Power meter differences, best practice?

Cheers.

New Xert user here, pretty new to cycling as well but not entirely.
Since late last year i have been using a Kickr V5 for indoor training and this spring i got a pair of Favero Assioma for my road bike (separate bikes indoors and outdoors because of reasons). Having a pretty weak endurance i have mostly done slow rides and added time in the saddle gingerly. Dabbled with some structured stuff on Zwift but not a lot, did the ramp test a few times and was between 200 and 210 watts. Fast forward to a couple of days ago when i tried TrainerRoad and Xert to get into a little bit of structured workouts with intensity…

After a few rides i chose Xert (obviously) and after yet another few rides (all of them outdoors, weather has been decent the last couple of weeks) i get a couple of breakthroughs and a Threshold Power of 239. I somehow doubted it, but at the same time i have been riding quite a lot this summer so i figured it might be accurate. Today i got home from work and had an indoor session planned.
Started “Where The Streets Have No Name” and eventually i gave up, free riding the last 15 minutes. It was simply too hard to make any sort of sense so i got out to the garage and took the Assiomas off the outdoor bike and got them sorted on the indoor bike. Calibrated both the pedals and my Kickr and lo and behold; Kickr says 100 Watts, Assioma says 125. No wonder Xert thought i was way fitter than Zwift’s ramp tests and no wonder the workout made me suffer almost as much as the song.

My plan is to use the Assioma app to change the power it reports by -15% (which will pretty much bring it in line with the Kickr) and set the Threshold Power in Xert manually in the account settings to ~200. I assume this value will only be temporary and change upon decay or breakthroughs? Is this a good plan or an awful plan? Why, why not? Are there any alternatives?

TL;DR: Indoors and outdoors power meters are not in sync, what to do?

Not sure I would assume Assioma pedals are wrong yet.

I have same issue with struggling to finish trainer exercise, higher pwr on Garmin V3’s (approx 5 % higher -3sec avg) than kickr. And ramp test is a crappy ftp test sorry but it is. Not designed for ftp but high jacked to accommodate lazy ass people who don’t want to suffer for 20 minutes. You will score high ftp if good sprinter, score low ftp if you are mostly endurance rider. Score just right if you are a Goldilocks all rounder

The kicker power is smoother or averaged different than your Assioma. So need to compare apples to apples

Usually when I get on my trainer I am not fresh, still recovering from hard weekend rides. So be sure u are fresh, motivated and use a fan to challenge a hard effort trainer ride

Is it possible to check with another trainer, power meter to zero in on what equipment is erroneous?

Would am option just be to use the power meter pedals on your indoor bike?

Are your crank lengths the same indoor and outdoor / did you adjust that in your bike computer? Unlikely to be 25% but could be part of it

Do you have Assioma duo or uno? Uno doubles the left leg power and if you have a big imbalance that could be a factor. Worth noting that imbalances often vary with intensity and fatigue, so scaling is unlikely to help that

Also, not sure exactly what a Kickr v5 is but have a Kickr core from a couple of years ago, and 1) you still need to regularly calibrate it via a spin down (and the trainer needs to be warm for that - I get a close match when I do that) 2) there is an option for Kickr to read power from your power meter (in case you want to only connect to the trainer, but obviously needs you to have the pedals on the indoor bike… also handy in case you want to run two apps via Bluetooth with the same power readings eg Xert and Zwift)

Would generally trust the Assiomas based on reviews and comments I’ve seen from most

Not sure I would assume Assioma pedals are wrong yet.

Oh no, on the contrary. My impression upon looking around is that the Kickr is much more prone to erroneous readings so the Assiomas are most likely the correct meters.

…lazy ass people who don’t want to suffer for 20 minutes.

I am aware of the pros and cons of the different tests, but my ramp tests and 20 minutes tests (yes, i have done both) have been pretty consistent. More importantly; when there was a reduction in Functional Threshold Power according to the tests (on the Kickr) it made sense since i hadn’t trained that much for a short while, and when i had my first breakthrough (on the Assiomas) i got surprised since i didn’t even push that hard.

The kicker power is smoother or averaged different than your Assioma. So need to compare apples to apples

Is it possible to check with another trainer, power meter to zero in on what equipment is erroneous?

I connected the Kickr to Wahoo’s own app while having the Assiomas connected to my Garmin headunit so i could see both values at the same time. Even when i was ramping up the wattages slowly (staying at the same wattage for 30 seconds or more before bumping it up) using erg mode the difference was pretty consistent. It’s as close as apples to apples i can manage probably and this is all the equipment available to me unfortunately.

