Originally Posted by
cwcaesar
While on the subject of replacing the cranks, I am wondering if I should go to a shorter crank. I recently measured myself and found that I am right at a 31" inseam, or maybe a smidge under; or about 78 cm. According to the web searches I have done, this is the only measurement that needs to be taken for the crank length. And according to this I should be running a crank in the neighborhood of 162.5 to 170. I currently have 175mm cranks and I find it difficult if not impossible to spin over 85 rpm without bouncing. Should I be looking at a shorter crank arm length in my search? Would these shorter cranks help me to spin higher rpms more comfortably?
I was under the impression that bouncing usually meant that your seat height was incorrect or that your pedal stroke wasn't smooth. I've heard that short cranks are easier to spin, but not sure I believe it. I have a 32" inseam and own cranks that are 170mm, 172.5mm, and 175mm. I honestly can't tell much difference between them. I can spin all of them at 100-120rpm with the seat height set appropriately. For me, spinning was about having the right gearing and then practicing with a higher cadence. Took me about a season of steady practice to work up to a smooth 120rpm cadence...