Help! vast difference between two indoor training environments

I have noticed a big difference between power on my SB20, and my Favero Assioma duo Pedals. At first I just chalked this up to heat problems with indoor and outdoor rides. All that changed this week. I put my favero pedals on a dumb spinning bike at work, so that I could do workouts there during lunch, and then also complete workouts at home on the SB20. Yesterday, I did an indoor workout on the SB20, and couldn’t complete it. 1 hour in, my average power was only 189 watts on an endurance workout (virginia). Then today, I hop onto the dumb bike at work with the favero pedals as a power source, and suddenly, I easily pop out a 1.5 hour workout with an average power of 245 watts (this was on Andrews, another endurance workout). I’d like to think the Favero pedals are right (for obvious reasons) I did race LOTOJA recently, and performed well enough that I think my favero numbers (which would put me at over 4 watts per kg) were right. Is there a really good way to test both systems and see which is right, and then hopefully find a way to adjust them to match? I’ve seen people hanging weights from pedals, but I’m not sure if that would work, or what software I would use to do such a test.

Sadly, you have taken the red pill, and there is no going back :slight_smile:

Here is what I would suggest based on going through something similar.

  • Start using the Favero app to zero your pedals. This sends some telemetry back to Favero, so if you end up needing to contact support they can use this to get more insight into what is going on with your pedals.
  • You need to record the favero’s on a device that records L/R data (such as garmin, etc), and compare that to a separate recording of the same workout from the SB20. DRrainmaker’s analyzer can do that, golden cheetah, or I think zwiftpower can also do this.
    ** Since each pedal is an independent power meter, if both pedals agree and the SB20 is different that strongly points to the SB20.
  • You can easily do the static weight test with the Faveros to at least check for relative calibration. You don’t need an accurate weight for this, just something in the range they recommend. You do the calibration on each pedal, and cancel before changing any settings. You should get close to the same value on each pedal if things are working. (I have done this myself and it is straightforward.)

The real problem is that unless you find something like 1 pedal being way off, or Favero identifying a problem from the telemetry data you will be in the position of trying to get either favero or Stages to admit their product is broken based on your testing. Expect a lot of finger pointing and excuses at this point. Also you will hear lots of suggestions for powermatch, as this is the problem it is meant to solve, even though its whole purpose is to paper over all the problems about power meter and smart trainer accuracy.

The other things to check are:

  • Are your SB20 + pedals on the latest firmware?
  • Are the battery levels in both pedals “high enough” for the system? I’ve seen in the past if one of the pedal batteries gets very low, the effort level on my SB20 is divorced from the power it displays. That is, the SB20 could be saying I’m doing 200 watts, but it feels like 240 / 250 watts.
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One more thing, is the crank length the same on both bikes? This will influence the reading as well.

Okay, apparently this low battery thing was the problem. Both power meters would run and zero, but the battery levels were low. I swapped the batteries, zeroed again, and things felt great! I still might do a little comparison project to see how different the favero pedals are from the stages power meters. Thanks everyone!!!

This low battery thing is concerning. Is there a point when it suddenly crops up, it does it slowly decay the accuracy? Either way, it isn’t the greatest. I’m hoping stages can make changes to fix this problem.

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Sorry to distract from OP but just about to buy assioma duo pedals (currently have 4iiii left arm crank PM which been happy with but want double sided PM).

All reviews seen been v good, everyone been happy with assioma?

I love them. I’ve never had a single problem, and I’ve used them a lot. They charge super easily, always connect to my wahoo elemnt, and they auto zero. I just connect the charger after each ride, and enjoy all the benefits you hope to get out of a power meter.

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From my experience, it feels like it is a “cliff” type effect. That is: everything is fine, and then the batteries hit some level at which the effort diverges from the power reading

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The other flag I’ve experienced for low battery is it taking longer than normal for the workout to start - I have auto start / stop on pedaling turned on.

I had some weird calibration numbers recently on my Stages and the battery wasn’t even low. As a last ditch effort, I swapped batteries and it started calibrating correctly again.

My solution is to buy fresh, high quality batteries for my Stages going forward. No more 20 packs of inexpensive no-name batteries. My guess is that a battery could be putting out less than optimal voltage. It still works but not well. I’ve had what I think is a similar issue with rechargeable AA batteries. They put out 1.2v, not the 1.5v that you get from a fresh alkaline battery. Most things work fine at 1.2v but a few pieces of electronics can’t tolerate the voltage difference.

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