Tacx flux maximum incline

Hi, I have a Tacx Flux since smart 2020. I always thought that the max incline of the Flux was 7% as this was my experience with it. Looking to buy a new trainer (and I will probably try to sell that one), I saw in the specs that the max incline is in fact 10%.

I understand that the advertised max incline is for a typical rider weight. I read values somewhere of 75kg, with maybe 10kg extra for the bike (last point not clear). As I’m myself weighting 72kg, it should be ok.

I have made some tests with the Tacx app, Rouvy and Wahoo RGT, all on Android if that matters.

My weight setting are the following:

Tacx and Wahoo: Rider weight = 72kg

Rouvy: Rider weight = 72kg, bike weight =7,5 kg.

Also, reality is set to 100%.

The test is as follows:

- Choose a fixed gear ratio, as for instance 34x25.

- Keep the cadence constant (between 70 and 75 rpm).

- Have a look at the power output.

I expect that the power output increases till the limit of the trainer.

Results in the three apps are more or less the same:

Slope less or equal to 2%: 65W
3%:100W
4%:130W
5%:150W
6%:170W
7% or more:190W
So it confirms my impression that the resistance doesn’t increase above 7%. Is this expected behaviour? If not, is there something I can do about it? (trainer is already calibrated via the Tacx app, firmware is up to date).
If this is expected behaviour, does that mean that it will be the same if I upgrade to a Tacx Flux S, which also claims a max incline of 10%?
Thanks a lot.
  • if I upgrade to a Tacx Flux S

    What is the point of such an upgrade?

    Flux and Flux S differ only in this:
    https://support.garmin.com/en-US/?faq=4uJKacGgTT8oRLMLYk18F7

  • Yes, I agree, that was more a rhetorical question. As said, I first thought that the max incline of the Tacx Flux was 7%, so why not go to 10% with the Flux S. But specs are the same, so my question remains, is what I see the expected behaviour or is there an issue with my Flux?

  • I read values somewhere of 75kg, with maybe 10kg extra for the bike (last point not clear).

    Test the hypothesis that 75kg is the total weight including the weight of the bike. Set the rider weight to low and repeat your experiment.

  • I believe I found the reason. Tacx is just playing with the numbers to show this value of max incline.

    You can find this info on the Garmin site:

    All Tacx bike trainers are spec'd with a maximum incline value. This value is calculated with a body weight of 143 lbs (65 kg) in reference to the "strength" of the resistance unit when cycling 6 mph (10 km/h).

    No words about the bike weight, but at this point, let's suppose that 65kg is for the combo bike+cyclist. The Tacx Flux has a maximum torque of 22Nm. This is at least a value independent of the weight. So, let's use  this site to calculate the power needed to climb 10% at 6mph (9.65 km/h), that gives us 185W.

    Taking a circumference of 2.11 m, this speed is achieved if the wheel rotate at 8 rad/s, and so the torque is 185/8=23Nm, not far away from the 22 in the specs.

    In my tests, I see a max torque of the Tacx Flux equal at 21Nm. And so, if I take a total weight of 80kg:

    With a cadence of 75, and a gear ratio of 34x25, this gives a speed of ~12.9km/h. At a grade of 7%, this gives a power of 220W and a torque of 22Nm.

    And so, there is my limit. Conclusion, my Tacx is working good, the advertised maximum incline is for really light riders and it is much more reliable to look at the maximum torque.