The above posts all very interesting.
Most of the studies (probably not actually that scientific) that have been done basically come to a conclusion that almost everyone would benefit from going shorter. Clearly not the case and any formulas to calculate crank length have to be nonsense anyway.
Seems that short cranks work for riders with physiological problems whereas riders without any issues, like myself, need to find the middle ground. Yeah, I span more with the shorter cranks but did it benefit me? Don't think so. Feel better pushing a lower cadence.
This year i have tried, 172.5, 175 and 177.5mm cranks.
I'm 1m90 and saddle height 81.5cm
I felt a difference with al the cranks.
- With 177.5mm a had got more power but also knee pain
- With 172.5 mm more cadence but i felt like I could not push the power that I wanted
- 175 cranks best of two worlds
Pretty much what I experienced but with smaller size cranks!
What you've described is my experience too. The correct crank length for you is the one that is the best balance of each of those attributes. I think it has a lot to do with hip restriction. How deep into hip flexion you have to go. Also play a little with your saddle angle. The tilt of your pelvis will also have an effect on hip restriction.
I use a specialized Power which allows good tilt of the pelvis. saddle angle is very very slightly nose down but that's how these saddles are. If I feel like it needs tilting too much then it's a little too high. My hip angle is now more restricted with the 170's but it feels better, weirdly!