Connecting to wrong turbo trainer

My wife and I both Zwift at the same time. When starting Zwift on either laptop it often connects the controllable to the wrong turbo trainer but the power is always for the correct one. We have 2 trainers and 2 laptops, we do not ride using each other’s setup.

My wife uses a windows laptop and a Tacx Flux 2
I use a Macbook Pro laptop and a Tacx Flux 2
Both machines have bluetooth switched off and have ant+ dongles attached.

When I set up Zwift on the machines I do it with only one of the trainers and one of the laptops switched on at a time. Looking in knowndevices.xml after this there is only 1 trainer mentioned (repeated 3 times for power, cadence and controllable). After one ride I’ve noticed that the other trainer is added at the bottom of the knowndevices.xml file, even though I have not pressed the search button. Then in subsequent rides it appears to randomly pick which trainer to control, but always picks the original trainer to read power from.

I have tried deleting knowndevices.xml as well as a full reinstall of Zwift to no avail. I have tried this on both laptops.

Below is the contents of knowndevices.xml after installation and setup

[0] [729369] [5835684] TACX PWR 8473
[0] [1122585] [5835684] TACX FE-C 8473
[0] [7938329] [2139619358] Speed/Cadence 8473

Below is the contents after the first ride with both turbo trainers switched on

[0] [729369] [5835684] TACX PWR 8473
[0] [1122585] [5835684] TACX FE-C 8473
[0] [7938329] [2139619358] Speed/Cadence 8473
[0] [1121757] [5835684] TACX FE-C 7645
[0] [7937501] [0] Speed/Cadence 7645
[0] [728541] [5835684] TACX PWR 7645


On my trainer I always connect to the Elite FE-C settings.
The other settings don’t work correctly on zwift.
I suggest that you try just connect to the FE-C for power and trainer.

If that doesn’t work, come back and ask again.

I’d probably use ANT+ for the Windows machine and change to native Bluetooth for the Mac. And as Vlad says, always use FE-C.

I can’t see how having one laptop using bluetooth and one using ant+ would stop the issue as I can’t disable ant+ or bluetooth on the trainer as far as I can see, so Zwift would still jump between them, I’ll test this over the weekend. I just don’t see why Zwift doesn’t either honour the LASTCONTROLLABLETRAINER setting in prefs.xml or at least ask if I want to change trainer rather than just selecting the first trainer it finds.

On the FE-C option learn something new everyday so will update that.

Bluetooth removes itself from being visible to other devices once paired, whereas ANT+ just broadcasts openly to all and everything all the time. That’s why I think mixing the two may be a solution to your problem.

But if the windows machine is still using ant+ it will still be able to connect to the wrong trainer, which means we’d still have to watch the device selection screen closely to ensure it picks up the correct trainer. Not sure if this bug will affect a bluetooth only laptop picking up the wrong device either will have to watch that.
NB this is not happening during a ride but on starting Zwift.

True, but the Mac would only be able to see Bluetooth so at least that one would be sorted and you’d only need to check the Windows machine had picked up the right trainer which would be trivial at the pairing screen upon login. Power, cadence and controllable should all be TACX FE-C 8473 (or 7645, whichever is the ANT+ trainer).

But the mac would still see both trainers on bluetooth and the windows machine would still see both trainers on ant+ when starting Zwift. Unless zwift treats connecting to devices differently via bluetooth than via ant+ I don’t see this as fixing the fundamental bug that zwift changes which controllable it connects to without user interaction.

As a side not I do have dedicated cadence devices but excluded them for simplicity as it never changes which of those it connects to. Zwift also never changes the power connection it is just the controllable that changes. I have also noticed that it takes longer to pick up the controllable vs the power connection when arriving on the device page.

Probably need to do it in order;

  1. Mac on, BT trainer on and pair (removes BT trainer from visibility).
  2. Windows on, ANT+ trainer on and check correct device is picked up.

I’ll try that and report back after a few sessions over the weekend.

Sorry life got in the way of testing. Problem with using BT was that my cadence sensor on the bike is ANT+ only. So still have the issue with the wrong controllable trainer being picked up. I’ve also noticed on my last session that it picked up my wife’s cadence sensor instead of mine, first time I’ve noticed that.

Your trainers transmit cadence, you don’t even need separate sensors for that.

The other thing I didn’t realise was possible on the Flux 2 is that as per the Neo 2/2T/SE you can disable boggo ANT+ speed/cadence broadcasting (leaving FE-C turned on). That will clean up your wireless environment even further; I’d do it on both.

But I’ve found the trainer’s cadence report often lags behind my legs and sometimes is just wrong. I’m guessing as it is because the trainer infers cadence rather than directly measuring it.

Didn’t know that they’d added that to the Flux 2 thought it was only Neo. I’ll have another look

That’s odd, I never had that problem when I had a Flux, though mine weren’t the 2. Is the firmware up to date? Worth checking if you’re getting the Utility app up to check the broadcasting toggle. Be careful if you’re out of warranty though…

I’ve just disabled boggo ANT+ speed/cadence broadcasting, definitely makes the list of devices easier to check.
Just checked firmware is up to date on both trainers.

I’ll have to live with Zwift changing its mind on which device it feels like connecting to today and be careful when starting.

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If there’s only FE-C being broadcast then you may find the connecting to the wrong trainer thing isn’t as bad. A cheap Bluetooth-capable cadence sensor for the trainer using the Mac would allow you to keep them on completely different protocols and may be less frustrating, albeit at cost.

At the moment I’ll stick with it as is. In a few months I should be getting a new road bike and can leave the current bike solely on the trainer and will look at going down the bluetooth only route.

Thanks very much for your help.

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