Uneven cranks!

[mr messy]

Would using different length cranks be a viable option to accommodate a knee injury(restricted movement range, unable to fully extend or bend) or am i barking up the wrong tree?

Cheers

Messy

 

[gaz]

You are much better off putting a shim under the shoe / on the pedal than using uneven cranks.

Crank length affects leverage and effectively changes the gear ratio, which means the leg that is pushing the shorter crank is actually doing more work.

 

[mr messy]

Cheers Gaz

Completely forgot the whole levers premise.
And to think Archimedes is one of my favourite old greek dudes.....

Unfortunately a "shim" would make things worse when pedal at its highest.

Trying to find a compromise short of a new knee lol

 

[Theseus]

A number of years ago, before I did my own maintenance, I took my bike in for some work that required the mechanics to remove the pedals. The left pedal was quite stuck and in the process they managed to strip the thread to the extent that it was not possible to re-tap. The only spare left crank they had was longer than the right one and as I needed the bike I agreed to them fitting this until they could get a replacement. At which point they were to call me and we would swap.

I never did get the call and for at least a year rode with the left crank 5mm longer than the right. It felt a bit strange to start with, but after a while I got use to it. Going back to cranks the same length gave a similar feeling of oddness for a while as my body re-adapted back.

 

[MrHappyCyclist]

Crank length affects leverage and effectively changes the gear ratio, which means the leg that is pushing the shorter crank is actually doing more work.

Or just making a smaller contribution, perhaps.

 

[MrHappyCyclist]

I have thought about this myself as I have some restriction in movement of my left leg. It's still OK at the moment, but will get worse, so the shorter crank on that side might be the answer when I get to that stage.

The following site mentions this as a solution:
http://www.lightfoot...com/special.htm ("Asymmetric crank lengths for persons with a short leg or restricted knee movement")

I do agree with Gaz that the answer for a shorter leg is to extend the leg rather than change the crank length. For restricted movement, though, it is worth a try.