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  #1  
Old 05-09-2022, 04:25 PM
ucdcrush ucdcrush is offline
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6mm of shims

Hi all. Just joined after being a long time reader.

I had a bike fit about 3 weeks ago. He said I didn’t have a structural leg length difference, but was dropping my left hip and not extending my left leg as much. (I think this was causing the right-sided knee pain I was having, which went along with an uneven feeling on my right pedal stroke). We ended up with 6mm of shim under my left cleat, after seeing I was still dropping my left hip with 3mm. He also gave me some pelvic stability exercises to do, stretches, and recommended unilateral leg exercises.

He wasn’t the most talkative guy but did mention that the exercises and the shim may improve things to where the shim could be decreased or eliminated.

So far, though I took last week off, I seem to notice that my pedaling feels smoother when I am concentrating on extending my left leg. But before the shim, and as I was riding soon after getting it, I’d notice that my left stroke felt very smooth and my right very uneven which I chalk up to me sliding over to the left side to protect that leg. (My stroke did feel smoother if I lowered my saddle 5mm, but that felt low to me). For what it's worth, I have a 83.5cm inseam and my saddle height is 73.6. It felt smooth at 73, but also felt too low.

I’m curious from those experienced with shimming, what will I as the rider notice over time if things are improving? Will the pedaling feel smoother? Will I eventually feel like my left leg isn’t extending as far (due to the shim) even with the smooth stroke (i.e., not simply that I’m still dropping my left hip which leads me to feel that lack of smoothness on the right)? And would that be the indicator for when the shim can be decreased/removed?
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Old 05-09-2022, 04:33 PM
robt57 robt57 is offline
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I think all you can really do is get a second Dr.'s opinion. Nutha fitters fit/opinion.

I think I'd use a shorter crank arm before I'd get to 6mm of shim. But not claiming anything but guessing...

Seems though I read process was to only correct 50-60% of such discrepancy, not 100%. Or to do it in steps if a lot, 3mm, then 1000 mile later the other 3mm or something along these lines.
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  #3  
Old 05-09-2022, 04:44 PM
tjk23 tjk23 is offline
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Quote:
Originally Posted by ucdcrush View Post
Hi all. Just joined after being a long time reader.

I had a bike fit about 3 weeks ago. He said I didn’t have a structural leg length difference, but was dropping my left hip and not extending my left leg as much. (I think this was causing the right-sided knee pain I was having, which went along with an uneven feeling on my right pedal stroke). We ended up with 6mm of shim under my left cleat, after seeing I was still dropping my left hip with 3mm. He also gave me some pelvic stability exercises to do, stretches, and recommended unilateral leg exercises.

He wasn’t the most talkative guy but did mention that the exercises and the shim may improve things to where the shim could be decreased or eliminated.

So far, though I took last week off, I seem to notice that my pedaling feels smoother when I am concentrating on extending my left leg. But before the shim, and as I was riding soon after getting it, I’d notice that my left stroke felt very smooth and my right very uneven which I chalk up to me sliding over to the left side to protect that leg. (My stroke did feel smoother if I lowered my saddle 5mm, but that felt low to me). For what it's worth, I have a 83.5cm inseam and my saddle height is 73.6. It felt smooth at 73, but also felt too low.

I’m curious from those experienced with shimming, what will I as the rider notice over time if things are improving? Will the pedaling feel smoother? Will I eventually feel like my left leg isn’t extending as far (due to the shim) even with the smooth stroke (i.e., not simply that I’m still dropping my left hip which leads me to feel that lack of smoothness on the right)? And would that be the indicator for when the shim can be decreased/removed?
If you are listing to one side, then your saddle is too high. I would drop the seat and forget the shims. A lowered seat is going to feel too low at first, probably because you have been overextending. Forget all the saddle height formulas and go with what feels right.
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Old 05-09-2022, 05:41 PM
ucdcrush ucdcrush is offline
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To add in.. when I went to the fitting session, I had my saddle at 73 and he raised me to 73.6 after watching my pedaling (from both sides). He didn't use any computerized measurement, nor inseam measurement, but went from observation.

I am reluctant to ditch the shims at this point, only because I've been unsuccessfully trying to fix my own fit for over a year as I'm riding more and riding harder. I've ridden at 73.6 even before the fit for a period of time, but had that uneven feeling and right knee pain (as well as the right knee brushing the top tube occasionally) which I am now chalking up to me leaning down to the left.

