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Leg Length and Left/Right Unequal Power Meter Balance

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Leg Length and Left/Right Unequal Power Meter Balance

Old 09-03-22, 10:29 PM
  #26  
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All,

Since we last talked, here's what I've done. I used one of these cleat risers on my right foot.

https://www.amazon.com/dp/B00BP52Y4Y...roduct_details

I went on four rides totaling over 75 miles.

1) August 22, 2022
17 miles, rolling hills and flats
Left/Right Power Balance = 54/46

2) August 24, 2022
17 miles, rolling hills and flats
L/R = 54/46

3) August 27, 2022
21 miles, a few more rolling hills and flats
L/R = 55/45

4) August 31, 2022
On this ride, I removed the cleat riser from my right foot
21 miles, a few more rolling hills and flats
L/R = 55/45

I've come to 2 conclusions

1) Focusing on L//R power balance doesn't matter for an amateur.
2) The Shimano dual-sided Dura Ace crank power meters are inherently inaccurate on L/R balance and total power output (lower) when compared to other meters. They are consistent within themselves, however. Shimano knows this but won't admit it. Interestingly, the drive side strain sensor is located closer to the bottom bracket than is the non-drive side strain sensor. You would think the L/R imbalance could be compensated for through firmware.

I base conclusion 1 one some of the posts above and conclusion 2 based on some research I've done such as

From DC RainMaker and Bike Radar
https://www.dcrainmaker.com/2018/04/...th-review.html
https://www.bikeradar.com/reviews/tr...-meter-review/
https://www.dcrainmaker.com/2022/05/...g-metrics.html

From Shane Miller GPLama

Hopefully this has been of some help to others. Thank you all for your input.

Glenn Atkins


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Old 09-13-22, 07:22 AM
  #27  
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the answer to this seems glaringly simple to me. drive side is on the right. your right leg will obviously have an easier time putting down power as a result. your left leg will have to compensate for this by putting out more power to match. mystery solved.
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Old 09-13-22, 07:35 AM
  #28  
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Originally Posted by Moisture View Post
the answer to this seems glaringly simple to me. drive side is on the right. your right leg will obviously have an easier time putting down power as a result. your left leg will have to compensate for this by putting out more power to match. mystery solved.
My left/right balance is in the range of 55/45, thus I need to put out more power in my right leg, not the left, to make it ~ 50/50.

Did you read my post #26 right above yours? A glaringly simple mystery already solved.

Regards
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Old 09-13-22, 07:52 AM
  #29  
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Glenn, how would I find out if one leg is longer than the other? Is there a test for that? My L/R is something like 45-48 on the left and as high as 55 on the right.
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Old 09-13-22, 09:18 AM
  #30  
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Originally Posted by GhostRider62 View Post
Glenn, how would I find out if one leg is longer than the other? Is there a test for that? My L/R is something like 45-48 on the left and as high as 55 on the right.
I had a bike fit at Retul in Boulder a couple of years ago and they didn't mention that I had a discrepancy. I forget exactly how they measured it.

I got it in my head that I may have a leg length difference when I consistently noticed my left/right power imbalance. It took a concentrated pedaling effort, which felt unnatural, to even out the power balance. I put a cleat riser (not an angled shim) under my right cleat and had no change so I took it out.

I did some research and considered the posts above and came to the realization that the L/R balance doesn't matter for an amateur and that Shimano is aware, and has been for a while, about the balance issue in their crank-based, two-sided meters.

A confounding factor for me was that I have always had left, outside toe numbness and hot-foot. But never in my right toes/foot - only the left. I also have peripheral neuropathy in both lower legs, not diabetes related. I thus began a journey to see if I could fix the numbness and hot foot.

1) had the bike fit, including custom Specialized insoles (done in 2020)
2) shimmed my left cleat (done in 2020)
a) i use one glove size above my normal. for example i use extra large instead of large
b) i use one shoe size above my normal size
3) more recently shimmed my right cleat (2022)
4) tried and then removed my right cleat riser (again, not a angled shim) (2022)
5) moved both cleats to the rear as far as I could (2022)
6) just within the last week went from a 138mm saddle to a 155mm to a 165mm saddle (2022)
7) just within the last week moved my seat forward 15mm, yes I know that's a lot even though it's only about 6/10 of an inch, but I'm relatively older and don't yet have enough flexibility (2022). I've been off the bike for a year - some from laziness but almost six months due to a severe right calf injury unrelated to cycling

I may raise my saddle some to compensate for its move forward, just don't yet know how much to move it.

What clearly helped the most with outer toe numbness and hot foot in my left foot was moving the cleats completely to the rear. Second best was shimming the left cleat and the bike fit. That's where the left shim came from. The fit mostly took weight off my hands.

