Tacx Flux doesn't play nice with ERG mode

Does anyone else own a tacx flux and struggle with ERG mode especially? If I use ERG mode I find that my power refuses to stay at the desired power target, either being well below or well above. When ERG mode is off I find that my power is all over the place and I can’t maintain within even a 30 watt range… Does anyone have recommendations on a smart trainer that is compatible with TR that they don’t often struggle with? Let me know!! Im desperate.

Been using a Kickr since 2017. Been solid for me. Never had a drop out. Works in erg, resistance modes. And Power is spot on with my Quarq Pm. Highly recommend

You will find some people had problems a few years back with quality control. Wahoo changed manufacturers and had issues. But they’ve resolved that now. And customer service is great if you ever need help.

i do have a tacx flux, it works perfect for me but u have to consider some things.

1.) do not use ur Powermeter as a source and the trainer as a resistance ( i used to do that on zwift, doesnt work at all) im not even sure if TR supports that.

2.) u still have to be in a somewhat right gear for ERG to work correctly. If you are doing 300 watt intervalls on the small ring and a big sprocket, it wont work well, same goes for big ring and Z1… u still need to shift a bit manually. i would recommend try out some different gears for a set wattage and look how the graphs behave.

Conclusion: if ur trainer is not broken, it must work eventually


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The Tacx Flux is a usually a good trainer and is fully compatible with trainerroad (and powermatch if you have a PM).

I would reach out to TR support support@trainerroad.com to see if they can help.

In your situation the first thing I would do is look at your connections as it could be you are getting lots of dropouts or interference?

Experiment with swapping between ant and bluetooth and try a USB extention for your dongle if possible. Also make sure that no other devices are connected to the trainer by accident.

Of course it could just be that you have a faulty trainer?

In summary the Flux should work just fine.

This sounds like the same issue i had with my 2021 Flux. I spent 10 frustrating days trying to get it to work in erg mode and finally gave up on it. I returned it and bought a Kickr Core which worked perfectly right out of the box. Good luck with yours and hopefully you can find a solution.

Are you coming from a Kickr? I ask because if so, this is a frequent complaint because people are used to the way Wahoo artificially smooths the “line” to make it look like your power isn’t fluctuating. Humans don’t hold exact wattages, they fluctuate with every stroke, and the Tacx products expose this.

Definitely shoot TrainerRoad Support an email.

I’d also try a few different things to establish if it’s the trainer and not some other piece of equipment. For example I was having issues with Erg mode (Kickr) but only when running TR off Android with Ant+. Android BLE, Windows and Mac all seemed to work fine. So first off I’d try swapping connection from BLE to Ant+ (or vice versa) on the same device, and then swap devices (if you have another available).

I have that issue once in a while with my Tacx Flux S, it gets stuck somewhere in its little brain. Did you try cycling the power to the trainer? That resets the controller; power management in Tacx trainers appears to be pretty dumb, the controller seems to stay powered up even if you let the trainer unused for hours or days. Once that poor little brain is off the rails, it will stay that way until you reset it.

That’s what it looks like when that happens.

How steady is your cadence in those cases? I assume you are using the trainer as the source for power measurement? Can you show an example of the fluctuations you observe? Both in erg and resistance modes?

I use Powermatch on a Tacx Flux S with Assioma pedals - which is exactly what you say not to do - and it works fine. TR supports it, it’s what Powermatch does.

i had a tacx flux for 2-3 years but never ran into those problems, sorry!

have you made sure the firmware is up to date on your trainer? that’s the only thing i can really think of that’d help out!

I’m betting it’s the Wahoo effect

@Karlie_Childers The below notes would be important to know. Of course the standard troubleshooting of calibrating and all of that is important, but beyond that, there are a bunch of factors.

  • Which Flux model do you have?
  • What wattages are you trying to hold?
  • What cadence are you riding in?
  • What gearing are you in on your bike?
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That and some links or pictures of the related rides for review could be useful.

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Potentially, also - are you connected to any other software/devices intentionally or not, this can throw the ERG control.

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3 rd year of ownership of a flux s and my third unit after the first two units being replaced, the last unit was outside warranty but Tacx sorted me out.

Do you calibrate before each ride?

The flux is slow to work up to the required watts. Make a mental note of what the target watts are and then run the trainer 4% over target and you’ll find the power settles around where you need it to be to be compliant. Yes it’s a faff but it works and saves you chasing 3-5 watts. As for Vo2 intervals, good luck as they are challenging to hit the right power but the warms up help gauge where you need to be in terms of power and cadence. Just up the cadence and power 1-2 seconds before the interval starts

Keep your cadence consistent and you’ll need to use a third party cadence sensor as the flux option is simply rubbish.

Is your firmware up to date?

If your still in warranty just exchange the unit or see if you can get a Neo at a discounted price. You’ll have to go direct for that outcome though as shops don’t have access to that deal.

Bottom line they work but not as well or as smoothly as some of the competition. There’s a Facebook user group which is a great source of information, if like me you’re out of warranty and need to keep the thing running.

The neo 2 is on offer currently (UK) and I’m considering an upgrade but there are some smart rollers from Wahoo which have just been released. Rollers provide a good core work out too so I’ll probably defer for a couple of months and see what new users report.

So, Ive actually teied almost every suggestion listed in the comments above. I hold an 85-95 cadence. I have a tacx flux 2. I’ve got a pretty standard 12 speed. If It’s a steady recovery ride of 130-140 watts its usually okay. If I’m doing VO2 max or anerobic work outs my power will not reach the intended target. Either the power stays the same without an increase in resistance or it holds it for a brief moment nearly 20+ watts below the target. Its not a personal strength issue here, I can do these workouts off the trainer just fine. My boyfriend also has a trainer so I used his trainer one day and had no issues. I have an ant+ dongle cable which I use and I typically shut off the bluetooth connection, I calibrate before every ride… I swear this trainer is just THE WORST.

Sorry if im not the brightest, but “cycling the power” means? I have a new flux and it doesn’t drop to low watts in the recovery troughs.

“Cycle the power” = pull the power cord out of the wall, wait a couple of seconds, plug it back in.

Your issue may be caused by the “floor” below which the Flux won’t go résistance-wise. Try shifting to your easiest gear in the recoveries, and see if that fixes it.