Somebody, Anybody, Please Help Me. Massive Power Inaccuracy


TLDR; The same power metre pedals on the trainer feels ~20% harder than they do outdoors. I can understand that there may be a discrepancy between the Kickr and the pedals, but in my situation the pedals are feeling/reading ~20% harder on the trainer.

I would be forever indebted to anyone who can help me. I’m absolutely distraught- just had to abort a ramp test and I don’t know what to do. I’ve spent countless hours with TR tech and Wahoo tech (I haven’t spoken to Favero yet). Here’s the skinny.

Got the Kickr Core and signed up for TR one month ago. We couldn’t get accurate numbers between both devices, so I did a ramp test using the Kickr only. Came out to 274w. This month I thought I would do it on the pedals so outdoor and indoor power would match.

Just tried a ramp test and there was over a 60w discrepancy between the Kickr Core and my Assioma’s. I had to abort with a projected ftp of 220. When my baseline was 274w. I just can’t work out what the issue is. I know what 300w feels like on my bike outside. And it’s so far off compared to using the same pedals on the trainer it’s crazy. My outdoor numbers and times on climbs are comparable to my friends who are of similar weight. On TR I have power match on. Everything is paired and calibrated correctly. I just don’t know what to do.

For reference, I did back to back ramp tests this morning I thought I had turned the pedals off, 3/4 into the second test before I realised they were still on. I disconnected the pedals mid-workout, finished the ramp test and it came to 282w. An 8w increase from 4 weeks ago, and that’s after doing a ramp test right before, and overshooting the power on the first 6 ramps.

Is the bike you are using on the kickr the same bike you ride outdoors? First thing that comes to mind is different crank lengths that aren’t being updated, but that wouldn’t explain such a large discrepency. Maybe sounds dumb, but is there a chance that the Assioma bodies are contacting the crank arms on your indoor bike? I had to run pedal washers with mine to space them out when using them with SRAM Reds. I would think if the body is touching the pedal it would likely cause the pedals to read lower than actual.

Firstly, thank you for offering your suggestions! Same Bike. I only have one. Same crank length. Unless there’s a setting in TR or Wahoo where I need to check the crank length in their settings? but still, 20% delta for 172.5 vs 175?

Same air cooling indoors as out? Its natural for you to deliver power easier out than in if your indoor environment is causing you to overheat. I’d also forget the Kickr and just use the Assimoas as an indoors and out power source.

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First thing I would do is use either the dcrainmaker or zwiftpower tool to compare the reading of the kickr and your pedals - I wouldn’t go off the results of ramp tests.

Poor cooling indoors would definitely make it feel harder too.

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Agree with the above. Unpair your pedals from TR then do a short workout just with TR controlling the Kirk but in Resistance mode and simultaneously record the workout on your head unit using the power output from your assiomas then compare the two workouts.


Thanks for the suggestion! I have two high velocity fans, it’s actually cooler in my house than outdoors. When I’m on the devices page I can see the power readings off the Kickr and the Pedals. At 300w it was around a 60w delta. The first few rides I did on TR I struggled to finish using the pedals so I know it’s not just on the ramp test. I’ll look into the DC tool. Thanks again!

Just to be complete, when you worked with TR support did you confirm that TR is:

  • paired to the left pedal of your Assioma DUO


  • you used the Assioma app to associate the right pedal to the left pedal
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I do the above and then use the DC app or can I do it without buying a subscription? Thanks!

You can use the ZwiftPower version for free. Golden Cheetah too, if you want a bit more setup.

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Sorry, I have Uno, so no right pedal. And just to clarify, holding 260w outdoors for 40 min, no problem. holding it on the trainer, for a minute, during the ramp test, using the uno was really really tough.

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If you are on the trainer and the pedals are connected to your normal bike computer, does 260W then feel sustainable?

this ^^^ with no TR app running. Use Wahoo app to set Resistance around 35%, or Standard Mode with Level = 3.

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Good question, I’ll have to check that out. Thanks!

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OK great. I’ll give this a crack on the weekend. 2 back to back ramp tests and I’m spent. Thanks guys!

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Understandable, but in future could you not use AI FTP instead.

Yes, but I’m trying to figure out what my FTP is outdoors so I can A. do outdoor workouts and more importantly B. Have an accurate threshold reference for races.

No need IMO, if indoors and outdoors are identical your indoors and out FTP should be identical also.

It doesn’t sound like an FTP setting issue so much as some sort of connection issue preventing the number being accurate when on the trainer.

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Counterpoint, it’s all but impossible to have them “identical”. Even if you nail cooling, motivation, rider position and such, there are likely difference in flywheel vs outdoor inertia/momentum at the very least.

As we are learning, this is not something to ignore. Smart bikes are particularly unique here with their functionally fixed gearing and related flywheel speed, compared to real gearing and terrain outside. I think there is plenty at play here, and this detail is one that is worth consideration among those others.

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