Crank Arm

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jasonmccullum

Über Member
My left leg is 1 inch shorter than my right leg. Do you think it would be sensible to change the left crank arm to one that is 1 inch shorter than the right one.

If this was done then the effective turning circle would be the same for both legs.........i think
 

Archie_tect

De Skieven Architek... aka Penfold + Horace
Location
Northumberland
Possibly not because your left leg would be travelling a lesser distance than you're right which will set up an awkward imbalance at speed? ....would be worth checking at your local bike shop first.
 
OP
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jasonmccullum

jasonmccullum

Über Member
yeah i have special shoes already, but they are a pain with the pedal clips, and i can imagine that it would be harder with spd's
 

alecstilleyedye

nothing in moderation
Moderator
jasonmccullum said:
yeah i have special shoes already, but they are a pain with the pedal clips, and i can imagine that it would be harder with spd's

actually, if you can fit a clipless pedal system to your special shoes, that would be the best solution imo. clipless pedal systems are much easier to get on with that toe clips, especially if your special shoes are slightly 'taller' than standard.
 

andrew_s

Legendary Member
Location
Gloucester
I have seen odd cranks recommended as an alternative to built up shoes or pedal. I think it was recommended that the cranks differ by half the difference in leg length
 
jasonmccullum said:
My left leg is 1 inch shorter than my right leg. Do you think it would be sensible to change the left crank arm to one that is 1 inch shorter than the right one.

If this was done then the effective turning circle would be the same for both legs.........i think

For this to work you would need a left crank one inch longer, not shorter otherwise your problem would be worsened. For leg length plus crank length to equal the same each side, any shortness of the leg could be made up by a longer crank on the same side. I see no reason at all why this should not work.
 
Perfect Virgo said:
For this to work you would need a left crank one inch longer, not shorter otherwise your problem would be worsened. For leg length plus crank length to equal the same each side, any shortness of the leg could be made up by a longer crank on the same side. I see no reason at all why this should not work.

Eh, If his left leg is 1" shorter, then he wants the crank arm to be 1" less at the bottom of the swing so he can put the power down right to the bottom of the stroke. If his left foot loses connection with the pedal before the crank arm swings through the bottom of its rotation, then he will lose a load of efficiency as well as balance - or lower his saddle, and lose efficiency through not being able to extend his right leg.

I guess you have already tried to compromise by lowering your saddle half an inch from optimum and split the difference Jason ?
 

Mr Pig

New Member
I have a spare aluminium left crank knocking about here, a square taper one, I think it's 175 but I'd have to check. You're welcome to it if you want to try out the idea?
 

MartinC

Über Member
Location
Cheltenham
Using different length cranks is an pretty normal method of coping with different leg lengths. Eveyone's legs are different lengths so to some extent everyone is accommodating some difference anyway - but 1" is quite a difference. Your pelvis will have a tilt that it's grown to fit when you're standing or walking.

If you change the crank length you'll need to find a new saddle height that's a working compromise for both legs. Building up the pedal avoids this problem (by effectively raising the BB height for this leg).

The best approach is probably a combination of all 3. Crank lengths that differ by 5 or 10mm or so, a built up pedal or shoe and let your legs accomodate some of the difference.
 
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