ERG Mode and Tacx Flux S, Power2Max, controlling with lower wattage


I am using the following equipment:

  • TACX Flux S,
  • Power2Max Powermeter
  • Win 10-Laptop with an Ant±Dongle and an USB extension-cable (Dongle is placed right next to the trainer).
  • Most of the workouts I am doing with the smaller ring in front (34) and about 23-25-27-30 at the back.

I have the following issue:

During a SST-Training the software seems to have a problem, when the wattage is dropping from, for example, 190 watt (sst-intervall) to a cool-down-part with about 85 watt. The wattage drops, but it only drops to about 110/120 watt. Now, when I am switching from ERG-Mode to RESISTANCE-Mode and back to ERG-Mode manually, everything is fine. Now the software addresses the 85 watt and the trainer can “hold” them.

From my point of view it is not related to the “wattage-floor” of the trainer, because if I am switching between the modes manually, everything is fine. All the time my cadence is between 85 and 95.

Today I did another test (same gear-set: front 34, rear 27):

  • Warm up for 5 minutes with 85 watt (85 cadence): Everything is fine, the software addresses the wattage and the trainer can hold the 85 watt.

  • 10 Minutes intervall with 195 watt (85 cadence): Everything is fine

  • 5 Minutes cool-down with 85 watt (85 cadence): Now it happens, the wattage drops only to about 120 watt. Now shifted from 27 to 30 (rear), the wattage decreased a little bit to about 105 watt. But the wattage did not decrease to the 85 watt. --> Now I switched to RESTIANCE-Mode and back to ERG-Mode manually. The everything was fine, the software addressed 85 watt and the trainer did id as well.

Right after this, I did similar tests with Zwift. And I did not have any issues like this with Zwift.

For me it looks like, that trainerroad (in combination with the TACX FLUX S) has an ERG-Issue.

Do you have any ideas, what I can do (it is a pain to switch permanently the mode during a SST-Training g).

Best regards


I feel your pain. I bought the Tacx Flux on offer not so long ago. One if my gripes was the high wattage floor.

I guess the S is a newer version so it’s strange the wattage floor changes between intervals. Mine was around 120-130 in the middle of the block. Always had to change down.


Well, I think it is not related to the wattage-floor, because at the beginning of a workout the 85 watts are hold perfectly. And during a workout, if I switch between the modes manually, the 85 watt are held perfectly as well.

It is only an issue, if I do not switch manually.

Maybe it is related to the wattage-floor in combination with the temperature of the device (because mostly the issue occurs after a time-period and never at the beginning of a workout).

BUT on the other hand, the question is, why does this not happen with Zwift?

Best regards


have you solved the issue?

I’m new with TR and I’ve been looking for information on this subject

I have the Tacx Flux S and the 4iiii crank and I have the same feeling

I have used ERG with Zwift and The Sufferfest and it had not happened to me

The rest interval never gets you down to the marked area

Any suggestions?

I answer to myself

I have already read several forum posts and blog articles about this. I am clear about the advantages and limitations of the ERG and the roller.

And this also clarifies many things