Optimum Crank Length

Find your bicycle optimum crank length and protect your knees.

This app will allow you to calculate the optimum crank length (OCL) for your bicycle according to your body anatomy. The calcs will take in account the knee angle when the pedal is at the bottom and at the top, to help protect your knees from injuries.

Besides the OCL, this app will give you the "Seatpost Length" and "Maximum Frame Size" for your new crank length. If your bicycle is a road, mountain, trekking, cross, single speed, city, recumbent or even a trike or a velomobile, the OCL is still valid because it only depends on your body anatomy plus the pedal and shoe heights.

Its also included a "Take Care" results section to protect your hamstrings from overstretch. The app will give you two scenarios, where the first one is the "Initial Setup" and the second is the "Final Setup". The idea behind this calc is to protect the legs from overstretch but at the same time to protect the knee from bending too much. The cyclist should set the "Initial Setup" and increase the seatpost length with time by small amounts until the "Final Setup" value is reached.

To find out your OCL, 8 parameters are necessary:

(1) Total Height with Shoes

(2) Total Height

(3) Seated Height

(4) Upper Legs Width (or HJCR Height)

(5) Knee Height

(6) Ankle Knuckle Height

(7) Ankle Knuckle to Ball Foot (or to Axis Pedal Center)

(8) Pedal Height (Flat or other type )

For the "Maximum Frame Size" and "SeatPost Length", 3 parameters are necessary:

(9) Saddle Minimum Height

(10) Saddle Position (back or fore)

(11) Seat Post Angle (0 to 90 degrees)

You can use this info to find your Optimum Crank Length because everyone's anatomy is different and using a standard crank length (170/175 mm) might not be the best option for you!

The default angle for maximum leg extension is 155 degrees, for minimum 70 degrees and for the ankle rotation 20 degrees. In the "Settings" you will be able to change those values according to your preferences.

You'll be able to save your own parameters, your friends or family, and edit or calculate it later on.

The parameters can be in mm (SI) or feet and inches (imperial) and must be defined in the "Settings".

If you want to test this app first on your device check out the FREE Version. The FREE version will show the calc results as zeros, but the functionality is the same.

Protect your knees and enjoy cycling more!