I did 18 miles last night with all the above in place. Problems largely resolved even though it's a sample size of one.

Next on the list of things to try if the above don't continue to work include:

https://mid-foot-cycling.com/
https://www.g8performance.com/insole...ievers-bundle/

I do not have any affiliation to any product mentioned in this post.

Glenn

Last edited by GAtkins; 09-13-22 at 09:25 AM. Reason: Edited to correct metric measurement in item 7 from 150mm to 15mm
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Old 09-13-22, 09:57 AM
  #31  
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Originally Posted by Polaris OBark View Post
Why is the idea of using a shorter crank arm for the shorter leg frowned upon (vs a shim)?

The problem I had when I tried a shim was that the stack height really made it hard to tolerate, whereas the shorter leg only bothers me if the saddle is at the high/optimum for the longer leg. (This difference is small enough that I didn't notice it existed until my bike fitter/framebuilder mentioned it to me, but I can feel one leg can be over-extended when the other is comfortable.)
The gist of it is work=force x distance. This means that the leg attached to shorter crank arm will be doing a different amount of work than a leg attached to a longer crank arm.

Ideally, you'd want both legs to be doing the same amount of work. Generally the way to do this, is to align the work to where the rider happens to be. I.e., a shim.

Though there is a bunch of different ways one limb can be different than the other. So, there are undoubtedly cases where a different crank arm length could be appropriate. But, that would between that person & their licensed doctor professional based on that persons particulars.
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Old 09-13-22, 10:31 AM
  #32  
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Originally Posted by GAtkins View Post
I had a bike fit at Retul in Boulder a couple of years ago and they didn't mention that I had a discrepancy. I forget exactly how they measured it.

I got it in my head that I may have a leg length difference when I consistently noticed my left/right power imbalance. It took a concentrated pedaling effort, which felt unnatural, to even out the power balance. I put a cleat riser (not an angled shim) under my right cleat and had no change so I took it out.

I did some research and considered the posts above and came to the realization that the L/R balance doesn't matter for an amateur and that Shimano is aware, and has been for a while, about the balance issue in their crank-based, two-sided meters.

A confounding factor for me was that I have always had left, outside toe numbness and hot-foot. But never in my right toes/foot - only the left. I also have peripheral neuropathy in both lower legs, not diabetes related. I thus began a journey to see if I could fix the numbness and hot foot.

1) had the bike fit, including custom Specialized insoles (done in 2020)
2) shimmed my left cleat (done in 2020)
a) i use one glove size above my normal. for example i use extra large instead of large
b) i use one shoe size above my normal size
3) more recently shimmed my right cleat (2022)
4) tried and then removed my right cleat riser (again, not a angled shim) (2022)
5) moved both cleats to the rear as far as I could (2022)
6) just within the last week went from a 138mm saddle to a 155mm to a 165mm saddle (2022)
7) just within the last week moved my seat forward 15mm, yes I know that's a lot even though it's only about 6/10 of an inch, but I'm relatively older and don't yet have enough flexibility (2022). I've been off the bike for a year - some from laziness but almost six months due to a severe right calf injury unrelated to cycling

I may raise my saddle some to compensate for its move forward, just don't yet know how much to move it.

What clearly helped the most with outer toe numbness and hot foot in my left foot was moving the cleats completely to the rear. Second best was shimming the left cleat and the bike fit. That's where the left shim came from. The fit mostly took weight off my hands.

I did 18 miles last night with all the above in place. Problems largely resolved even though it's a sample size of one.

Next on the list of things to try if the above don't continue to work include:

https://mid-foot-cycling.com/
https://www.g8performance.com/insole...ievers-bundle/

I do not have any affiliation to any product mentioned in this post.

Glenn
Thanks, I had a Retul fit in July. They did not make any measurements of my body. I suspect I have some sort of imbalance in my torso because I sit a little cockeyed on the saddle and my left hamstring will hurt on a harder effort. I don't feel like wasting more money. Thanks for your input. I do think a tru 45/55 imbalance is a problem for me but do not know the solution.
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Old 09-13-22, 11:21 AM
  #33  
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165 mm vs. 172 mm is a 4% difference.
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Old 09-19-22, 07:29 PM
  #34  
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Originally Posted by GhostRider62 View Post
Thanks, I had a Retul fit in July. They did not make any measurements of my body. I suspect I have some sort of imbalance in my torso because I sit a little cockeyed on the saddle and my left hamstring will hurt on a harder effort. I don't feel like wasting more money. Thanks for your input. I do think a tru 45/55 imbalance is a problem for me but do not know the solution.
May I ask why you moved your saddle forward? Were you stretching to reach the right part of the bars, or did you tend to "ooze" forward while on the saddle and in all this powerful pedaling?

