Power balance on different bikes

Apr 16, 14 7:46

Post #1 of 29 (6070 views)

Disclosure: I work for power2max power meters.

I was a little hesitant to post it since people might misunderstand my intentions, but my curiosity prevailed.

Context: I have our power meters on my 3 bikes: road, TT, MTB. Nice thing about working in a power meter company I guess. The power2max determines left-right balance by comparing the relative size of the two power phases per crank revolution. I.e. per 360 degrees there are two peaks and two troughs in power (like a sine curve). It goes from trough to trough. So it's not an independent measurement of the two sides, but captures systematic differences. What it cannot measure is how much the push component is and how much the pull component of the opposite leg is.

What I noticed:
- On my road bike my balance is between 48-52 (L-R) and 46-54. Recently, after a hip issue on the left hand side more towards 46-54
- On my TT bike (same shoes and pedals) it's between 50-50 and 51-49
- On my MTB yesterday it was 52-48 (different shoes, pedals)

I have played a bit with my position on my road bike and recently moved my saddle forward 5mm and up 5mm, which made it easier to get "over the top". The balance didn't change, though.

I am really curious what causes these differences between the bikes. I thought on the TT bike my forward position would change the push-pull dynamic, but I can't quite tell why on the MTB - where the saddle is also back - I have more of a left emphasis.

What are other people's experiences with their balance? I don't know if it's significant or not, just curious.

Best
Nicolas

---
power2max
http://www.power2max.com/northamerica
official power meter of Movistar Team

Re: Power balance on different bikes [power2max] [ In reply to ]

Apr 16, 14 7:48

Post #2 of 29 (6065 views)

coggan got some vectors recently and has been posting l/r data from his rides.

seems his L/R balance changes quit a bit from day to day on the *same* bike.

Kat Hunter reports on the San Dimas Stage Race from inside the GC winning team
Aeroweenie.com -Compendium of Aero Data and Knowledge
Freelance sports & outdoors writer Kathryn Hunter

Re: Power balance on different bikes [power2max] [ In reply to ]

Apr 16, 14 7:53

Post #3 of 29 (6055 views)

I would suspect that on your TT bike, you keep a fairly constant power throughout the ride. On the road bike it fluctuates and on the MTB it fluctuates ever more. I do not think your powerbalance will be the same at 75% of your FTP as it is at 95% of your FTP or as it is at 110% of your FTP. So on your road bike if you are bouncing between 110% of your FTP and 80% of your FTP and on your TT you are going between 85% and 95%, I would not be suprised if your balance was different, even if the rides had the same overall average power.

Re: Power balance on different bikes [jackmott] [ In reply to ]

Apr 16, 14 7:56

Post #4 of 29 (6052 views)

There is good variation and even more, you can see clearly when there is injury. I rode a ironman at 27/73 with the major lost in power that goes with it.

I see the number fluctuation when tired, on different bike etc. But for most key session, it was pretty consistent. The next challenge will be to see what we do with those numbers. There hasn't been much reliable data on this until Garmin vector was brought to the market. now that we can daily monitor this, it should be interesting to see what comes out.

Jonathan Caron / Professional Coach / ironman champions / age group world champions
Jonnyo Coaching
Instargram

Last edited by: jonnyo: Apr 16, 14 8:08

Re: Power balance on different bikes [jonnyo] [ In reply to ]

Apr 16, 14 7:59

Post #5 of 29 (6041 views)

jonnyo wrote:

There is good variation and even more, you can see clearly when there is injury. I rode a ironman at 27/63 with the major lost in power that goes with it.

What happened to the other 10%?

Re: Power balance on different bikes [chaparral] [ In reply to ]

Apr 16, 14 8:03

Post #6 of 29 (6033 views)

HI Chaparral,

I can't really confirm that hypothesis based on my glancing at the data because I have done both very even and uneven rides on the road bike and haven't seen that my balance was 50-50 on steady portions. I found that on standing hill reps it was more balanced.

I guess I should do a bit more a systematic dig into the data...

