ERG mode wheel on Vs direct drive

So I upgraded from my tacx flow smart to a tacx flux s, I used it for the first time today with Jepson today in ERG mode as normal.

It was a very different experience and one that I did not enjoy. With the wheel on flow I never had to leave the big ring, I may have been a few watts over my recovery targets but no big deal, rest of time I was in the middle of the cassette.

But tonight I had to change to my lowest gear for every recovery interval, if I went back to big ring middle of cassette for the hard intervals I wasn’t constantly about 10% over target and was forced to change gear.
Also the intervals seemed much tougher than normal, I tired them in both big ring and small ring. When in the small ring the power reading were also a lot less smooth than the big ring. I’m pretty sure my cadence was consistent.

It just felt like the power was wrong compared to the flow and riding out doors. So I’m wondering am I missing something or has the much cheaper flow been wrong the whole time? Also I’ve never used my actual power meter on my indoor trainer.

I have the latest software installed.

Anyone any thoughts or is there really such a big difference between wheel on and direct drive?

I don’t think your differences sound typical for direct drive vs wheel on trainers. It sounds more like the new trainer isn’t functioning correctly.

Running in erg mode you shouldn’t have to shift at all with either trainer unless you are at the extreme far ends of power ranges (<50 watts)

As for the power discrepancy - it is hard to say - I’d definitely suggest throwing a power meter on the bike that’s on the trainer and at least comparing the data (or using power match) from the new trainer to that - will at least give you a trusted reference point to see if it is accurate

Yeah I plan to throw the good bike on both over the weekend and see how they compare. Bit of hassle as I have an old bike permanently set up in the attic that won’t take the power meter!

My initial thoughts were that it’s not working correctly but hoping someone might have a suggestion

So I used the power meter on both trainers today for a bit. I found the flow to be quite a bit lower than the power meter. However the flux was much closer to the power meter, power meter las left side only so not worried about a small variation.

What I did notice is that when using the flow, I was using a garmin speed/cadence sensor because the flow was never accurate. With the flux I was using the flux cadence value, in an interval I found that the flux was giving a cadence of 130-150 while my actual cadence from the power meter was 90-95.

Would this possibly be causing some issues of how the trainer handles power control if it thinks I’m spinning at crazy cadences?

Cadence cod be an issue, but only if it is fluctuating a bunch. Fast or slow doesn’t matter as long as its “smooth” and comsistent.

If its bouncing around, it will lead to ERG issues.

I did palisade today and synced to my garmin cadence sensor, the first 2 interval blocks nearly killed me, really struggled. I then changed to resistance mode and it felt much better, tough but manageable and more what I expected.

I’ll do another work out and get my power meter set up properly on it for a good camparison and see how it goes. :frowning:

Any updates on this? Really interested to hear as Flux S is the trainer I consider purcahsing but if it has constant problems with ERG then may just need to spend some more.

Yeah I did two complete workouts, Spencer and Darwin

Spencer was the first attempt, I was changing between small/ big ring ERG for first two intervals, then small/big ring resistance for second 2 and then power match for the last one. The first 4 intervals the flux did rear a bit lower than my stages

Did the same for Darwin without the power match bit and it tracked pretty much bang on.

The timing is a bit off as I pausing TR to change between modes so you can ignore that.

I think my flow just wasn’t as accurate so i’m getting more realistic reading now.

But I do find my self using resistance mode now more than ERG depending on the workout, I just find the gearing to me more realistic for me that way.

I think the Flux 2 that being released soon has done away with the belt and has a much improved resistance floor

I should also point out that I have not done a ramp test on this trainer yet, so I expect my FTP to drop as this seems to give a lower reading than the flow, so my initial problem of really struggling to complete workouts in ERG may be resolved when I do a new ramp test


I bought the FLUX S about 4 weeks ago. Before I used a TACX Vortex Smart. I am using a Power2-max Powermeter in combination with an ant±Dongle.

For me the ERG-Mode works fine, when I am using the smaller ring in front (34) and in the rear a gear something between 30 and 25…

BUT I have in big issue with the device, when I am doing a SST-Training with higher wattage and right after this a cool-down part with about 85 watt is coming. The software or the trainer cannot address the 85 watt. I am on about 110-120 watt. If I doggle between ERG-RESISTANCE-EG-Mode manually, everything is fine again. After this switch the trainer can hold the 85 watt without any issue.

I do not know, why I often have to doggle between the modes. When I am doing a endurance-training with about 140-170 watt, the software/trainer addresses the wattage perfectly.

I think it is not related to the wattage-floor, because, the trainer can do the 85 watt, without a problem (if I switch between the two modes).

Yesterday I did a test with Zwift, and I did not have a problem.

So it is hard to say, if it is a problem of trainerroad, the trainer or a combination of that.

best regards


You both @Shoco and @Martin_Peinsipp have powermeters, but would you notice that Flux S is not at 85 W but say 110 W between intervals if you were not using a powermeter? I mean you might feel it but what does it say on TR screen target vs current power if using only Flux without powermeter? I’m asking as I don’t have pm and at the moment don’t have the Flux either.
Is that toggling between ERG-RESIST-ERG something you can do on the fly during the TR workout?

My flux struggles to get below 100-120w without changing gear, it’s a bit of a pain but the reaction times and consistency at higher wattages is worth it

Just change gear then :relaxed:

My flow is the same, it was also the same for big stomps. A change here or there is not the end of the world.

If in ERG mode I would have to be in my lowest gear 34/25 for it to hold 85 watts, any bigger gears it seems to struggle. I may even have to reduce my cadence to meet those targets sometimes, resistance mode seem to work much better if you know the right gear to be in and have the resistance set correct

To change between ERG and resistance you have to pause it and go into the settings, though @Nate_Pearson did say they were hoping to add a button to the workout page to make it easier.