And, do you find yourself pushing yourself back toward the rear of the saddle?
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Old 09-19-22, 08:16 PM
  #35  
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Originally Posted by Road Fan View Post
May I ask why you moved your saddle forward? Were you stretching to reach the right part of the bars, or did you tend to "ooze" forward while on the saddle and in all this powerful pedaling?

And, do you find yourself pushing yourself back toward the rear of the saddle?
I know in my case when I went to the wider saddle that it was a much better fit to my sit-bones and it helped with left toe hot-foot and numbness. No stretching to reach the right part of the bar. Given that I don't have much flexibility and am a major clyde I'm already on a short stem. As/when flexibility improve I should be able to lengthen the stem without a reach problem. I'm tall and have long arms.

I did feel like I was "oozing" forward on the saddle prior to the moving the saddle forward, yes. Nothing about my pedaling compared to most on the forum could be considered "powerful."

Yes, I did find myself pushing back toward the rear of the saddle to get the sit-bones just right fore and aft before I moved the saddle forward. Current saddle tilt is negative 2 degrees. Think I should make that flat?

Thoughts, ideas?

Thanks.

Glenn
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Old 09-20-22, 04:25 AM
  #36  
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One approach to the oozing is to move the saddle forward so that "after the ooze" your sitbones are in the right places on the saddle. Another is to gently start to raise the nose of the saddle to have gravity add a little force in the rearward direction, acting on your pelvis to keep it from forward motion, however slow. As a test, sliding the saddle forward is good since it shows that you are not on the saddle as you should be.

By "negative 2 degrees" do you mean that the nose is up or down?

In the current saddle position, are you tending to slide forward as you pedal? If so I would gradually move the saddle nose up. This is where a micro-adjusting seat post with two bolts, not just a single clamp bolt with the mount rotation being limited by a ratchet, helps a lot to find the best spot. The best spot might be between ratchet points. If you raise the saddle nose slowly you should feel the pressure on your underside moving. The pressure should be on your sitbones and not of significant magnitude in front ot them, and you should not be using your legs to hold yourself in place. You should be sitting on your saddle with stability with your back straight up and with your pelvis and back rotated forward to reach the hoods and preferably the drops.

For me this last paragraph is really important in fitting myself. It works for Mrs. Road Fan as well and for a tri-winning neighbor lady whom I helped once. It also mirrors a lot of what Carbonfiberboy recommends, due to his long experience and his research.
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Old 09-20-22, 07:49 AM
  #37  
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Originally Posted by Road Fan View Post
By "negative 2 degrees" do you mean that the nose is up or down?

In the current saddle position, are you tending to slide forward as you pedal? If so I would gradually move the saddle nose up. This is where a micro-adjusting seat post with two bolts, not just a single clamp bolt with the mount rotation being limited by a ratchet, helps a lot to find the best spot.
Yes, 2 degrees nose down. Yes, sliding forward as I pedal. My Domane SLR7 seat post is a two bolt.

Thanks

Glenn
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Old 09-20-22, 08:26 PM
  #38  
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I would suggest you try to raise the nose of the saddle in small increments, maybe 1 mm measured against the seat tube or ½ or ¼ degree measured with a decent level. As you raise it your oozing forward will slow down and eventually you'll perch on the saddle with some stability. At that position the nose might be pointing somewhat upward, but that's ok, your body is not on the nose of the saddle, it's on the wide part. But while you sit on the wide part there might be pressure in front of the sitbones, on the perineum. This could cause abrasion if your saddle is too high, and numbness if the pressure is on the perineum If you have these you need to gradually lower the nose down, noticing how the pressure points change.

In effective saddle height, this all tends to reduce actual saddle height as measured to the sit-bone contact point, as well as how it all feels, your term, "effective saddle height."
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Old 09-20-22, 08:31 PM
  #39  
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Originally Posted by Road Fan View Post
I would suggest you try to raise the nose of the saddle in small increments, maybe 1 mm measured against the seat tube or ½ or ¼ degree measured with a decent level. As you raise it your oozing forward will slow down and eventually you'll perch on the saddle with some stability. At that position the nose might be pointing somewhat upward, but that's ok, your body is not on the nose of the saddle, it's on the wide part. But while you sit on the wide part there might be pressure in front of the sitbones, on the perineum. This could cause abrasion if your saddle is too high, and numbness if the pressure is on the perineum If you have these you need to gradually lower the nose down, noticing how the pressure points change.

In effective saddle height, this all tends to reduce actual saddle height as measured to the sit-bone contact point, as well as how it all feels, your term, "effective saddle height."

I think that's a good plan.

Thank you.

Glenn
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Old 09-21-22, 07:41 AM
  #40  
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Originally Posted by GAtkins View Post
I think that's a good plan.

Thank you.

Glenn
Glad I can help!
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