Originally Posted by
79pmooney
I started on 170s never thinking about it. Bought a race bike with 175s mid season. Everything about that bike felt right. All my ride times dropped radically and continued to do so the rest of the season. Had a major crash that fall. Started my next season on my beater fix gear with its short cranks. 3 days before my first late winter race I rode a long ride on the race bike. Mistake! My knees hurt after. Started a now 45 year journey of chrondomalcia patellae. And now had knees that really didn't like crank length change. On shorter cranks I feel the higher loads and my knees not liking it at all. 172.5 are just OK but not as good as 175s. 170s are playing games with keeping my knees happy enough to function. (Like "how many rides before I gotta get those replacements?")
So I keep it really simple. All my bikes including my 3 fix gears that get over half my miles are 175s. It works.
This is good. The thing with crank length is that it depends on the individule. When I was racing, I kept going slower. I was diagnosed with chrondomalcia patellae, similar to you. I ended up quiting racing and even cycling. Then decades later took it up again, but if I went too long the knee pain (and effects) came back. I went to 165 cranks to reduce knee flexion and I can ride longer without problems. If you don't have problems. Keep doing what your doing.
As some of these references above and Neill Tanbury, bike fitter, point out, it depends.
The good thing for both of us, and it should be a lesson for anyone that is dealing with issues related to pedaling is, try different length cranks and cadances. You may find something that works for you and enjoy riding again.
By the way, Matt Appleman, referenced above, is a taller guy, however because of an injury, rides shorter than 170mm cranks.