Also, in my non-riding life, I favor my left side which I think is due to the fact that I have a titanium gamma nail in my left femur to prevent an impending fracture. I've had that in there for over 10 years, and my left leg (and glute) is physically smaller and I'm sure weaker than my right. Not exactly sure how this would play into cycling, but I'm not surprised if it's factoring in.
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  #5  
Old 05-09-2022, 08:03 PM
fried bake fried bake is online now
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Here’s one method of measuring LLD

https://www.stevehoggbikefitting.com...h-differences/


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  #6  
Old 05-10-2022, 03:12 PM
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Ti Designs Ti Designs is offline
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If only it were that simple...

Your leg has this pivot called the knee which adds complexity. A leg length discrepancy just means there is a difference in length from foot to hip, it doesn't tell the whole story. On the bike the hip is a horizontal member, generating force by extending down from the hip. The tibea on the other hand is more along the lines of a connecting rod. Contracting the quad muscle extends from the knee, the resulting force is forward.

There are measuring devices that give a better picture of what's going on, but so few people understand what they're looking at that you'll never find anything written about them. They're called power meters (you may have heard of them), but you're going to need force vector information (which they don't want you to have). A good example would be the Pioneer power meter which shows force vectors every 30 degrees.

The bike is the hardest case for the body to adapt to. When walking your foot is free to go wherever it wants as soon as it leaves the ground, so you're self adjusting. The bike is the rare case where both feet have to follow the pedals around in the same circle. If there is a femur length difference your body is going to want to turn one circle forward of the other one. The resulting force vectors can be seen with a power meter that shows that data, it also has a tendency of creating a pain over the iliac ridge on the longer side, because those muscles never come out of tension. The solution for this is a fore/aft adjustment of the cleats, not a shim.

Here's the real problem - there are too many variables. You weren't made in a factory with high tolerances. Any two parts of your body could be significantly different, nothing says your hips are straight or your SI joints are level. Your long bones weren't in communication with each other as you were growing... The best you can hope to do is understand each factor on it's own, then try to grasp how it all fits together.

One final piece to this puzzle - reflexes. If you were just a skeleton on a bike it wouldn't be so bad. Your body has all kinds of reflexes, which in theory are there to protect the body. The problem is there's nothing keeping the reflexes from injuring the body (which is what almost all cycling related injuries are). I've studied the differences between muscle contraction and a pull reflex (the muscle's response to raped extension). muscle contraction is limited by a spiral recruitment of muscle fibers. A pull reflex has no such restrictions.
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Last edited by Ti Designs; 05-11-2022 at 12:47 PM.
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  #7  
Old 05-11-2022, 10:46 AM
ucdcrush ucdcrush is offline
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It's interesting to see the replies. I have seen the youtube videos where Cam Nichols was fit by Neil Stanbury, and to help Cam from dropping his right hip, put 6mm of shim under his right shoe. I also see on his more recent videos where Neil is fitting an ultra long distance cyclist, and had shimmed him as well as put something taped to his saddle to remind him if he's listing to one side. And I think in that case, the shims are decreased or eliminated now.

I figured that is similar to what my fitter is trying to do with me. But have also read some people are against shimming (maybe unless there's an anatomic leg length difference). I would prefer to work on my body to make it more symmetrical if the shim is a bandaid that is going to slow down that progress. But given that it's something used by respected fitters like Neil Stanbury, and again that I've been trying to get my own fit right for a while, that's why I'm open to using it in addition to really working on the off the bike exercises and stretches that my fitter recommended.

It does seem though that lowering the saddle wouldn't always be the automatic best answer when one is dropping one hip.. because that leg might actually be shorter, or at least be acting shorter, and lowering it might make it lower than optimal for the longer (or acting longer) leg.
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Old 05-12-2022, 10:34 AM
yinzerniner yinzerniner is offline
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Quote:
Originally Posted by ucdcrush View Post
It's interesting to see the replies. I have seen the youtube videos where Cam Nichols was fit by Neil Stanbury, and to help Cam from dropping his right hip, put 6mm of shim under his right shoe. I also see on his more recent videos where Neil is fitting an ultra long distance cyclist, and had shimmed him as well as put something taped to his saddle to remind him if he's listing to one side. And I think in that case, the shims are decreased or eliminated now.

I figured that is similar to what my fitter is trying to do with me. But have also read some people are against shimming (maybe unless there's an anatomic leg length difference). I would prefer to work on my body to make it more symmetrical if the shim is a bandaid that is going to slow down that progress. But given that it's something used by respected fitters like Neil Stanbury, and again that I've been trying to get my own fit right for a while, that's why I'm open to using it in addition to really working on the off the bike exercises and stretches that my fitter recommended.

