New power meter measuring 20% lower than old power meter

I was fortunate to get my hands on a pair of Favero Assioma Duo Shi power meters over Thanksgiving, these were to replace my older first gen Favero Duos. I followed the specs to install and the new power pedals are measuring 20% lower than the first gen pairs. I even ran the new ones through @dcrainmaker 's calibration method but the measurements still read 20% lower :frowning: .

I realize in the long term that as long as the measurement is consistent, there should be no issues as far as training is concerned; I’d just need to retest my FTP which frankly wouldn’t be a bad idea anyhow. However, I’m still bothered by the large difference in measurements between the old pedals and the new, a 20% delta (higher or lower) can’t be normal. Does anyone have any suggestions on what may be causing the difference in readings?


EDIT: I should clarify that I’m measuring according to RPE. I realize that’s not 100% accurate, but if I don’t look at the power and just go off feel, the power is consistently 20% lower than where I think it should be.

Reach out to Assioma support. They can do some remote diagnostics on the pedals. Might be good to make sure everything’s working.


Don’t jump to conclusions until you have tested your FTP. There shouldn’t be a 20 % difference between power meters, but it happens. Once you have retested and the difference persists, contact Assioma’s support.

When my Elite Suito was new, it happily agreed with my Quarq DZero. Now they are about 15–20 W apart at FTP, and both, the offset and the slope of both are different.

And when I got my first power meter, it’d show fantastic numbers for the first 3 weeks or so (think top end world tour pro — which I am not :crazy_face:). Then readings normalized and stayed there. .


Did you try the static weight test? Is the crank length set correctly? Are the pods free from the crank?


Welp, turns out my new duo shi are spot on with my 2019 Wahoo Kickr in terms of power. My old duo’s on the other hand are 20% higher than both the Shi’a and the Kickr :smiling_face_with_tear:


Ahhh, the joys of owning more than one power measuring device :stuck_out_tongue:


Lol, I suppose it’s a good problem eh? But talk about eating humble pie, my FTP just dropped 20%.

Yeah, you are among a large & growing crew of people who discover a device is not exactly “accurate”.

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You could just set the adjustment factor in the pedals to 1.2 to report 20% more.
But the interesting question first is which one is right, assuming that the RPE calibration is correct and that there is indeed a big difference between the 2.

Do you have outside rides where you can compare average power / speed to online calculators? A 20% error should be possible to distinguish.

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Thanks for the advice! Unfortunately I’m not sure if I did something wrong.

I used and on a segment about 5 miles long and 1.5% grade that I did last week. Bikecalculator shows that at the reported average watts of 257, my speed would have been 13.6MPH when Strava records it as 16.3MPH; this would mean that I was putting out more watts than my old power meters were reporting which is the opposite of my problem :thinking:.

I would put more than a grain of salt on any estimate like that. Real CDA, rolling resistance and GPS error are not something I would rely on for comparing to a power meter.

At this point, doing static hang tests and live comparison with a 2nd power device (like a good quality trainer) is the only proper thing to investigate this issue.


Well in that case I guess it’s done. The new powermeters are spot on with my 2019 Wahoo Kickr and I have no reason to believe they could both be wrong. I’ve put my older Favero’s through the ringer, I’ve crashed a couple times with them on and while there’s no visible damage, it’s possible the meters were borked somehow.

It’s just…wow. Going from a 300 watt FTP to 240 just seems way off, but doing 240 watts right now actually feels like threshold :(. I guess this explains why my weight loss hasn’t been going as smoothly as I’d have liked, my calories expended were all out of whack. I already messaged Favero and am waiting for them to respond, I’ll probably do a FTP test next week too.

  1. This is why accuracy matters, not just consistency.
  2. There are ways to validate accuracy both statically and dynamically, but hardly anyone does them.

Quite a bit to unpack with your reply:

  • Your FTP didn’t really change in any way. It’s the same now as it was before you paid for/and installed the new power meter. What changed is the “tape measure” you used.

  • All this case does is confirm that the state of “power measurement” in the cycling industry is far more variable than those product makers are willing to admit. When we look at the range of devices in use, how and when they measure “power” and user implementations are not all equal… the reality is that we have far more variability than anyone wants to deal with these days.

  • I don’t have any answers here other than to follow the manufacture install and calibration processes to the letter, and temper our expectations with a healthy dose of reality.

  • This heads down a VERY different road and one I am not equipped to handle with any real details. But the thing I know is that nutrition, calorie counting and weight management are not at a level that we can expect precision that the devices and data may imply.

  • Using tools and such to measure and plan can be done, but those MUST be taken along with the reality you see in person and on the scale (or any other methods of measurements). Even if you have something skewing data to an extent enough to impact weight management, you need to question it when reality doesn’t align with it. Evaluation and adjustment is needed because of accuracy issues as well as other ‘X-factors’ that aren’t captured in that data.

  • This is good, and is the reason I recommend a new FTP evaluation anytime people alter a power measuring device as well as trainers (with or without power). These can all impact the power data reported, as well as the physiological load on the body and effectively alter results.

  • I’ve seen people using the same exact power device and bike on a different trainer get different results. In those cases, it largely aligns with the difference in flywheel effect, but it’s possible other factors play into the results.

  • In any case, swapping key factors in your training equation usually necessitate a new test.


Thanks @mcneese.chad , I appreciate the in-depth response.

I know my FTP didn’t change, it’s more of the idea that the measurement could potentially be this far off. As you typed, the state of power measurement in the cycling industry is likely more variable thank users think.

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Just do the static weight test, it only takes 5 minutes but you need an accurate scale that can measure to the gram and at least 8kg of weight (I used 2 5kg weights which I had to weigh separate because of the weight limit of the kitchen scale). My assiomas were both really close to the weight on the scale (a few grams difference on the 10000g total)


Static torque check is sort of the minimum: if a power meter fails the static test, you know it’s bad–but it can pass a static check and still fail a dynamic check. But the static check is easy enough to do that I agree that it should be the first step.


This, Sir is a fantastic response.

I feel we’re at a stage where we should have a permanent power meter information thread. Much like what you discussed here.

Essentially, a no BS guide to help people understand that in general, power meters are unfortunately not the ultra precise devices that many believe them to be.

Yes, some are great. Yes, some people have great consistency, even across brands. However, that is not always the case and likely the minority of cases.

Try coaching 100 athletes, all with 3 different power meters across their various bikes. You’ll rapidly learn that we are a long way from industry wide anything…

If power meter companies had to pass some sort of universal space grade accuracy and consistency testing protocol - a protocol that included a wide range of varying temperature and conditions. Maybe then, we could compare power numbers with high confidence.

Personally, I have found that using a well trafficked, steady climb of reasonable length, can go a long way towards helping a rider confirm at least their real world performance vs their power output.

This also means that your scale, has to be accurate. Many of these are complete junk too.

I have a friend who swapped power meters and dropped 60w. He’s into Zwift racing. It wasn’t a fun time… :joy:

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Thanks! I have considered an FAQ along the lines of “How power meters lie… let us count the ways.” :stuck_out_tongue:

But seriously, we have the repeat post of people reporting that their new power device doesn’t match their current one. Usually after minimal testing in less than ideal circumstances. Power meter type, location, setup and more are all factors.

Doing a quality comparison is more work than most people want to do, so I’ve not done more than make one real FAQ linking to some power data comparison tools. I should probably add to that and touch on the most common issues and reasons that devices might vary from each other.


Funny, I was going to suggest a heading too.

Mine was. “Your power meter is probably wrong… unless it reads high”

In that case, it’s the most accurate device created by mankind :grin: