crank length for new bike

[OakLeaf]

I think it's the femur and the femur/tibia ratio. Whole leg length doesn't tell you much. But it's kind of theoretical since you can't measure any of that accurately without an X-ray. Then I guess pedaling style goes into it too - whether she ankles a lot, and if so, foot size probably matters as well.

The main thing you want to look for IMO is, when you set the seat height so her foot is in the appropriate position at the bottom of the pedal stroke, is her knee bent more than 90 degrees at the top of the pedal stroke? I'm pretty strong about that, myself. You hear it over and over and over again when you do squats, lunges, step-ups or step aerobics: do not bend your knee more than 90 degrees when it's weight bearing. Then nobody pays attention to that when fitting a bicycle

Does she have the luxury of trying out various sized cranks, or a fitment machine with variable crankarm length? What RPM can she spin smoothly with the longer cranks vs. the shorter ones? Has she ever had knee trouble in the past?

... and if she does wind up wanting a 170 mm triple, does she want the Shimano 105 that came stock with my bike?


- Oak, 5'3", 51 cm Cannondale feminin road frame (which is slightly tall per the standover height, but good top tube length and perfect for my pedal stroke with just over 11 cm of seatpost showing), sz 40 Specialized shoes, 165 mm cranks, knee problems if I use longer ones.