Power Meter Mess - Favero Assioma Duo

I’m writing here on Zwift as sort of a last ditch effort. I’ve tried so many other avenues and all it has led to is confusion.

I’ve been an amateur cyclist for many years. I mostly ride an M5 Carbon High Racer recumbent and sometimes ride a Mountain Bike. On my rides I almost always ride with the A group. I typically average 20+ mph for the entire ride.

As the winter months approached, I wanted to find a way to keep riding. I had less time to ride as well so an indoor option seemed like the right move. I did my research and settled on getting a Joroto Spin Bike and Favero Assioma Duo Power Meter Pedals. I figured I could use the power meter pedals indoors and outdoors and it might help me understanding more about my training.

However, here is what has happened and to Favero’s credit, they’ve been trying to figure out what the issue might be, but still can’t explain it. The power meter pedals on the spin bike result in wattage that is considerably less than any other bike.

For example, I’ve done the same test many times now. Using an average heart rate of 133 on a one-hour ride, here are the average wattage results for the ride:

  • Spin Bike - 116 watts
  • Recumbent - 206 watts
  • Mountain Bike - 209 watts

I recently did a Zwift FTP test on the spin bike and my FTP came back as 174. However, as you can see from the data above, on any other bike outdoors, I can maintain 200+ for an hour at a low heart rate. My guess is my FTP is probably closer to 230 - 250 if I did an FTP test outdoors.

If my fitness was truly at 174 then that would be fine, but first, I don’t think it is, and second, I have the outdoor rides to reflect data that it isn’t as well. Not being able to produce adequate wattage has me getting destroyed in Zwift and it doesn’t make it enjoyable. Probably the most annoying thing is how difficult it is just to stay in “E - Everyone” group rides. My heart rate will spike out at about 175 - 180 whereas everyone else is coasting along at 120 BPM. In these “E - Everyone” group rides, I still end up being almost dead last and I can forget about doing any segment sprints.

I’ll try to recall all the things we’ve tested:

  • Numerous Zero-offsets / Calibrations before every ride
  • Ensuring crank arm length is accurate
  • Changing out the crank arms on the spin bike
  • Testing with Bluetooth and ANT+
  • Testing across different platforms: Zwift, Garmin Edge 530, Rouvy, iPhone, RideWithGPS, etc.
  • Tested across different bikes: Spin, Recumbent, Road Bike

So after all these tests, the results come out completely the same over and over again. The spin bike’s are just considerably less for some reason. As I said, Favero has tried to help. I’ve sent them numerous FIT files and they’ve looked at all the data. They acknowledge that the Spin Bike results are very low compared to anything else, but they can’t explain why.

In the event anyone has seen anything like this before, please let me know. Thanks for any help.

Looking at just the watts: I am not up on the intricacies of setting up the uno vs duo on the spin bike for virtual worlds; but it looks to me just about half…and is only capturing one pedal.

Take the pedals to a bike shop that has a bike/smart trainer setup and see if you get the same type of readings. Or if you have a buddy you can try on his equipment.

You’re comparing riding a spin bike indoor with power produced outdoors? There are so many variables involved that a big difference isn’t totally out of the question.

You’ve potentially got a very different riding position, for a start.

How is the ventilation and cooling where you’re riding indoors? If you’re getting hotter then your heart is working a lot harder to cool you down. If you’re building up CO2 in an enclosed area then there’s going to be a big negative impact on your performance.

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Experimented with numerous different riding positions on the spin bike. The swings have been there, but not enough to account for the differences being seen here.

Ventilation is fine. One thing I should make clear, is that this is nothing that occurs over time. For example, if I sustain 200 watts on the spin bike in the first 30 seconds of riding, I can probably only last for about 2 - 3 minutes until my heart rate will be spiked. Conversely, I take the same power meter and connect it to an outdoor bike and ride for an hour at 200 watts. It couldn’t be attributed to cooling or ventilation.

I originally thought that too, but Cycling Dynamics from my Gamin Bike Computer shows the data on both pedals. I’ve also tried pedaling from just one pedal on both side to see what the difference might be and it appears both are reading. Favero confirmed this as well given the data they receive every time a calibration is done.

Comparing to a smart trainer setup would be good, but I’m just apprehensive about doing it right now with the pandemic. I would like to have a buddy try them out, but again, with the pandemic, I’ve been avoiding group rides, and unfortunately, I don’t know anyone else with a spin bike that could test out the power meter pedals.

What about the resistance on the spin bike - too low/high?

Something about the way you’re cranking those pedals is quite different from how you’re doing so on the road. I still think it could be your position, which can make a big difference when changed only slightly.

The resistance is adjustable on a spin bike so I can turn from 0 - 100 basically. The power meter reacts in a way I would anticipate. So more resistance yields more power at the same cadence. So it seems to react precisely, just not accurately.

I really don’t see how it could be bike fit. The mountain bike I rode on was my Son’s and my bike fit on it was really poor, but still, cranking out 200 watts was fine and even reaching 800 watt spikes were doable for just a second. On the recumbent 200 watts felt very similar, but I could only generate maybe 600 watt spikes because on a recumbent your laying down and can’t put quite as much force into the pedals. Conversely, I think the highest reading I’ve ever gotten out of the spin bike was high 300’s. It doesn’t feel like wattage is cut in half, but maybe 65% of what it should be. It is so odd.

