Originally Posted by Mr Sir

I personally use 125 mm cranks. I am short, 5''7 with short legs. I don't care what others say. while I used to only be able to do 10 miles a day comfortably I can now do 100. It completely changed cycling for me , elevating it to a higher level. For years I rode on cranks that were way too large (170mm) ignorantly and it did not do my knees any good. I did try 165, 150, 152 and 140 in the process. 125 feels perfect. If I ever find 130s and 135s I might try them. I rather ride with reduced torque than continue to bust my knees up. And I tried all fitting methods.
I know a very tall cyclist I highly respect (over 6'7) who swears by 145 mm cranks.