Gradient Tacx Flux (T2900)

Dear all,

Being a recreational triathlete who loves riding outside, my partner was so amazing as to buy me a Tacx Flux as a birthday gift. So far I’ve been using it regularly during the week: sometimes for FTP tests (now at around 287W), more often for pre-breakfast rides to improve my anatomical system’s fat burning.

During the first two months I used the Tacx riding app, because, well… it came free with the trainer. After the 60 days were past, I switched to Zwift by recommendation of a friend.

My problem: the trainer, which supposedly is able to imitate 15% gradient, doesn’t seem to reduce or increase resistance during Zwifting.

Here some details:

  • Trainer is regularly calibrated through Tacx app
  • Also connected: Viiiiva HR monitor (for Bluetooth pairing) and (think this might be important!?) my Garmin Forerunner 945 (for Training Effect measurement)
  • Typically I run Zwift on an iPad or iPhone XR
  • During training rides, ERG mode is on because I ride on Wattage
  • During ‘Free rides’ ERG mode is off (correct?)

What I do notice when I am cycling uphill, my average speed goes down, as it goes up while cycling downhill. However I am not really interested in my average speed, I am interested in utilizing the trainer’s capacity to imitate riding uphill. It really doesn’t get heavier.

Very much looking forward to some help!

Either it does not register as a “controllable” trainer, or “trainer difficulty” is set to “off”.

Care to share you device pairing screen and in-game setting?

Two probable reasons.

  1. The trainer is not paired as an FEC device. FEC is an ANT+ extension that allows the trainer to be controlled by a third party application.
  2. The trainer is in ERG mode. ERG is a mode that removes simulated control in relation to terrain. This needs to be switched off.

Also ensure that your trainer difficulty is set correctly (100%) is always the go to level!

I own a Flix and i would bet on the FEC issue. Ensure when you pair the trainer FEC is in the name of the device.

The iphone ans I pad use Bluetooth so there is no option for FEC.

@Vincent_Willem:
Make sure that your trainer is not connected to the Tacx app. I would try uninstalling tacx app just to be sure.
In the paring screen you need to pair as Power source and controllable.

You said “During training rides, ERG mode is on because I ride on Wattage” does erg mode work? As in, does it change resistance to keep you at the desired wattage during a workout?

If so it suggests zwift is controlling the trainer.

Hi B_CN,

Don’t think the difficulty was set to off. Herewith the screens.image0 image1 image2

Indeed FEC I’ve never seen appear anywhere.

So the Tacx app I’m referring to is Tacx Utility. It doesn’t pair to the device instantly when I connect the trainer, I think (because I don’t open the Tacx app on my phone, hence it’s not active). Although it might connect to the Bluetooth of my iPhone by default. Shall try and disconnect that.

So when I train on Wattage, ERG works. When it moves to a different part of the training, resistance increases. Also, shifting my gear makes a difference - when I shift to a heavier gear, I have more Watts output.

I also just found this setting in Tacx Utility and switched it off

To everyone who replied (thanks) and who might be following this: I ‘solved’ the issue by disconnecting the Garmin FR945 altogether from the Tacx Flux. Now just recording my HR with the Garmin, while Zwift is working with the Tacx to capture Watts. Annoying stuff, but this works at least.

Since Garmin provided a firmware update to the watch, in which it enables it to do structured workouts similar to Zwift, I might cancel my Zwift subscription. Only downside for the moment is that I’d have to manually put in workouts via Garmin Connect.

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Hi Vincent,

I am dealing with the same annoying issue. Forget about finding a solution at the Zwift or Tacx app settings. This issue is caused by the Garmin FR945 external sensor settings.

Garmin FR945 interferes the ZWIFT ERG controll. As you, I am also recording my workouts with the Garmin FR945 in addition to Zwift to get the Garmin FR945 metrics.

Sometimes the Garmin FR945 takes controll and prevents Zwift from changing resistance. Could be depending on which device (Zwift ipad or Garmin FR945) fist connects to the trainer. Do not know.

The only workaround I found, is to switch off the Garmin FR945 and turn it on only after I started the ZWIFT workout and checked that the resistance control works. A limiting factor to this workaround: if you need to make changes to the Zwift resistance settings during your workout (e.g. lowerering the target watts niveau of your planned workout), the Garmin FR945 again comes in your way and prevents this change. I needed to power off my FR945 several times lately, then waited for Zwift/ipad for taking over controll again. Very annoying, indeed.

UPDATE: issue could be cause because I added the TACX trainer as a TRAINER sensor type to my Garmin FR945. I will remove it and try to add the trainer as a Powermeter and Speed/Cadence sensor. This will do it.

When you pair your Flux to your Garmin are you pairing it as a trainer or power meter? If you pair it as controllable to Zwift and as a trainer on the Garmin you could run into issues like you mention. However, if it’s paired as a power meter on the Garmin there shouldn’t be a conflict.

I pair my Neo 2T to Zwift and my Garmin head unit and dual record and have never had an issue with resistance as it’s paired to Garmin as a power meter so Garmin can’t control it and send conflicting info, it only receives.

You could be right. I thought about that. My issues started when I paired the TACX as a trainer. I will try to pair it as a cadence sensor and power meter. Should work. Thanks!

Hi Bobo,

I stopped using Zwift in favor of a different product, but indeed the solution is to not connect the Tacx to your FR945 as a trainer. Cadance and speed works fine, yielding the results you want in both Zwift and Garmin.

Good luck,
Vincent