Why are Tacx trainers suddenly boosting your power? – and how to fix it

Edit: The problem was fixed in Zwift version 1.0.6541 released 2021-03-23


With the update Wednesday to game version 1.0.64913 many – like really many – have suddenly experienced crazy power numbers when using one of these trainers:

  • Tacx Boost
  • Tacx Booster
  • Tacx Blue Matic
  • Tacx Blue Motion

The problem is not with your speed sensor, nor the trainer itself, but Zwift introduced a bug. It changed the power curve which is defined in-game and used to translate speed to power.

We’ll have to wait for Zwift to fix it for real but in the meantime you can get riding with realistic number simply by selecting a different trainer model from the list in the pairing screen.

I dug into the defined power curves and found what seems to be fairly close matches:

  • Choose Jetblack M5 Mag Pro instead of Tacx Boost
  • Choose Tacx Blue Twist instead of Tacx Booster
  • Choose Jetblack M5 Mag Pro instead of Tacx Blue Matic
  • Choose Minoura MagRide-60 instead Tacx Blue Motion

Simply choose the alternative trainer instead of your Tacx when pairing (but remember to let the trainer resistance setting be the same as always for your Tacx – simply ignore what Zwift says it should be for the alternative trainer).

Here are the power curves so you can see how they compare. The graphs show power (watt) as a function of speed (mph) – how much power Zwift calculates you are putting into the pedals based on the speed of your rear wheel:

Tacx Boost vs. JetBlack M5 Mag Pro
Tacx Booster vs. Tacx Blue Twist
Tacx Blue Matic vs. Jetblack M5 Mag Pro
Tacx Blue Motion vs. Minoura MagRide-60

7 comments

  1. Thank you, to day I was banned for doing over 800 watts. I wait for the final solution.

    Regards

  2. Ever since the update, I have only been able to connect my tacx trainer but no watts showing up, it just says “no signal.” Nothing seems to work.

  3. I got my 700w 800w and 900w badges today thanks to the glitch.

    Thanks for the solution.

  4. Thanx Jesper,
    unfortunately I noticed your article after the update. With your help, I could understand what happened during about 1 week, where I saw power numbers that before and after has never been reached. So far so good … but … in this week, zwift changed my ftp to unrealistic value.
    Do you have an idea how to bring it back to real = lower value?

    Kind Regards from Germany

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