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I have a leg length difference of as much as 1cm due to a non-biking accident. Adding padding to my shoe doesn't help. A friend recommended that I get pedal stacks (and a longer bolt) to my SPD-style pedals (or any other clipless pedal) for my shorter leg. I know it will affect the rotation, but it's better than wobbling on my bike with uneven hips because of the 1cm difference. Any advice? And where can I buy a pedal stack or any other equipment, so that my leg muscles are as even as possible?

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Are you talking about adding the "stack" to the pedal, or to your shoe? I would think adding it to the shoe would make the most sense, and one could use a piece of Lexan or such for this duty, after a little work with saw, drill, and rasp. (I don't know how you could add the height to a standard SPD pedal.) – Daniel R Hicks May 21 '12 at 17:58
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(The other option is a shorter crank on that side.) – Daniel R Hicks May 21 '12 at 17:59
I think I might try Daniel's second comment. The "standard" road crank is 172.5mm, but you can get down to 165 and up to 175 which makes for a 10mm = 1cm difference. I think that what you would actually need is a 5mm difference as you get 5mm up and 5mm down as the pedals rotate giving you the 1cm. Regardless, I'd involve a good bike fitter. – Ken Hiatt May 21 '12 at 18:49
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I thought of posting a comment of a shorter crank on one side, but it doesn't seem like a good idea because it would be lower at the top (instead of higher, like it should be) and would lopside the pedaling effort. I would add to the shoe to stay more 'even' - but the key would really be what makes you most comfortable. – Ehryk May 22 '12 at 16:04
@DanielRHicks The gospel according to Sheldon (sheldonbrown.com/cranks.html) does not recommend mixing crank lengths. I think Ehyrk has a good point. – JamesBradbury Feb 20 at 12:52

1 Answer

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Be very careful about making leg length adjustments on your bike. There are several red flags about this. All of which you may be aware of or may not. 1st, a leg length difference is very difficult to diagnose, ecept with an experienced physio, or an X-Ray/MRI.

Most good physios will send you for an X-ray if they suspect a leg length difference is causing you an issue. 2nd, The body will naturally compensate for up to a 2cm leg length difference with pelvic tilt, and while that is less helpful on the bike, you don't automatically need to add stack height if you have a leg length difference.

And last, a 1cm difference in length does not mean a 1cm compensation, even if you do need to compensate. It is something that needs to be looked at professionally, and any compensation needs to be worked in slowly. Generally, adjustments in the 2mm range in one go are considered appropriate. More than that can(not always, but quite often) cause bigger issues than they solve.

Long story short, be careful what you do, go see a professional medical bike fitter, preferably a physio with extensive bike fitting experience, and follow their instructions. Oh, and be prepared to pay for the privilege, while realizing that it will take time to sort you out properly. There is no magic bullet fix here.

Look up the Boulder Center for Sports Medicine. They specialize in issues of exactly this type, and they designed most of the equipment to diagnose and correct them. Like the 3D bike fitting camera systems.

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Thanks everyone. The length was definitely professionally diagnosed, but as you say, I had never thought of pelvic tilt, which is involved in my case. I'll seek some professional fitter's advice. Thanks very much! – Stephanie May 23 '12 at 19:29
No problem. I don't want to discourage you, but it's easy to damage when you correct an issue like the one you have if you get it even a little wrong. – zenbike♦ May 24 '12 at 14:51
@Stephanie - If you're happy with this answer (which seems very helpful), I suggest clicking the Check Mark/Tick on the left to accept it and give the author recognition. – JamesBradbury Feb 20 at 12:44

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