Cries on hills
Join Date: Jun 2007
Location: Central NH
Bikes: 2007 Trek Pilot 1.2, 1969 Raleigh Sprite 5
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Crank arm length
Trying to think something through.
I haven't been comfortable on my wife's mountain bike; it's frame is a bit too small, which is a good though for an MTB; but I've always felt like my knees are going into my chest if I set it where I don't over extend at full leg extension.
Now, I have my road bike fitted to me, all feels good; but as a roadie I'm used to spinning--and this MTB feels wrong. Long gentle climbs just feel awful to take seated. I'm starting to wonder if it's due to the crank arm length. I don't have my road bike in front of me but I think it has 170mm cranks while the MTB has 175's. So I'm wondering, would it make sense to drop the MTB down to 170's or maybe even 165's?
In my head, at full leg extension, the saddle needs to be in the same spot regardless of crankarm length; and dropping crankarm length means the saddle has to go upwards. Which seems wrong, for mount/dismount. But at the same time, at the top of the stroke my knee won't be so high, which might fix the problem I'm having.
In the same vein, does foot position matter in this? I ride clipless on road, which puts pedal axle under the ball of my toes. MTB, I use platforms and ride with the pedal under my arch. I think, I don't really pay attention to exact location, but definitely farther back. My old 3 speed I think has 165mm cranks, platforms, and no problems with pedaling.