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Conference noted::bicycle

Title: Bicycling
Notice:Bicycling for Fun
Moderator:JAMIN::WASSER
Created:Mon Apr 14 1986
Last Modified:Fri Jun 06 1997
Last Successful Update:Fri Jun 06 1997
Number of topics:3214
Total number of notes:31946

588.0. "Unequal Leg Lenghts" by RETORT::SCHNARE (CHARLIE SCHNARE) Fri Mar 25 1988 15:24

    A friend of mine has a problem with unequal leg lenght, 1.75" to
    be specific. How can his bike be set up to best compensate for this? 
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588.1Build up the pedal on the short sideUMBIKE::KLASMANMon Mar 28 1988 10:2611
< Note 588.0 by RETORT::SCHNARE "CHARLIE SCHNARE" >
                            -< Unequal Leg Lenghts >-

I would think that the best way to compensate for this would be similar to the 
way in which it is compensated for walking...build up the shorter leg to match 
the longer one.  For biking, I'd set the seat height for the longer leg, then 
build up the pedal (in this case, add a 1.75" block) for the short leg.

I'm sure I've heard of this for smaller differences.  Don't know if such a 
large difference would cause a problem.

588.2MOSAIC::WASSERJohn A. WasserMon Mar 28 1988 15:148
RE: Unequal Leg Lengths

> Build up the pedal on the short side.

	Another possibility: Different length crank arms.  A shorter arm
	on the short-leg side would not only raise the bottom of the
	short legs cycle but would also reduce the total amount of
	motion of the short leg.
588.3How accurate ? how precise ?MENTOR::REGKeep left, except when not passingTue Mar 29 1988 12:1922
    
    	Well, the right answer is probably a combination of smaller
    circle via a shorter crank and getting that circle's centre closer
    to the saddle via some kind of pedal blocks.  As I remember .0,
    it was about a 1 3/4 inch difference; unless the person has one
    leg that's right on the edge of being either too long or too short
    for a 170mm crank it shouldn't be necessary to use unequal crank
    arms, however theoretically correct that might seem.  There must
    be millions of people riding around on 170mm cranks with leg lengths
    ranging from very short to very long, I doubt that many of them
    ever bother to go to longer or shorter cranks.  Blocks seem the
    simplest solution for  "close enough".
	I have bikes with 165mm (quasi track bike) to 175mm (ATB pretender), 
    and a couple in between, it doesn't make THAT much difference in
    practice.  (Well, the short ones do help to keep the pedals from
    digging into the black top on sweeping curves...)
    

            	Reg
         
    	{I could do the geometry (honest I could) but it wouldn't come
    out on a terminal.}