How long should your MTB cranks be?

Optimal crank length is proportional to leg length, which is generally proportional to height. Exceptions abound, but this logic — smaller people need smaller bike parts — is sound.

The height difference between 5’0″ and 6’8″ (a full size run) is 33%.

The length difference between 165 and 175mm cranks (the broadest common range on stock adult MTBs) is 6%.

If you’re shorter than the stock range, you’ll benefit greatly from shorter cranks. If you’re taller, run what came on your bike; there are handling advantages to running shorter than Zinn’s number.

What do y’all think?