Tacx Flux erg mode oscillations

Hi people,

I’m using Trainerroad with both a Tacx Flux and a Tacx Neo.
When I’m using my Flux, I’ve observed that there seems to be some difficulty with holding a given wattage. Here’s an example from last night


If you zoom in on the intervals, you can see that the wattage shoots over/under by as much as 25w, however, the average power seems to be in the correct range.

I’m wondering if there are some clever regulation-algorithms within the Trainerroad app that causes it to oscillate so much?
When I’m riding with my Flux in Zwift, the variance is much smaller, typically +/-5w.
In the example, I’m doing my intervals at around 280-290w, with a 95-100 cadence in the 36/21 or 36/19 gear, using the iPhone app.

Any ideas whats going on and how to stabilize it?

Kind regards, Rune

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What smoothing setting do you have within the TR app? it could be down to that.

I have it set to 7s, but doesn’t that only affect the numbers and the red/green bars displayed in the app ?
It is my impression that the graph is drawn with the “raw” data from the Flux, which I assume is sent in 1s intervals.

Hey there!

These oscillations are due to the fact that your pedal stroke is not perfectly smooth in reality, and that is picked up on some trainers more than others. In other words, some trainers apply a smoothing factor to the data before they send it to us. This causes the graph and all the data we receive to be pre-smoothed.

We do not have a way to smooth the data that is charted on the graph at this time. TrainerRoad power smoothing only effects the Power readout and not the graph itself. Zwift likely allows for smoothing of the graphed data after it is received, which is why you see less oscillation on their platform.

At the end of the day, the oscillating power graph is more realistic and gives you some insight into the smoothness of your power stroke and your ability to maintain constant power. The more you focus on smoothing your pedal stroke, the less the Flux will oscillate, and the more efficient you will be at putting power to the pedals :+1:


Just a quick update.
A member of the Tacx Flux owner-group on Facebook suggested using a taller gear, as it was his experience that it stabilized the oscillations.
And behold, last night I tried it in the 36/18 gear instead, and the oscillations were as good as gone.
I’m thinking the Flux might have problems with low flywheel-speeds, so a taller gear will bring higher speeds and more controlled resistance.
The only downside is that I have to switch a few gears lower in the rest-segments between intervals, or else i’m hitting the “wattage floor” of the trainer with my preferred cadence.


Yup, it’s a common issue on the mid and low cost trainers, unfortunately.

I wish they would all document and publish the info, so buyers could compare units and know what they need to do when they start using them.

have you solved the issue?