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longer crank for a slightly shorter leg?(3 posts)

longer crank for a slightly shorter leg?titansprodigal
Apr 30, 2003 1:37 PM
Im using a shim now but have heard of riders using a longer crank on the short leg. Which is better? Wouldnt a longer crank have a longer reach on the down stroke??
Nope, shorter crank on the shorter leg.jw25
May 1, 2003 8:34 AM
Seems counter-intuitive, but think about it for a second:
The short leg can't reach as far when fully extended, so using a longer crankarm on that side would double the imbalance. A shorter crank, though, will work similarly to a shim.
Actually, shims would promote an oval pedal stroke, since the pedal rotates the opposite direction of the cranks. So, at 12 o'clock, you've got the cranks' length plus the shim, but at 3 o'clock, you've just got the crank, since the cleat's still in the same position on the shoe. Okay, okay, there's some trig you could use to show the true effect, but for our purposes, this'll do.
In reality, I'd say shims will take care of most leg-length imbalances, if they're large enough to cause problems. Most people aren't symmetric, in the first place. For a large discrepancy, the crankarm swap might be more biomechanically sound.
Nope, shorter crank on the shorter leg.titansprodigal
May 1, 2003 8:49 AM
great reply, thanks alot!