---
power2max
http://www.power2max.com/northamerica
official power meter of Movistar Team

Re: Power balance on different bikes [bricklayer] [ In reply to ]

Apr 16, 14 8:06

Post #7 of 29 (6027 views)

bricklayer wrote:

jonnyo wrote:

There is good variation and even more, you can see clearly when there is injury. I rode a ironman at 27/63 with the major lost in power that goes with it.

What happened to the other 10%?

Dam! 27/73! and a 50 watts lost in power! made for a interesting powerfiles as getting out of the saddles, the % would come back to normal

Jonathan Caron / Professional Coach / ironman champions / age group world champions
Jonnyo Coaching
Instargram

Re: Power balance on different bikes [power2max] [ In reply to ]

Apr 16, 14 9:42

Post #8 of 29 (5982 views)

power2max wrote:

What I noticed:
- On my road bike my balance is between 48-52 (L-R) and 46-54. Recently, after a hip issue on the left hand side more towards 46-54
- On my TT bike (same shoes and pedals) it's between 50-50 and 51-49
- On my MTB yesterday it was 52-48 (different shoes, pedals)

Look at pedal force-pedal speed (or, if you have the same length cranks on each bike you can look at the equivalent torque-cadence), and tag the points by the L/R balance.

Re: Power balance on different bikes [power2max] [ In reply to ]

Apr 16, 14 10:00

Post #9 of 29 (5971 views)

I'm part of the old school pedaling technique of pulling up on the back side of the pedal stroke just because I've done it for so many years.

On my P2M power meter I'm getting (L/R) 52/48 to 50/50 and I think I'm getting up to 52% because I'm pulling up more with my right leg than my left leg. I really have no way of determining it for sure though.

I only have the P2Max on my road bike but my seat and hip angles are very similar to my tri bike which has a Powertap G3 on it. My power outputs are very similar between the two bikes. I don't have a way to measure power on my MTB.

jaretj

Re: Power balance on different bikes [jackmott] [ In reply to ]

Apr 16, 14 11:20

Post #10 of 29 (5948 views)

jackmott wrote:

coggan got some vectors recently and has been posting l/r data from his rides.

seems his L/R balance changes quit a bit from day to day on the *same* bike.

Is there anywhere to see this data publicly?

Has there been any new info on the use of this data? I have a P2M (Type S) and my rides are consistently between 42/58 and 45/55. My power output is good I think but I'm surprised to see this much of an asymmetry.

Re: Power balance on different bikes [power2max] [ In reply to ]

Apr 16, 14 19:02

Post #11 of 29 (5881 views)

power2max wrote:

Disclosure: I work for power2max power meters.

I was a little hesitant to post it since people might misunderstand my intentions, but my curiosity prevailed.

Context: I have our power meters on my 3 bikes: road, TT, MTB. Nice thing about working in a power meter company I guess. The power2max determines left-right balance by comparing the relative size of the two power phases per crank revolution. I.e. per 360 degrees there are two peaks and two troughs in power (like a sine curve). It goes from trough to trough. So it's not an independent measurement of the two sides, but captures systematic differences. What it cannot measure is how much the push component is and how much the pull component of the opposite leg is.

What I noticed:
- On my road bike my balance is between 48-52 (L-R) and 46-54. Recently, after a hip issue on the left hand side more towards 46-54
- On my TT bike (same shoes and pedals) it's between 50-50 and 51-49
- On my MTB yesterday it was 52-48 (different shoes, pedals)

I have played a bit with my position on my road bike and recently moved my saddle forward 5mm and up 5mm, which made it easier to get "over the top". The balance didn't change, though.

I am really curious what causes these differences between the bikes. I thought on the TT bike my forward position would change the push-pull dynamic, but I can't quite tell why on the MTB - where the saddle is also back - I have more of a left emphasis.

What are other people's experiences with their balance? I don't know if it's significant or not, just curious.

Best
Nicolas

Apart from general fit dimension, check your Q-factor between road and TT bike.
The different pedals/shoes/cleat position on MTB can also affect this.

And you should expect to see day to day variations in any case.

