Crank length is often set from height. That falls short. Whether a crank suits you shows mostly in how your hip and knee work at the top of the pedal stroke.
What affects crank length
At the top of the stroke, the angle in the hip and knee is at its tightest. A crank that is too long can close that point down, crowd the hip and make a calm position harder. How much this matters depends on your mobility.
- your mobility in the hips and knees
- your position, especially when it is low or aerodynamic
- your type of riding, such as road, triathlon or gravel
- how calm the pelvis stays through the stroke
Why shorter cranks often help
Many riders get on better with a shorter crank because the hip gets more room at the top. But that is not an automatic advantage. It comes down to what your movement and your goal show.
How I assess crank length in a bike fit
I do not look at crank length on its own but together with saddle height, position and mobility. Only when it is clear that it really limits you does a change make sense.