It does seem though that lowering the saddle wouldn't always be the automatic best answer when one is dropping one hip.. because that leg might actually be shorter, or at least be acting shorter, and lowering it might make it lower than optimal for the longer (or acting longer) leg.
Was going to suggest that video, and glad you found it. If you respect and trust your fitter I would say go with the shimming to see how it works.

As you can see from the vid the body is very adaptable, but sometimes it can lead to unwanted/suboptimal adaptations. The shimming is pretty extreme but if you feel better then that's all that counts.
Good luck and keep us abreast of the progress.
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Old 05-12-2022, 04:57 PM
tjk23 tjk23 is offline
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Quote:
Originally Posted by ucdcrush View Post
It's interesting to see the replies. I have seen the youtube videos where Cam Nichols was fit by Neil Stanbury, and to help Cam from dropping his right hip, put 6mm of shim under his right shoe. I also see on his more recent videos where Neil is fitting an ultra long distance cyclist, and had shimmed him as well as put something taped to his saddle to remind him if he's listing to one side. And I think in that case, the shims are decreased or eliminated now.

I figured that is similar to what my fitter is trying to do with me. But have also read some people are against shimming (maybe unless there's an anatomic leg length difference). I would prefer to work on my body to make it more symmetrical if the shim is a bandaid that is going to slow down that progress. But given that it's something used by respected fitters like Neil Stanbury, and again that I've been trying to get my own fit right for a while, that's why I'm open to using it in addition to really working on the off the bike exercises and stretches that my fitter recommended.

It does seem though that lowering the saddle wouldn't always be the automatic best answer when one is dropping one hip.. because that leg might actually be shorter, or at least be acting shorter, and lowering it might make it lower than optimal for the longer (or acting longer) leg.
Look up Bikefit Tuesdays on Youtube.
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Old 05-12-2022, 06:59 PM
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Ti Designs Ti Designs is offline
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Quote:
Originally Posted by ucdcrush View Post
It's interesting to see the replies. I have seen the youtube videos where Cam Nichols was fit by Neil Stanbury, and to help Cam from dropping his right hip, put 6mm of shim under his right shoe. I also see on his more recent videos where Neil is fitting an ultra long distance cyclist, and had shimmed him as well as put something taped to his saddle to remind him if he's listing to one side. And I think in that case, the shims are decreased or eliminated now.
While I spend most of my time teaching pedaling technique, you're never going to unlearn a leg length discrepancy. Learned behavior is one of the hardest things to deal with as a fitter because it often doesn't make any sense. I had a guy in my winter pedal stroke class a few years ago who I called a half million miles of bad habits. I could guess most of his injury history just based on his learned adaptations.
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  #11  
Old 05-13-2022, 09:16 AM
benb benb is offline
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6mm seems huge for a non-structural discrepancy.

How did this guy decide you had that big of a discrepancy anyway, and how did he decide you have a functional and not structural one? Chances are anything he was able to do in a bike shop/fit-lab can't possibly be accurate.

I have a femur/foot thing going on. It is theoretically possible to do some of the correction with shims but shims are/were really really hard to deal with when I tried them. They interfere with cleats and cause all kinds of other issues. You really don't want to use them unless you absolutely have to. For me they really didn't do anything useful anyway. Leave shims to people who have serious structural issues.

It does very much sound like it may be a case of recommended saddle height being too high. In my own experience I have really noticed a lot of these fitters who follow a system have a tendency to try and recommend the absolute maximum seat height they can and ignore tendencies to drop your heels when pedaling hard and that will exacerbate all of these issues to a great extent. The ones who watch from experience won't try for the highest saddle height right away.

Unless patellar tendonitis becomes an issue in the long leg if you set your saddle up for the shorter leg the longer leg can just bend more to take up the slack. I had patellar tendonitis when I first started cycling because I self fit myself and I think any untrained person will set themselves up low to bias against all these issues. IME the range of saddle height between low saddle issues and high-saddle/leg/hip issues is pretty large... like 4cm or more. So if the fitter is recommending a sky high saddle height that causes issues there's going to be plenty of room to lower the saddle height and lose things like shims.

I get/have illiac issues on my short side (partly caused by a fall though).. I would love to hear more about Ti's theory on that happening on the long side. For me I think if my cleats are not offset enough my long side pushes that sitbone backwards which rotates my hip and causes my right sitbone to fall of the saddle. I then constantly try and use some of the lateral hip muscles to fight this. Almost no one who has ever fit me has been able to see this. I can almost always just trial and error into a good cleat position to prevent it, but it's really hard to repeatedly figure out what that offset should be without taking everything else into consideration and it makes getting new shoes really obnoxious. The most effective thing with the illiac/lateral thing for me has been exercises... cycling and running don't do much to increase that lateral strength.