TBH though, I think the data from this sort of both leg combined left-right split measurement isn't particularly insightful (due to the inability as you point out to distinguish what components are due to which leg). You probably need independent crank or pedal force data to get a better view as to what's going on.

You might find that your actual balance is the other way around and you're barking up the wrong tree.

But I note you are seeing differences using the same means of measurement, which is of course interesting, I just think it can be a misleading indicator and is to be treated with caution before considering what, if any, changes you choose to make. What appears balanced with this sort of left-right split, may well not be, and vice versa.

Re: Power balance on different bikes [power2max] [ In reply to ]

Aug 28, 14 5:22

Post #12 of 29 (5587 views)

I have several hundred rides on my Wattbike Pro (indoor trainer) and Rotor Power systems - both bikes set up identically with 170mm cranks..

Wattbike - L 52% / R 48%
Rotor Power - L 53% / R 47%

First ride on my new S-Works Type S Power2Max..

Power2Max - L 47% / R 53%

Explanation??

Re: Power balance on different bikes [power2max] [ In reply to ]

Aug 28, 14 6:32

Post #13 of 29 (5546 views)

I know you don't like static torque tests, but I would do a static torque test with each power meter, testing left and right cranks pointing forwards separately to see if there is a difference. I've found power meters can vary in their relative left and right measurements.

Re: Power balance on different bikes [Sim0n0] [ In reply to ]

Aug 28, 14 7:59

Post #14 of 29 (5517 views)

Programming error (someone switched L and R)?

Do you use the same head unit / program to display the data?

Did you do one-leg tests to see whether the data is (reasonably) correct?

Re: Power balance on different bikes [MrSkinny] [ In reply to ]

Aug 28, 14 8:47

Post #15 of 29 (5489 views)

MrSkinny wrote:

Programming error (someone switched L and R)?

Do you use the same head unit / program to display the data?

Did you do one-leg tests to see whether the data is (reasonably) correct?

My first thoughts were that it's either a programming error and their L/R data analysis is very accurate or the programming is good and their L/R data analysis is a waste of time.

Or all L/R data is a waste of time ;)

I haven't tried single leg only yet..

Re: Power balance on different bikes [Sim0n0] [ In reply to ]

Aug 28, 14 23:06

Post #16 of 29 (5427 views)

Sim0n0 wrote:

I have several hundred rides on my Wattbike Pro (indoor trainer) and Rotor Power systems - both bikes set up identically with 170mm cranks..

Wattbike - L 52% / R 48%
Rotor Power - L 53% / R 47%

First ride on my new S-Works Type S Power2Max..

Power2Max - L 47% / R 53%

Explanation??

Could be a multitude of things.

Was this on Wattbike as well?

Re: Power balance on different bikes [Watt Matters] [ In reply to ]

Aug 29, 14 0:55

Post #17 of 29 (5405 views)

Watt Matters wrote:

Sim0n0 wrote:

I have several hundred rides on my Wattbike Pro (indoor trainer) and Rotor Power systems - both bikes set up identically with 170mm cranks..

Wattbike - L 52% / R 48%
Rotor Power - L 53% / R 47%

First ride on my new S-Works Type S Power2Max..

Power2Max - L 47% / R 53%

Explanation??

Could be a multitude of things.

Was this on Wattbike as well?

The Wattbike is a stand alone trainer

http://wattbike.com/uk/wattbike

Re: Power balance on different bikes [power2max] [ In reply to ]

Aug 29, 14 4:21

Post #18 of 29 (5373 views)

In short bike fit.... Inclusive of your pedal and shoe combinations....
And the fit and support of those shoes.. Ie arch support and varus etc..

As a test try to normalise your position across bikes and contact points and see if your results converge....ie same pedals and shoes, saddles and at least saddle position relative to bb.. Height set back and angle.

Be interested to see what changes if anything... Tks

Re: Power balance on different bikes [shadwell] [ In reply to ]

Aug 29, 14 7:59

Post #19 of 29 (5337 views)

shadwell wrote:

In short bike fit.... Inclusive of your pedal and shoe combinations....
And the fit and support of those shoes.. Ie arch support and varus etc..