Are you using the correct crank length, spin bikes has sorter cranks.

Yes, I’ve even changed the cranks on the spin bike. They are both 170. The new ones and the originals.

What I meant about the resistance is that psychology can come into play, and sometimes people can generate more power against higher resistance levels (or vice versa) and your resistance might be too low (or too high).

If the readings are that far out, does it feel like you’re generating a lot less power? E.g. your heart rate is peaking and you’re running out of breath, but your legs feel fine (i.e. under-used)?

Maybe you should try the faveros in UNO mode.
What I mean, install only the left pedal, and use a normal pedal on the right side.
Check ik the results are normal then.

Sort of, but more like the opposite. I feel as though I’m putting in more power on the spin bike, but the resulting watts are coming back less. For example, if I jump on the bike and go to 200 watts on the spin bike and hold it there, I can only last 2 - 3 minutes, maybe. My heart rate will spike out and I have nothing left. It is a really big struggle to hold 200 watts on the spin bike. Conversely, on any bike outdoors, 200 watts is not tapping me out and as a matter of fact, I can hold it for over an hour.

Sorry, I forgot to mention that I have done this. All the results came back basically identical with the spin bike reading much lower wattage results when compared to any other bike outdoors. It is so odd.

The spin bike has no coasting right? It’s basically a fixed gear except your are pushing a huge flywheel. No shifting either and no gears.
Personally, I really can’t see how you can compare a spin bike to a road bike on a trainer. There are just too many variables. If you want to rule out the pedals either you ride them on a road bike on a trainer or have someone you know ride them, calibrate them and see if the pedals are performing normally. Right now you’re chasing too many variable. Just my opinion.

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You stated the resistance on the spin bike is 1-100.
Where do you tend to set it?
If the spin bike has a large fly wheel, once it gets up to speed, it won’t take as much power to keep it moving.

Correct, the spin bike does not have any coasting. I’m not sure there are so many variables. Spin bikes are used by probably at least 1000’s of people on Zwift without issues. Many of them use crank-based power meters or pedal-based power meters to ensure power is accurate. Their videos on YouTube is sort of what led me to do the same. The power-based power meter pedals would ensure I wasn’t cheating on Zwift and that my power should be accurate, but it has sort of gone in the other direction where I’m pretty confident the power meter readings are way too low, but only on the spin bike, which is confusing when so many others are getting accurate results between their road bikes outside and their spin bikes.

Here is a good example on YouTube where some above average riders are testing the Peloton Bike+ against the Favero Assioma Pedals. The Peloton would have a huge flywheel and is really just a spin bike. The results aren’t spot-on between the two, but much closer than what I’m seeing.

Correction: I can’t include links in my posts. It might be because I’m too new or they just don’t allow them here on Zwift Forums. Anyway, if you want to see the video, the title is " How Accurate is the Peloton?? Power test!!" and the creator is “Biller Bike Reviews.”

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It depends on the ride on where I might set the resistance. Some rides I might just want to do some low heart rate work / steady state so I might keep the resistance at about 50%. This keeps my watts at around 130 and my heart rate will be around 133 (on average over the hour or so). If I do a ride where a workout is involved then I’m forced to adjust the resistance to meet the power output that Zwift says I need to be riding. So if they say 200 watts at 90 rpm then I’m cranking the resistance up a bit. If they say 105 watts at 85 rpm then I’m cranking it down to get there.

Recently, I did a Zwift FTP Ramp Test to see what it might think my FTP is. It came out to be 174. Again, it feels like a low number on the spin bike when I can go do low heart rate work outside on any bike and at an average heart of 133 over the course of an hour, put out 206 watts. I haven’t done an FTP test outdoors on my bike, but I’m willing to bet the result would be considerably higher than 174. If I had to hazard a guess based on the power readings I’m getting outdoors, I would think it might be 230 or maybe a shade higher. Those numbers give you an idea of the discrepancy I’m seeing when others don’t seem to be.

Ultimately, I know all this is confusing and I appreciate everyone’s attempt to help. My intent posting here was just on the outside chance that someone was seeing the same thing I was, but I’m getting the sense that isn’t the case. Favero has said the same thing and they concede something is not right based on the data they are seeing, but the can’t explain what the root cause might be. They have offered to take the pedals bike and conduct more testing on them in Italy so I might go that route. Otherwise, I might just continue to train with them and look for an opening to test against something like a Kickr Core or a Kickr Bike. I think that would help answer a lot of questions for me, but I think I’ll be waiting until this Pandemic subsides some. I just don’t think this is worth it to take the risk right now. All the best.

If Favero is offering to swap them out…I would accept that offer.

I would suspect the variable resistance as the root cause.

It does not make sense, power is power. I don’t think it has anything to do with the pedals. The only difference to the pedals is the way the resistance is applied.

When you are on the spin bike I would think you don’t have the resistance set to the same level. You may be higher cadence on the spin bike.

I installed a stages left crank on my wife’s spin bike and I can do the same power on her bike as on my Saris H3 or my Powertap wheels.