Mountain Bike Crank Length Calculator

If the store does not offer a bike fit then get fitted elsewhere so you know your appropriate crank arm length.

Mountain bike crank length calculator. Why your mountain bike crank length is likely too long with few exceptions most xc and trail oriented mountain bikes shipped today come with 175mm cranks. Thus if you know the chainline is 48 5 mm with a 113 mm isis drive spindle length then you automatically know that if you use a 118 mm isis drive spindle length your chainline will increase by 2 5 mm each crank moves outward 2 5 mm for a total of 5 mm. While some brands spec 170mm cranks it is often only on their smallest sizes. When it comes to mountain bikes bike crank arm size isn t nearly as crucial.

A good bike fitter will help you find the best crank arm length for you. Normally fit adult riders should use cranks which measure about 20 of their effective leg length rounded to the nearest 5mm whereas growing children can safely increase this figure to 22. Some bike fitters will have an adjustable crank so the pedal can be moved to simulate crank lengths from 155 185mm. Go into any mountain bike shop and chances are every bike in there will come with 175mm or 170mm crank arms with 175mm usually found on m xl sizes and 170mm found on xs s.

Femur length in inches should be the same as crank length in cm alternately femur length in cm divided by 2 54 equals crank length yields the same result this is based around the idea that the upper leg is the major lever when applying force to the pedals and that the lower leg is the connecting rod and plays little part. Bicycle cranks may vary in length to accommodate different sized riders along with unique kinds of biking. You can try this during a bike fitting. However the evidence leans towards mountain bike crank lengths being too long in general.

If you really want to calculate your perfect crank length use this formulae crank length mm 0 0123x squared 4 8121x 293 8 where x inseam gt height in cm.