As a test try to normalise your position across bikes and contact points and see if your results converge....ie same pedals and shoes, saddles and at least saddle position relative to bb.. Height set back and angle.

Be interested to see what changes if anything... Tks

The bikes are identical to the mm (measured with my Retul system)

On my Wattbike and Rotor Power my L/R could go out to L 54% / R 46% on a low intensity recovery session, but it was generally L 53% / R 47%

76 miles today and the Power2Max power balance was the same as the first ride L 47% / R 53%

Single leg pedaling corresponded to the correct side, so it doesn't appear to be a firmware issue

Last edited by: Sim0n0: Aug 29, 14 10:50

Re: Power balance on different bikes [Sim0n0] [ In reply to ]

Aug 29, 14 12:42

Post #20 of 29 (5268 views)

Sim0n0 wrote:

shadwell wrote:

In short bike fit.... Inclusive of your pedal and shoe combinations....
And the fit and support of those shoes.. Ie arch support and varus etc..

As a test try to normalise your position across bikes and contact points and see if your results converge....ie same pedals and shoes, saddles and at least saddle position relative to bb.. Height set back and angle.

Be interested to see what changes if anything... Tks

The bikes are identical to the mm (measured with my Retul system)

On my Wattbike and Rotor Power my L/R could go out to L 54% / R 46% on a low intensity recovery session, but it was generally L 53% / R 47%

76 miles today and the Power2Max power balance was the same as the first ride L 47% / R 53%

Single leg pedaling corresponded to the correct side, so it doesn't appear to be a firmware issue

Re: Power balance on different bikes [Sim0n0] [ In reply to ]

Aug 29, 14 16:34

Post #21 of 29 (5244 views)

Sim0n0 wrote:

Watt Matters wrote:

Sim0n0 wrote:

I have several hundred rides on my Wattbike Pro (indoor trainer) and Rotor Power systems - both bikes set up identically with 170mm cranks..

Wattbike - L 52% / R 48%
Rotor Power - L 53% / R 47%

First ride on my new S-Works Type S Power2Max..

Power2Max - L 47% / R 53%

Explanation??

Could be a multitude of things.

Was this on Wattbike as well?

The Wattbike is a stand alone trainer

http://wattbike.com/uk/wattbike

I'm aware of what the Wattbike is.

The question was whether the Power2Max data was collected while training on the Wattbike.

The OP gave data from the Rotor while training on the Wattbike, showing the Rotor and Wattbike reported a similar power balance, but they did not say if the Power2Max data was from a session on the Wattbike enabling a comparison with Wattbike data.

There are still a multitude of reasons why the difference might exist, but it would help to know how the Power2Max and Wattbike reported power balance compares - mainly because they use the same means of measurement, i.e. left/right is net torque from both legs measured based on crank position (whichever is forward of the bottom bracket), while the Rotor measures crank torque on each arm independently. It's a different measurement and means different things.

The Rotor and Wattbike reported the same power balance even though they are different measurements, which is certainly feasible and not overly surprising, but seeing different values would not be a surprise either.

However we should expect the Wattbike and the Power2Max to provide the same power balance values, since they are both measuring net torque from both legs and the left/right split is based on crank arm position.

If those two devices used together report a different power balance, then I'd suggest that one or both of them has an accuracy issue.

Re: Power balance on different bikes [Sim0n0] [ In reply to ]

Aug 29, 14 17:10

Post #22 of 29 (5233 views)

Sim0n0 wrote:

On my Wattbike and Rotor Power my L/R could go out to L 54% / R 46% on a low intensity recovery session, but it was generally L 53% / R 47%

76 miles today and the Power2Max power balance was the same as the first ride L 47% / R 53%

Single leg pedaling corresponded to the correct side, so it doesn't appear to be a firmware issue

You should expect to have different L/R balance between a soft pedal and a long ride.

I don't really think we should pay too much attention to that number being spit out at this point. We have no idea what to really do with it. 50/50 might not even be good for you fit wise, it might mean you are leaning right which makes it impossible for you to use your left leg fully which is actually stronger than your left. Maybe one day it will tell us you need to pedal harder with your right on purpose cause it is weak, but right now we can't tell if that is the case, or your body is assymetrical (it is), or your fit is wrong, or perhaps there is some other weird issue like decreased blood flow to one leg in the drops.

