Should power be higher at pedal or trainer?

I am riding a Neo indoors and I’ve added the Assioma/Xpedo pedals. They track well, but the pedals are consistently reading about 2-5% lower than the Neo. I’m not surprised that they are a little different, but I guess I thought the pedals would be the ones reading higher, not the Neo, simply because I have direct contact with the pedals.

Am I thinking about that wrong? Should the pedals be the one with the lower reading?

I can’t just switch and use power match with the pedals because long term they will be on my gravel bike, not the trainer.

My Vector 3 and my Neo OG are within less than 1% of each other.

Pedal should read higher, but should be closer than that though (assuming both have a 1% +/- accuracy).

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Did you check your crank lenght?

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You are correct. Something isn’t quite right! :smiley: Check your pedal setup…make sure you have selected the correct crank arm length.

I just went through the process of checking several different drive train setups & comparing pedal-based power to hub-based power. The difference between a road bike with 175 cranks and a tri bike with 165 cranks is VERY BIG is you just leave the pedals set to the default crank arm length.

Nominally you should expect to see 4W to 9W more power at the pedals than at the rear hub. That’s for a fairly well lubed 10sp or 11sp setup. 9sp is quite a bit worse. If you see higher power at the hub, something is screwed up. If you see no power difference…patent that lube!

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Yes. Crank length was set properly and calibration of the pedals was done.

Of course now the question is which one is right? :joy:

Thanks for the feedback everyone. Sounds like the pedals should be higher. I guess the easiest solution is to adjust the pedal output up to the trainer so I’m working from one constant ftp indoors and out. I realize that may skew my outdoor output high, but really it’s just about consistency for training targets. Right?

I happen to have Assioma Duos and a Neo 2T. They are within 1% of each other for average power over a workout or interval. However the Assiomas are more spikey which is what you would expect from a pedal based measurement.

Are you seeing a 2-5% difference in average power or is that your observations looking at the measurements in real time?

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Both. It’s almost ALWAYS lower in the moment, even when OOS, and definitely lower overall.

I would guess that the Neo is the one giving you inflated power readings. Trainer manufacturers always seem to skimp on power accuracy.

Yeah, don’t adjust anything just trust pedals and go with them from now on. Pedals use strain gauge versus trainer that basically estimates your power albeit it’s all very close but I’d trust pedals over a trainer.

I will share my experience with current power meter tests…
I have started off with Shimano Dura Ace Right Side system and doubted the numbers a little bit thinking they were too low. Also tests from GPLama/DC Rainmaker suggest the right side is reading low on the new shimano cranksets.

I compared it to NEO (also Elite Direto that was totally wrong until belt tension was changed) and it has reported about 3% more on average.
I have now bought a set of Assiomas and they are tracking within 1% to my Stages, that I thought would be under reading. Also, the higher the power the more my L/R balance shifts to 51/49 and therefore Stages reports less as it is a right only measurement. So, my doubts were correct but now I see a clearer image.
So, yes, from the tests it seemed that NEO was reading higher than the other two systems, but since assiomas are used as a benchmark by the reviewers I trust them 100%.

Also, make sure you change the crank length in the garmin/wahoo not on the actual app as the garmin overwrites the favero app.

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That’s not an option since the pedals will be used on the gravel bike, not on the trainer.

This is a good point. I had not thought of that. I made the adjustment in the Favero app. Will have to see what I had on the Roam.

Yes, I’ve learnt this by making the mistake too! Changing the length by 2.5mm gives +/- 1.5-2w or so.

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I’d say thinking about it at all is wrong. Why does it matter if they’re different? You should stick to the same measuring device.

If they were calibrated identically and were somehow identical units then you would expect drivetrain losses with the turbo but since they’re not, comparing the 2 numbers is a waste of time.

Just stick with the numbers that your trainer gives you.

Because I use TrainerRoad indoors and out.

Then do an FTP test indoors with your indoor measurement device and outdoors with your outdoor measuring device. Comparing 2 different measurement tools is a waste of your training time.

How do I set two different FTP’s in TrainerRoad then?

You don’t.

Let’s say you have a 200w ftp outdoors and a 180w ftp indoors. Set your FTP in TR to, for example, 200w which will be perfect for your outdoor workouts. Then whenever you do a workout indoors, manually adjust the intensity at the beginning of the workout to 90%.