Going from wheel off to wheel on trainer

I have a Tacx Flux S and this is the first time Im hearing of them being wildly inaccurate… I find it hard to believe theyd be less accurate than a wheel on trainer…


Very interesting! Thanks for sharing.
Link to Screenshot: https://www.dcrainmaker.com/2018/07/first-look-tacx-announces-new-flux-2-smart-trainer.html

For fun, see attached screenshot for how badly the Flux 2 handles in ERG mode. This is compared to two the PowerTap P2 and Stages LR. There’s two core issues:

A) It can’t hold ERG mode properly at a given level without large swings (for which Tacx has confirmed)
B) It’s simply inaccurate by 10-20% (for which Tacx has also confirmed)

I started calling this out back in March on my post in the comments section, waiting for fixes. I had other warnings as well on it before finally giving up and just sticking a big old ‘Do not buy’ in bold at the top. It’s just not good.

The Flux 2 was also quietly updated at Eurobike, dubbed the Tacx Flux 2.1, to address these. More on that soonish.


Also note, this is specific to ERG mode, not SIM mode. And it doesn’t matter if it’s ERG mode on TR or Zwift, I tested both and both suck with the Flux 2.

However, SIM mode, such as regular Zwift riding, is just fine. See attached for that (the spike you see is me doing a mid-ride calibration



You can read through the thread I posted a couple of months ago when I was trying to decide between a used Snap or a new Core. I have a power meter, so I use powermatch. I’ve never really had issues with tires wearing out with my old PowerBeamPro, but I also split my training between indoors and outdoors. I ended up with the used Snap, although I haven’t done much on it since it’s still nice here and I’m still doing intervals outdoors. I think you’ll really like having the power meter on the bike because it means you’ll get power outdoors as well as indoors.

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You could also go super cheap and get a Kurt kinetic wheel on dumb trainer and Assioma pedals. This is my current setup and completely hassle free.


My Flux S displays this exact behavior, is it just the 2 you tested?

If erg mode is the concern… then why not get the h2 or h3 as Ray also mentioned how great they are for erg?

I have the same. The idea of a direct drive is fancy…but I really wonder if I will appreciate the $800+ in extra cost.

If you’re not obsessed with a direct drive trainer there’s one system that could really change your value equation. You can pick up the inside ride ultimate Flex and connect your power pedals as the source. Then you have decent smart resistance with full rocking control, all floating on a motion platform. And they can be converted to smart rollers just in case you get the itch to ride free. I love mine… they rock!

I tested both. Zero issues with Flux S in that regard. Pretty different internals actually.

Bit out of my price range - plus I don’t think they are available in the U.K.

But if you take the money you save and get a power meter that you can now also use for outdoor riding, and let that also control your wheel on smart trainer’s erg mode, you are coming out well ahead.


That’s exactly my thinking.

I’ve ordered an M2 which works out at £280 and a set of Vector 3’s for £400 with %10 cashback to come. So about breakeven in the end.

On paper yes but then you might as well have a fluid trainer and the power meters… it’s relatively easy to hold constant power in that scenario.

The 4th popped tube in as many weeks put an end to my usage of wheel on trainers though I use a power meter as my source of truth for the turbo anyway.

That’s wild, it’s doing almost exactly the same thing.

Wow. I’ve been using a fluid trainer for 2 years and have never even changed the tube??

I do have a trainer tire on it though. I’d be done with wheel on after that if I were you.

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Something is very wrong with your wheel/tire if you’re getting a flat a week on the trainer. Rim/tape damage?

For someone with budget to be thinking about a wheel-off trainer, I’d still vote for a smart trainer over dumb trainer, even with power on the bike, because without that you won’t have ERG mode. But if your total budget was say only $500, then I totally agree that makes sense.

put another way, my take -

$500 to spend - dumb trainer + power meter
$800-900 to spend - wheel on smart trainer + power meter
$1300+ to spend - wheel off smart trainer + power meter

If you live in a place that you never ever imagine doing a structured ride on the road, and have no ability or interest to ride anywhere outside that using a power meter might be relevant, such as pacing climbs, triathlons, fondos, etc. perhaps then it makes sense to exclude that requirement.

But there are so many threads of people wondering about their indoor/outdoor offsets and meter/calibration differences that I don’t see the point to go down the path of fancy indoor trainer to get 1% more accuracy and then have no outdoor power just because you’re worried about tire wear. Most of us have an old beater / stock wheel and extra nicked up tires that are no longer roadworthy if it’s that big a concern.


Agree with that. Just to add on this, I use “dumb” wheel on trainer from Elite and experience almost no tire wear so I can use my regular wheelset with Conti GP / Schwalbe Pro One tires without problem. This could be because of Elite’s elastogel.

Indoor punctures are weird but I have experienced them also. My explanation is, there are probably some small sharp object in the tire from riding outside that make their way though the tire only on the trainer.
Once I have converted to tubeless, the problem vanished.