---------------------
Jordan Oroshiba --- Roadie invading Triathlete space for knowledge access

Re: Power balance on different bikes [joroshiba] [ In reply to ]

Aug 29, 14 20:48

Post #23 of 29 (5204 views)

joroshiba wrote:

Sim0n0 wrote:

On my Wattbike and Rotor Power my L/R could go out to L 54% / R 46% on a low intensity recovery session, but it was generally L 53% / R 47%

76 miles today and the Power2Max power balance was the same as the first ride L 47% / R 53%

Single leg pedaling corresponded to the correct side, so it doesn't appear to be a firmware issue

You should expect to have different L/R balance between a soft pedal and a long ride.

I don't really think we should pay too much attention to that number being spit out at this point. We have no idea what to really do with it. 50/50 might not even be good for you fit wise, it might mean you are leaning right which makes it impossible for you to use your left leg fully which is actually stronger than your left. Maybe one day it will tell us you need to pedal harder with your right on purpose cause it is weak, but right now we can't tell if that is the case, or your body is assymetrical (it is), or your fit is wrong, or perhaps there is some other weird issue like decreased blood flow to one leg in the drops.

or the data is wrong

Re: Power balance on different bikes [Watt Matters] [ In reply to ]

Aug 30, 14 1:06

Post #24 of 29 (5178 views)

I'm playing with the Pioneer system which is a true L/R measure and it is surprising (with the proper software to analyze) how much fit, cadence, effort, etc can affect your l/r balance...we can debate its value on another thread.

It can also very daily based on bike fit and fatigue. I wouldn't expect to see massive differences such as 30-70 however.

Re: Power balance on different bikes [Watt Matters] [ In reply to ]

Sep 2, 14 3:20

Post #25 of 29 (5103 views)

Watt Matters wrote:

Sim0n0 wrote:

Watt Matters wrote:

Sim0n0 wrote:

I have several hundred rides on my Wattbike Pro (indoor trainer) and Rotor Power systems - both bikes set up identically with 170mm cranks..

Wattbike - L 52% / R 48%
Rotor Power - L 53% / R 47%

First ride on my new S-Works Type S Power2Max..

Power2Max - L 47% / R 53%

Explanation??

Could be a multitude of things.

Was this on Wattbike as well?

The Wattbike is a stand alone trainer

http://wattbike.com/uk/wattbike

I'm aware of what the Wattbike is.

The question was whether the Power2Max data was collected while training on the Wattbike.

The OP gave data from the Rotor while training on the Wattbike, showing the Rotor and Wattbike reported a similar power balance, but they did not say if the Power2Max data was from a session on the Wattbike enabling a comparison with Wattbike data.

There are still a multitude of reasons why the difference might exist, but it would help to know how the Power2Max and Wattbike reported power balance compares - mainly because they use the same means of measurement, i.e. left/right is net torque from both legs measured based on crank position (whichever is forward of the bottom bracket), while the Rotor measures crank torque on each arm independently. It's a different measurement and means different things.

The Rotor and Wattbike reported the same power balance even though they are different measurements, which is certainly feasible and not overly surprising, but seeing different values would not be a surprise either.

However we should expect the Wattbike and the Power2Max to provide the same power balance values, since they are both measuring net torque from both legs and the left/right split is based on crank arm position.

If those two devices used together report a different power balance, then I'd suggest that one or both of them has an accuracy issue.

No, the Wattbike is a stand alone static training bike - not a turbo trainer. The data I have is from the Wattbike and also a Rotor Power (fitted to two different bikes) - both of these power meters measure around 53% L / 47% R

The Power2Max has replaced the Rotor Power on one of my bikes - ALL the bikes have the same crank length and are set up very close (measured by my Retul). The Power2Max measures 47% L / 53% R

Same bike set ups - different data. Either Rotor Power and Wattbike are wrong or Power2Max is wrong..

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