L/R% accuracy?

Discuss light weight issues concerning road bikes & parts.
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eaglejackson
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Joined: Wed Aug 27, 2014 5:26 am
Location: PNW

by eaglejackson

How accurate are the L/R balance on power meters? I've had a Quara DFour on one bike and it typically reads 49/51% or 50/50%. I got a Shimano 9100-P on my other bike and it reads 54/46%. Both bikes are Parlee Z5 SLi with Di2.

by Weenie


AZR3
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Location: Az USA

by AZR3

https://www.bikeradar.com/us/road/gear/ ... iew-51582/

Read that for L/R issues with Shimano’s power meter

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silvalis
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by silvalis

They are different meters located in different parts of the drivetrain.
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Kazyole
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Joined: Tue Apr 02, 2013 1:45 am
Location: NYC

by Kazyole

As AZR3 mentioned, it's a known issue with the 9100-P.

Your overall power number will be about right, but the L/R data is unreliable. Hopefully it's something that shimano can fix with a firmware update in the future.

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ms6073
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Location: Houston, Texas

by ms6073

Kazyole wrote:
Sun Mar 11, 2018 11:31 pm
Hopefully it's something that shimano can fix with a firmware update in the future.
While I am not overly concerned with L/R balance, given the lack of uniformity amongst the other powermete offerings, seems to me that none are very reliable outside of controlled environments.
Michael - The Anaerobic Threshold is neither...

eaglejackson
Posts: 253
Joined: Wed Aug 27, 2014 5:26 am
Location: PNW

by eaglejackson

AZR3 wrote:
Sun Mar 11, 2018 11:05 pm
https://www.bikeradar.com/us/road/gear/ ... iew-51582/

Read that for L/R issues with Shimano’s power meter
Thanks. Yes, that's the same issue I'm experiencing. The Bike Radar reviewer's experience was not a one-off, as it appears Shimano is trying to claim. I hope it gets fixed in a firmware update.

c60rider
Posts: 219
Joined: Mon Feb 27, 2017 11:12 pm

by c60rider

Most of the crank based power meters will measure left/right balance by measuring power produced from the 12 o'clock position to the 6 o'clock position for each crank. It gives you a guide but won't break it down with any accuracy. The Rotor2in measures both sides so for that one you will get accurate left right balance as any dual sided power meter will (Shimano one aside it appears!) I don't think it's really that important and what will you do about it? Having had the symptoms associated with endofibrosis for 25 years before finally getting surgery if anyone will have an imbalance it will be me but even then it's rarely worse than 48:52% left to right these days and I've done nothing specific to train the left leg now it's working right. There's far more gains to be made with working on threshold power, maximal sprint power and repeatability etc than to worry about a 1 or 2% difference from one leg to the other. Assuming that's not the equipment itself giving you false data and you really are equal! It's quite normal to have one side slightly more dominant than the other and power meters pick up the most subtle of differences.

cunn1n9
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Joined: Sat Jan 15, 2011 1:24 am

by cunn1n9

eaglejackson wrote:
AZR3 wrote:
Sun Mar 11, 2018 11:05 pm
https://www.bikeradar.com/us/road/gear/ ... iew-51582/

Read that for L/R issues with Shimano’s power meter
Thanks. Yes, that's the same issue I'm experiencing. The Bike Radar reviewer's experience was not a one-off, as it appears Shimano is trying to claim. I hope it gets fixed in a firmware update.
I have 2 of these powermeters and both give me 52/48 (L/R) for every ride. This is very consistent but my old Vector 2’s where 48/52 (L/R) which is round the other way.

Attached is the Garmin Connect screen for a 235km 4500m ride I did a day ago where the elevation ranged from 300m to 1800m above sea level so a lot of temp change.

Not sure what to make of the claim my left leg is stronger than my right leg as this is different than the Vectors but it’s just a single data point so hardly conclusive. If it’s firmware I’m sure Shimano will fix it. But if it’s hardware then I’m wondering what they do.
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ms6073
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Joined: Fri Jul 23, 2004 8:24 pm
Location: Houston, Texas

by ms6073

cunn1n9 wrote:
Mon Mar 12, 2018 10:49 am
This is very consistent but my old Vector 2’s where 48/52 (L/R) which is round the other way.
Maybe the firmware was reversed. 8)
Michael - The Anaerobic Threshold is neither...

robertbb
Posts: 266
Joined: Thu Jul 23, 2009 3:35 am
Location: Melbourne, Australia

by robertbb

cunn1n9 wrote:
Mon Mar 12, 2018 10:49 am
eaglejackson wrote:
AZR3 wrote:
Sun Mar 11, 2018 11:05 pm
https://www.bikeradar.com/us/road/gear/ ... iew-51582/

Read that for L/R issues with Shimano’s power meter
Thanks. Yes, that's the same issue I'm experiencing. The Bike Radar reviewer's experience was not a one-off, as it appears Shimano is trying to claim. I hope it gets fixed in a firmware update.
I have 2 of these powermeters and both give me 52/48 (L/R) for every ride. This is very consistent but my old Vector 2’s where 48/52 (L/R) which is round the other way.

Attached is the Garmin Connect screen for a 235km 4500m ride I did a day ago where the elevation ranged from 300m to 1800m above sea level so a lot of temp change.

Not sure what to make of the claim my left leg is stronger than my right leg as this is different than the Vectors but it’s just a single data point so hardly conclusive. If it’s firmware I’m sure Shimano will fix it. But if it’s hardware then I’m wondering what they do.
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3 peaks. Killer ride, good stats!
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by Weenie


eaglejackson
Posts: 253
Joined: Wed Aug 27, 2014 5:26 am
Location: PNW

by eaglejackson

Congrats on such an epic ride!

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