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: