Originally Posted by
taras0000
At 100 RPM footspeed =
165mm cranks = 1.727876 m/s
170mm cranks = 1.780236 m/s
175mm cranks = 1.832596 m/s
It's a 3% difference between the first two, and a 2.9% difference between the second two. Seems small, but if you thought about it in terms of gearing (to slow your foot back down), that's roughly a 2 tooth increase on the chainring if you're using 48-51 tooth rings.
Thanks for illustrating that!
houleskis, I've raced a full season on 165, 167.5, 170, and 172.5mm cranks, and the differences are subtle but significant. It affects your riding style (spin vs mash), fit (shorter cranks allow you to lean over more), and most important (as taras mentions) your gearing. As the cranks get longer, you gain more leverage against the chainring/cog/wheel system. And as they get shorter, you lose leverage.
Some aren't sensitive to crank length, meaning that they can't feel the difference. But, the differences a real and measurable.