I would never even know anything was going on at all if it wasn't for cycling. I suspect if I got X-rays that my right femur is longer but my total leg length is almost exactly the same because the left leg is longer in the shin and/or my right foot doesn't pronate as much. Somebody who has a really really good eye might notice something if watching me do squats, but not really with walking/running.

Last edited by benb; 05-13-2022 at 09:21 AM.
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Old 05-13-2022, 05:45 PM
ucdcrush ucdcrush is offline
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Quote:
Originally Posted by benb View Post
6mm seems huge for a non-structural discrepancy.

How did this guy decide you had that big of a discrepancy anyway, and how did he decide you have a functional and not structural one? Chances are anything he was able to do in a bike shop/fit-lab can't possibly be accurate.
He watched me pedaling under load from all sides, and saw that I was dropping my left hip. Tried 3mm, still dropping left hip, added another 3mm. I didn't explicitly ask him whether at 6mm I now wasn't dropping my hip, I just know he decided to stop at 6mm and told me to go ride on that for a while and let him know how it was. He also pulled my shoes off a few times to adjust cleat location and rotation.

He did a physical exam. I don't think he was claiming that he knew my legs were identical length. Just that no physical difference jumped out at him when I was laying on the table. Maybe for some people he can quickly see that their legs are actually of different lengths. And probably no one has perfectly symmetrical leg, but I'm guessing a difference that isn't noticeable probably won't be something making or breaking a bike fit.

As I mentioned above, given that way I favor my left side (with the titanium nail in my hip), I am not surprised that I pedal differently on that side. I've also heard that we tend to "protect" our dominant side, which in that case is my left side as well. Also, I've tried to self-fit for quite a while now, while not doing any flexibility or strength work off the bike. I'm hoping with the shim and all the stretching and unilateral leg work I'm doing now, that I'll see an improvement.

I started the thread though to ask others who have used shims, what experience they had to know that they could try decreasing or removing the shim. I'm still wondering about that. But I believe one thing could be that I am able to ride at the saddle height he put me at while feeling that my right leg (where I've had knee issues) is nice and smooth. That's assuming that the un-smoothness I've experienced there is because I'm dropping my left side down. So could be that once I have a nice smooth right side stroke, I can take one of the 3mm shims out and get my left leg used to extending that extra bit to where I'm not dropping it and messing up the right side stroke.
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Old 05-16-2022, 09:19 AM
benb benb is offline
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He may have nailed it.. personally I'd want to get on one of those setups that graphs power through the pedal stroke and can be used to check to see that both legs are working well and the stroke isn't too asymmetric. I've done that with both setups.

Because we sit behind the BB our leg is basically diagonal at the bottom of the pedal stroke. A shim is theoretically a vertical adjustment and sliding the cleats fore/aft is theoretically a horizontal adjustment. But if you drop the heel or point the toes both of them end up turning into diagonal adjustments.

Ti Designs is always talking about how if you try and force a joint to go beyond its happy range the muscles will tighten to try and protect the joint. Once you're really aware of that it's very easy to feel it happening. Since the leg is diagonal at the bottom of the pedal stroke when your "hip drops" it's really the leg pulling that sitbone both forward and down. For me what I'll really also notice when this is happening is the thigh on the right (long) leg starts to rub annoyingly on the saddle nose as well.

It's why you can start a ride with the saddle too high or too far back for the shorter leg to benefit the longer one and tolerate it at first if you're fresh and limber... maybe you point the toe on that short leg to compensate. Then you start getting tired and the calf can't handle pointing the toe. Then the hamstring starts tightening up and pulling on your hip and it all starts feeling worse and worse.

It's not that you should second guess the fitter and do it yourself, but maybe get a 2nd opinion and more information. The shim tends to just have a lot of practical annoyances.. unless the shim clearly results in big power & comfort gains over all the other ways to compensate its hard to say it's worth it.
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Old 05-16-2022, 08:57 PM
ridethecliche ridethecliche is offline
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Sounds like the fit had helped.

I'd likely suspend disbelief for a minute and try it out for a month or so. If you don't have any issues, see where that gets you.

I also really recommend that cyclists get into doing yoga because the fact that we sit most of the day and also on the bike means our hamstrings get extremely tight. People compensate for that loss of flexibility with their lower back which is sub optimal.

Ymmv.
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