Power Meter Change: Adjust previous workout power data

Is there a way of adjusting up or down previous workout power data?

I’ve finally invested in a power meter which is now driving the power data on my Tacx flow trainer and on any outdoor rides. The issue is the Tacx was overestimating my power by around 25w (checked by disabling power match on 3x20’s).

So, despite my ‘trainer-collected’ FTP being at an all time high, all my new PR data and FTP scores are now (depressingly) 25w lower than all my old rides because the data is coming from the power meter.

Is there a way of taking all my old workouts and dropping their power data by 25w? And if not, can this be added as a feature please? I’m sure there are many others that have changed from VP / smart trainer / between power meters and are having similar issues.

Thanks all!


You might be able to do it piecemeal (one at a time) in fitefileTools.com

Just ignore your old numbers as you can’t go back and change the data from a number you think might be correct. Just an example but the Tacx trainer ‘might’ be more accurate at lower wattages, than higher, so just knocking 25 watts off everything won’t work.

… and create a new “season” in TR starting now so that your PRs for this power meter can be acknowledged and hopefully motivating.

1 Like

This would be a big big code and lots of resources, don’t think that will be on our roadmap anytime soon, and apologies for not having a fix for that right now. :pensive:

Thanks for all of the helpful, and extremely rapid, responses!

Out of interest, if I manually replace my FTP history to be in line with the PM, will that mess up any of the data around that time, or am I safe to do that?

Just curious, what powermeter did you buy? I also have a Tacx Flow, and just bought the Favero Assioma Duos, but I have the exact opposite problem as you do: my assiomas are reading about 20W higher than the Tacx Flow. That’s so weird.

Why not just leave your old FTP as +25w as per the Tacx Flow numbers, and then have your new one from your most recent FTP test since you got the PM? Can appreciate it will be annoying in terms of comparing power PRs, but all your TSS, chronic training load (fitness on strava) will be correct. If you change your historic FTP for those Tacx Flow measured rides, then your TSS will be artificially high.

Powertap P1’s. I guess the tacx force curve will vary depending on many factors (tyre pressure, tyre to trainer pressure, tyre grip/resistance, calibration etc.) whereas the direct force power meters should be relatively accurate to each other?

Yeah I think you’re right, it’s going to mess with too many things.

I’ll just have to put my adjusted FTP’s in a word document, print them out and stick them up somewhere for motivational purposes!

Many thanks all, very cathartic!


Ok not to worry @IvyAudrain - thought I’d ask in case it was a simple fix!

1 Like