Quote Originally Posted by Catriona View Post
I could be wrong - but I'm 5'1, use 165 mm crank arms, get knee pain with 170mm crank arms, and I usually have my saddle all the way back on the seat.
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Yes, that makes total sense. However, the OP isn't complaining about knee pain, so I'm not sure the crank length is the problem. Maybe the seat tube angle is part of it. Maybe she needs to adjust her reach shorter unlike my first guess, but I still think it's more likely a reach issue causing back and shoulder pain than a crank length problem. The cranks could be wrong for her build, but I don't think that's related much to the pain issue here.