And just to be clear; whether my Threshold Power is ~210 or ~240 is not important to me. What’s important is that the experience on the bikes are roughly the same and that efforts on one bike should be able to guide the planned workout thresholds for the other. And since there is no easy way (at least to my knowledge) to bump up the reported wattages from the Kickr it kind of made sense to lower the ones from the Assiomas. If i used the same bike both in- and outdoors i could simply use the pedals as a power source and if money was absolutely no issue buying a second pair of Assiomas would solve the issue but alas, those are not viable options.

Would am option just be to use the power meter pedals on your indoor bike?

Sadly, no. I use both bikes constantly during the summer season and constantly fiddling with the pedals would be too much of an hassle.

Are your crank lengths the same indoor and outdoor / did you adjust that in your bike computer?
Unlikely to be 25% but could be part of it

Adjusted in both Assiomas app and the Garmin head unit.

Do you have Assioma duo or uno? Uno doubles the left leg power and if you have a big imbalance that could be a factor. Worth noting that imbalances often vary with intensity and fatigue, so scaling is unlikely to help that

Duo, so unfortunately that shouldn’t be a problem either.

Also, not sure exactly what a Kickr v5 is but have a Kickr core from a couple of years ago, and 1) you still need to regularly calibrate it via a spin down (and the trainer needs to be warm for that - I get a close match when I do that) 2) there is an option for Kickr to read power from your power meter (in case you want to only connect to the trainer, but obviously needs you to have the pedals on the indoor bike… also handy in case you want to run two apps via Bluetooth with the same power readings eg Xert and Zwift)

They claim that the V5 doesn’t need spindowns or calibrations but i am actually planning on doing a “factory spindown” just in case.
Like i wrote to rgalisky, the power meters stays on the outdoor bike and the outdoor bike stays outside unfortunately.

Would generally trust the Assiomas based on reviews and comments I’ve seen from most

Yeah, that was my impression as well.

Ok hope the factory spindown helps… otherwise scaling the Assioma makes sense (good they have the option) and you are right, doesn’t matter which is ‘correct’ if it’s just for training… if you ever get on Zwift or ride with others in another app you may care though :wink:

if you ever get on Zwift or ride with others in another app you may care though

I do group rides every now and then, in the D and E category, but that’s just for the social aspect and always as long slow rides or recovery, so it’s all good.

I get why you are adjusting the Assioma’s as there isn’t the facility to do it on your turbo. Why manufacturers don’t put this feature in their software I don’t understand. Probably due to stopping people cheating on Zwift.
One thing to note is that your calories and carb/fat amounts will be way off if you plan to use these fields for fuelling on your rides. I’d also do a few rides at different intensities to get a better overall percentage variation.

One more thing. I can’t see if you have the Duo or Uno Assioma’s. If you got the Uno’s and a leg power imbalance this can give very inaccurate results when trying to correlate the Assioma’s with your turbo.

One thing to note is that your calories and carb/fat amounts will be way off if you plan to use these fields for fuelling on your rides.

Yeah i thought about that and while it is a bit of a bummer it’s not the end of the world to be honest.

I’d also do a few rides at different intensities to get a better overall percentage variation.

Did a factory spindown on the Kickr and was able to change the “Power scale factor” on the Assiomas to -8% rather than -15%.
After that a workout (Smart Opener 3, so a bit of everything in terms of power) came out at an average watt of 155 from the pedals and 156 from the Kickr so i call that a success. Depending on the weather-forecast i might leave the pedals on the indoor bike for a couple of more workouts just to double and triple check.

I can’t see if you have the Duo or Uno Assioma’s.

Duo.

I tried to match a single sided PM with my turbo a couple of years ago before I knew I had a large power imbalance. I spent a very frustrating few weeks trying to get it consistent before finally giving up.

If you’ve got an iPad or iPhone that runs Xert workouts on the screen for power source there is a field for altering the reported power on the turbo. It’s called Power Bias. Unfortunately this facility is not available on new Android Xert EBC app.

I tried to match a single sided PM with my turbo a couple of years ago before I knew I had a large power imbalance.

Situations like this is why the manufacturers really should make it possible to alter the power output. Who cares if someone cheats, if they want to win pixel K/QOM:s they will find a way anyways.

If you’ve got an iPad or iPhone that runs Xert workouts on the screen for power source there is a field for altering the reported power on the turbo.

Aha, that would have been splendid since i honestly believe it’s the Kickr that is at fault here. If the functionality comes to Android fine, otherwise i’ll just go ahead with my lower Threshold Power and be content that the values between in- and out-doors are consistent at least.

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