What happens with AT using a different power meter outdoors?

What happens with AT and progression levels when we have a different power meter outdoors that reads higher than our indoor pm/trainer?

To do outdoor workouts in that case we have to set our FTP higher before syncing the outdoor workout. Changing FTP now changes progression levels, affects AT, and I assume affects the new AI FTP detection. I guess when we change FTP from indoor to outdoor to indoor hopefully the progression levels end up back at the same place? In between that change will AT try to change future workouts for the lower progression levels that result when FTP is set higher? There’s been a feature request for a long time to have multiple FTP settings, seems like that might be necessary for any of the new features to work effectively. Or am I missing something.

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Are you using a smart trainer for indoors? If so - there shouldnt be a large difference between them (within 3-5% with smart trainers usually claiming up to 2% or 3% and decent powermeters ±1,5%) or otherwise, one of your devices is not calibrated or zero-offsetted correctly.

You can do dual recordings of the same ride (one file coming from smarttrainer, the other from powermeter) and match those to see if there is a difference.

It sounds like your primary concern is that the benchmark for your workout difficulties, your FTP, will vary between indoor and ourdoor setups.

The GOOD NEWS is that with AI FTP detection, we address this!

From ‘How To Use FTP Detection’

I use a different power meter for my outdoor rides than for my indoor rides. How will FTP Prediction handle any differences between my two power meters?

This is one of the benefits of using a model as opposed to using an estimate. We don’t simply estimate your FTP based on outdoor power data (which is often reads higher than indoors). Instead, we include your outdoor power data in addition to the various data points we already have to predict what FTP you’re likely able to achieve as a result of the Ramp Test.


For this statement “Instead, we include your outdoor power data in addition to the various data points we already have to predict what FTP you’re likely able to achieve as a result of the Ramp Test.” I’m interpreting that the predicted FTP is for your indoor setup then and somehow its recognizing the offset difference of outdoor rides.

Less looking at the specific differences of inside v. outside, more looking at the full scope of your workouts and activities to create the most comprehensive/accurate FTP.

I have a tacx neo measuring at the rear wheel output indoors vs stages crank power meter outdoors. So at the least there is the drivetrain loss due to the different locations.

Based on 5 years of rides and races I’ve settled on 25w greater for outdoor vs indoor which theoretically is comprised of:

  1. Different measurement location, drivetrain around 3% loss maybe 10w
  2. Different power measurement device from different manufacturer
  3. Difference in physical capability, cooling would be the main contributor here, possibly this is contributing 0 watts of the total difference, its been debating a lot both ways on this forum.

It’s possible to eliminate this difference by using one of my outdoor bikes on the trainer and using power match but who wants to switch a bike on and off the trainer constantly. Easier to just change the offset number since its defined. I also feel like the tacx neo works better without using powermatch so want to use that reading, but thats just opinion and doesn’t matter to the main issue.

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I’m not worried about FTP prediction since that’s just a suggestion. More just wondering if AT is going to suggest adaptations to the plan when my progression levels drop from changing FTP setting 25 watts higher to do an outdoor ride.