What is Crank Length?
The length of the crank arm as measured from the center of the bottom bracket to the center of the pedal spindle.
Why does it matter?
Crank length can have an important effect on a rider’s biomechanics; a poor-fitting crank can negatively impact performance and result in injury to the rider.
While many bit fitters agree that crank length should be proportional to body size, there are numerous methods for determining ideal crank length and many cases in which a rider’s individual biomechanics require a deviation from the norm.
Aside from rider fit issues, longer crank arm length can also increase the risk of toe overlap and pedal strike.
Most of the bike industry specifies proportional length crank arms that are shorter on smaller bikes and larger on larger bikes. Standard lengths for production bikes typically range from 165-175mm although shorter and longer cranks are available aftermarket.
Crank Length Options
Crank arm length exists in several places at Bike Insights.
When calculating things like Toe Overlap, we will first use the default crank arm length in the base build (e.g. what a complete bike ships with). If a build is then customized, we will use the custom crank arm length for these calculations. If no values are present in either of the builds, we use the default value of 170.