiny increase in leverage, but that 5mm might be able to be offset by the fact that your hip angle opens because your TDC drops 10mm, which moves your weakest part of the pedal stroke into a stronger range of motion, and shortens the the window of time you spend here because you reach fuller feg extension earlier in the pedal stroke.

In other words, although longer cranks give you more leverage at the pedal interface, shorter cranks allow more of the pedal stroke to be spent in a more powerful muscular range.

Last edited by taras0000; 10-26-18 at 10:07 PM.
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