# Crank Lengths...



## Geezer (Feb 5, 2004)

I recently put a new bottom bracket and crank on my bike. While going over the options my LBS mechanic/shop owner asked if I ever thiught about using 2 different length cranks. 

The reason he was asking has to do with my leg lengths. My left leg is 1.25 inches longer than my right. He thought that it might help me with my power/cadence/rythm.

I thought (at the time) that it was a valid consideration but when I discussed it with my doctor he became concerned with my lower back. He said that changing after riding and compensating for as long as I have may throw my back out.

Any similar experiences or thoughts?


----------



## perttime (Jun 27, 2005)

Sheldon Brown didn't think mixing lengths is a good idea.
Also: do you feel unbalanced, spinning "normal" cranks?

_"When one leg is significantly shorter than another, the shorter leg is also usually weaker than the longer one. Since a short crank results in a higher gain ratio, this setup would ask the the weaker leg to push harder than the stronger one.

A better way to deal with significant leg-length discrepancies is to build up the sole of the shoe, or to use longer bolts and spacer washers between the cleat and the shoe sole, or to build up the pedal by some sort of add on attachment."_
http://sheldonbrown.com/cranks.html


----------



## Geezer (Feb 5, 2004)

*Crank Lengths*

Between my LBS guy, my doctor and myself, we arrived at a similar conclusion as the Sheldon Brown philosophy. However I don't think that I will build anything up since I don't have any problems (yet) due to the difference in lengths. I think that I am fishing for ideas in case I develope knee or back problems in the future. 

The conclusion is correct that one leg is weaker than the other and at this time I don't struggle with forcing the weaker leg to use more power. It seems to be maxxed out whereas the stronger leg continues to gain strength and power.

Thanks


----------



## Creakyknees (Sep 21, 2003)

Geezer, you should read the back articles / topics on "fit" here:
http://www.cyclingnews.com/fitness/
I think they've covered this topic here and there.

Also check out Steve Hogg's website, and maybe get in touch with him.
http://www.cyclefitcentre.com/


----------



## ctoestreich (Aug 14, 2008)

Geezer said:


> I recently put a new bottom bracket and crank on my bike. While going over the options my LBS mechanic/shop owner asked if I ever thiught about using 2 different length cranks.
> 
> The reason he was asking has to do with my leg lengths. My left leg is 1.25 inches longer than my right. He thought that it might help me with my power/cadence/rythm.
> 
> ...


My legs are not equal length either. That is what they make shims for. I have my cleat on one side about 1/2" higher than the other. Not sure of you can easily overcome the 1.25 inch gap, but seeing what your LBS/fitter can do in the way of shims might bring it closer to even. You could also add shims slowly over time to help ease into the new stride.


----------



## j-dogg (Feb 19, 2009)

okay now here is something for you

I'm low cadence high torque. even length.

Do I spring for the 180mm crank?


----------



## Ibashii (Oct 23, 2002)

Geezer said:


> I recently put a new bottom bracket and crank on my bike. While going over the options my LBS mechanic/shop owner asked if I ever thiught about using 2 different length cranks.
> 
> The reason he was asking has to do with my leg lengths. My left leg is 1.25 inches longer than my right. He thought that it might help me with my power/cadence/rythm.
> 
> ...


I've been through this in several sports for many years...a couple of thoughts:

1) have you looked closely at the actual numbers in your leg-length discrepancy? It makes a difference if your actual bone length difference (femur +tibia) is noticeably less than your overall leg-length difference. You've probably done this, but just to make sure...in my case, the C/T scan came up with a LL difference of 8 mm, but the bone length difference is only 2 mm! That means the other 6 mm are made up in either soft tissue differences or internal misalignment (SI joint and other weird suspension-like stuff in the hips, tissue in the knees, etc.), which are things that can change with time...bone length, however, is rather permanent.

2) Pretty much everyone I've talked to or read agrees that it's suicide to try and correct 100% of a leg-length difference after two or more decades of internal compensation: I've never heard anyone suggest more than 75%, and many say half at the most.

3) Some people say you should NEVER attempt to make this compensation until you have tried everything else (different types of PT, massage, strength exercises, chiro, etc...). I don't agree with this, but lots of very clever and well educated people do so it's worth mentioning.

4) Although I've had mismatched cranks suggested to me by other riders, I've never met a single sports medicine professional who thought it was a good idea. Not one. IMO it's a very expensive bad idea for reasons mentioned above and others.

5) 1.25 inches is enormous, even if it's not all bone-length. Do you correct for it in your daily footwear? If not and if you do start shimming, you have to do it SUPER gradually, no more than 2 mm at a time, and put in a good quantity of miles at each stage. I don't want to say a number 'cuz I'm no health professional, but doing it too quickly can really be problematic.

IME, a slight correction of my 8 mm LL difference (about 2 mm) makes the difference between me being able to ride without worrying about it all the time and me being constantly bothered by ITBS in the short leg. Through a combination of insoles and shims I've experimented one mm at a time (which is a major PITA) and finally found a combination that works.

Then again, my competitive running career was cut drastically short by ITBS, and no amount of PT or shimming got me over the hump. That's why I bought a road bike.

Hope that helps and let us know what you find out and end up doing; I've always my ear to the rail on this one, 'cuz it can really menace my riding, and thus my mental health.


----------

