Favero Assioma Pro RS-1: bad power readings

Tech Tech Help
1

Hi all,

I recently bought a pair of FaveroAssioma Pro RS-1 power meter pedals (the new one-sided road versions of the Pro MX-1/2) and after installing them per the instructions and doing several indoor and outdoor rides, I found the power readings to be consistently +\- 30W low. I contacted Favero support and followed all of their instructions, sent power files, etc. and eventually they sent me a new spindle. I swapped in the new spindle and just did a quick ride on my trainer and I’m having the exact same issue: reading about 30W low.

The problem is less present below 100W but on a test ride this morning, at 150W on my smart trainer (Elite Direto, which is consistent with my other power meters and my perceived effort), the pedals read around 120W, at 250 it was around 220 and at 310 it was around 280. Those values are of course approximate since they are just what I was seeing in real time as I rode and there are differences in where they are measured, data processing, etc. I did be sure to ride at each of these power levels for at least 20 seconds to make sure any smoothing effects had time to work through to a steady state. I recorded power files from each for a more precise comparison for Favero. What is probably most relevant is that it doesn’t seem like it is a linear error where it is X% off. If it were, the 30W at 150 would be 60W at 300 and it doesn’t appear that way. I have been riding with various power meters and smart trainers for 10 years, so I’m pretty familiar with using them and how they track with my perceived effort.

I have already done the following:

  • confirmed my actual crank length matches the crank length displayed on my bike computer and on the Favero app

  • Eliminated nearby Bluetooth signals

  • Confirmed that the pedal was installed to the specified torque (although I will admit to having a pretty low-quality torque wrench, so it may be more fair to say approximately the specified torque… that said, I have uninstalled and reinstalled them a few times so the torque is probably different each time but the problem is the same)

  • Confirmed that the firmware on the pedals and on my computer (Garmin Edge 840) is up to date

  • Installed the pedals on a different bike and ran through the testing on that bike

  • Calibrated the pedals with the Favero app before each ride/test. I also used the calibration command on my Garmin for a few tests as well

It is worth noting that I am aware from prior two-sided power meters that I have a small imbalance (51/49) with a weaker left leg and this is a left side only power meter, but my trainer is direct drive and my other currently-functioning power meter that I use regularly is right side only, so if the issue were an imbalance, the right side power meter would be reading high at a similar magnitude and it is not. It is consistent with the power from the smart trainer. Also, the imbalance would have to be much larger than 1-2% to create this kind of effect.

I’ll uninstall and reinstall the pedals this weekend and test again, but I’m pretty well out of ideas. It seems incredibly unlikely that I would get two power meters with the same problem unless lots of other people are having the problem as well from a bad batch. My understanding is that these are the same spindles from the SPD style pedals that have been out for a year and get outstanding reviews, so it doesn’t feel like I’m an unfortunate Guinea pig.

Has anyone else had or heard of issues like this? Any suggestions for what to try? I really don’t want to have to send these back, but a power meter pedal that doesn’t read power correctly is just a heavy, expensive pedal.

Thanks!

Matt B

2

As an owner of the Direto I would never trust its values.

Do you have a spider/crank based power meter on one of your bikes that you can test the Assioma against?

3

As a diagnostic step, I’d connect the pedals to a device with a different technology stack. A smartphone with the Cadence app would fit the bill. If the power values are still too low, the problem is completely on the Favero side. But if you start to see realistic numbers, there might be a software problem between the pedals and the Garmin.

Separately, you might be able to minimize the error by deliberately fudging the crank length (since you have other power meters to test against). This isn’t ideal; but it’s something to consider.

4

I do, and I’m going to give that a spin, but the direto is pretty consistent with my other power meters in general terms. It is certainly closer to reality than the faveros at the moment, so it’s just serving as a reference point rather than ultimate truth. I also took them out and rode a 30 minute climb at threshold (something I’ve done on that climb dozens of times) and it was also clear from that test that the pedals were 30ish watts low, consistent (enough) with the direto.

5

I’ll give that a try. I did read the power through the Favero app and it tracked with the Garmin, but have not tried a third party app.

6

Oh, and on fudging with the crank length, I messed around a little bit with that just to make sure I wasn’t getting the crank length wrong and it didn’t really change much with a small (2.5mm) change. Maybe a big fudge would help (there’s also a % adjustment in the app) although since it doesn’t seem to be a linear error, it seems that fudge-fixes might only work well enough within a fairly narrow power band. And there’s also the “I paid $600 for this, it should work” element…

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7

You may already have ruled this out, but I just thought I’d check if you may have a significant left-right power imbalance.

8

The Favero app also has a static weight test buried in some diagnostic settings that you can try with a known mass like a dumbbell. If that reads correct then the error is likely not in hardware

9

An update on my Favero pedal saga: Favero sent me a new spindle that I swapped in per their instructions. The problem persists. 30-40w low readings at almost any power above about 120W. Even at 500W it is still 30-40w low, so not a linear error. I tried it on my trainer and then installed the pedals on my gravel bike which has a right-side only Stages power meter. Same error at the same magnitude across two alternative power sources and three bikes.

Here is the new twist: on today’s ride I did a 5 minute effort at about 290W on the known power meter (read at about 260 on the Faveros). Near the end of the effort, I stood for about 15-20 seconds and while I was standing, both power meters were reading about 310W. When I sat back down, the Favero reading dropped back to 30-40W low. I stood a few more times and the same thing seemed to happen: while standing, the Favero readings were higher and in line with (if not above) the Stages readings. I probably didn’t notice this with the first spindle because all of my tests were on the trainer and I rarely stand on the trainer. I have emailed Favero with this update and the power files. We’ll see what they say. Not sure if that additional information sparks any ideas among the bright minds here in the EC community.

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