Is it possible to adjust reported power from power meters?

I have 3 power meters and a Tacx Neo and they all report different power. Is there a way to adjust their reported power so I can get them in sync?

Tacx Neo - Let’s assume this one is correct.
SRAM Quarq Red AXS = +3%
Stages left side X9 Gen2 = +10%
SRAM Quarq XX1 Eagle = +11%

I swap between different bikes and trainer and want to be able to train on them without having to adjust my FTP-settings for every single ride because they report different power.
They all report consistent power, but the reported power differs a lot. Would be really nice if I could just adjust the reported power -3%, -10% and -11% so I could get them in sync. How hard can it be to make a feature like this available in the Stages and Quarq-apps?

Here are some comparisons I did with the power meters on the Neo:
https://zwiftpower.com/analysis.php?set_id=35638
https://zwiftpower.com/analysis.php?set_id=35069
https://zwiftpower.com/analysis.php?set_id=34996

Magnus

No. They will never be in sync. With PowerMatch you can add an offset, but an offset is not the same as being in sync. Slopes, peak, etc. would be different, and would still use, if the Neo, the trainer’s power calculations, and then tack on an offset to it.

The power readings won’t overlap and look like a single line, but can get closer.

They do not have to be 100% in sync, but more like in the same 2-3% range would be nice, so the TSS wont be ruined and I dont have to do different power in the same workouts because I use different bikes.

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Apparently you should expect drive chain losses to make your power meters to read 3-5% higher than your Tacx (or more if it’s a mess). Which would account for your Red axs.

Not much use for you, but 4iiii meters let you scale the power output - the idea is to adjust for right/left balance on single sided power meters, or to match to other power meters for single and double sided.

(There should be something on Zwift that shows the scale factor people with 4iiiis are using. )

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As much as it pains me to say it, given the differences, I’m not sure we can assume the Neo is correct.

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I was convinced that my Neo was giving me low power until I got the AXS and it turned out that AXS and NEO was mostly in sync. I find it really weird that my two MTB power meters from two different manufactures (SRAM and Stages) are so in sync and still so far away from AXS/SRAM and Neo.

As long as these powermeters still are training equipment and not virtual racing equipment I wonder why it’s not possible to offset the power on Stages and Quarq.

deleted - replying to wrong thread

I contacted SRAM support and got some help. Using the AXS-app it is possible to adjust reported power by adjusting Slope in the settings. This can be done in 0.5% intervals, so now my Neo and two Quarqs are in sync. Happy Quarq-days!

Factory slope:
https://zwiftpower.com/analysis.php?set_id=37089

Adjusted -12.5% slope:
https://zwiftpower.com/analysis.php?set_id=37119

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Hello magnusc,
I am having the same problem you have:

  • AXS XX1 - +10% Vs NEO.

How do you adjust the slope down? It is just to push down -0.5 until you achieve the same two metrics? Do you need to do a lot of trial? Any guidance on process will be very helpful.

At the same time, any guidance from Quarq on why do we have this deviation?

Thanks in advance
Regards

Make sure you do the test inside on the roller. Do not compare your inside power to what you can do outside. Riding inside is very different.

If your AXS is reporting 10% more power than the Neo when using it with the Neo then you ned to tap the -0.5-button 20 times to get the power to go down 10%.

I recommend doing a new test on the Neo after you have done the Slope-adjustment to confirm that the changes had the effect you wanted.

I sendt in my Stages to Stages and they testet it and sendt it back with a paper confirming that it passed the test.

My conclusion is that power-meters and rollers are not very accurate at all, so virtual racing is not something I take to seriously.

Thanks for the response Magnusc.

I have tested my Neo against my Assioma pedals and both have same measurements, but at the time I do it against my Quarq Dzero XX1, my Quarq is up by 10%. I just want to have all aligned as it is a bit crazy to have different type of measures.

I will do the slope adjustment and get it along with my Assioma’s.

Any recommendation that you suggest me to do?

Thank you

Does it make sense to adjust for L/R balance?

I know I’m 48/52 LR respective.

Given one of my bikes has a left-only crank PM, should I bump the slope adjust by 2% and then test?

You could adjust the power readings on the *.fit file via fitfiletools.com then upload manually to intervals.icu/Strava etc to be able to compare runs.

Or import the various *.fit files into Golden Cheetah and adjust the power in there, and compare etc, You can also export in various formats from GC.