ERG mode and Tacx Vortex

I was wondering if anyone else has the same problem as me: In ERG mode on my Tacx Vortex Smart there seems to be a power “ceiling”.

In the hard (over 400watts) intervals the resistance is way too low to generate the necessary power.

I’ve had a little help from Zwift, suggesting interference on the ANT+ connection. I switched to BLE and the problem remains.

The same thing happens with Trainer Road and Tacx’s own training software.

I’ve also contacted TR and TACX but no-one seems to have an answer. 

Has anyone else experienced this and if so do you have an answer?!

Have had similar problems - are you using the Tacx Vortex for cadence? I’ve found it’s much easier to generate the higher power outputs in ERG mode if I use my Garmin speed/cadence sensor

Hi, no I use a separate speed /cadence sensor like yourself 

I tried the workout mode last night and was having trouble hitting the 435 watts power output in the hard intervals. I had to shift all the way down to my hardest gear in order to get close to 430 watts. The resistance wasn’t high enough for me to go past 435.

Am I doing something wrong?


You’re not doing anything wrong  - I’m having exactly the same issues but Zwift support do not have any answers. I’m having identical issues with trainer road so suspect there is a problem with the Vortex which is a real bummer because they aren’t cheap and Zwift recommend them.

The only way for me to get a workout in erg mode is to use the gears aggressively but apparently you’re supposed to find an easy gear and let the trainer apply the resistance - just doesn’t work!

I am having the same issue. Having to change gear to hit the wattage and cadence in workout mode. I have bontrager speed cadence sensor so will use that instead of the vortex on the next workout to see if that sorts it.

Just looked at the speed cadence data for my last workout and its all over the place compared to the Power and heart rate which are relatively constant.

I have just moved over to a smart trainer. I used to train regularly with heart rate and cadence on a dumb trainer so I know how to hold cadence, so not driver error!


What is the advantage to use ERG mode for workouts. I don’t have ERG mode on my trainer so I don’t know what I am missing. Isn’t it just easier to turn ERG off and change gears and resistance manually?





might have found the problem… 

Last night I used to begin my “sprint” a bit before the hard interval so my cadence was way higher than usual. Because of that, the trainer assumes you can keep up the high wattage at that cadence, making it way harder to hit the target wattage.

I just did another workout 20 minutes ago and tried keeping my normal cadence of around 85-90 when entering the hard interval. Automatically, the trainer ajusted the resistance to my regular cadence so I was able to hit 350 watts at around 100 RPM.

Will test a bit more in the coming days just to be sure that it really works. But it was way better today!

Hope this helps.

Tonight instead of using the Vortex for speed cadence I used bontrager speed sensor and have had better results. Consistent cadence and speed. Not telling me to speed up/ slow down all the time. Also able to hit wattage using the same gear.

Any resolution here? Having the same issue, or similar at least, but just now. As soon as I hit any slope, my max wattage is 75. That’s literally it. I can hammer until I smell smoking rubber, no difference. The wattage ceiling is ridiculously low, but I didn’t have this issue last winter. I’m pretty sure it’s a trainer issue as the wattage has been ridiculously low when I try out the Tacx workouts too. 

If I disable ERG I can at least get some sort of workout in but it’s kinda a waste of the smart trainer.

I’m  having similar issues with tacx vortex smart linked to a brand new MAC…

Is there a solution?

Is this a Zwift issue or Tacx?

Nearly a year on from my original post and I can offer these observations: It’s still almost impossible to hit short bursts of “sprint” type intervals at high wattages, but with carefully timed gear changes, workouts at around threshold are achievable - i.e.intervals between 200 and 400 watts.  

I think one problem for the shorter intervals is the lag between the start of the interval and the trainer adjusting its resistance.


Did some1 try to solved this problem with Tacx?

Yes - I discussed the problem with Zwift and Tacx. Zwift rely on the power output from the trainer so they could not help. Tacx dodge the issue…

So you dont use ERG mode in Zwift on Tacx Vortex?

The things I´ve found out with this roller so far are…: TACX VORTEX SMART:

It is not that accurate… power readings vary from up to 10%… actually from my crank power meter (sram Quark) … and the cadence… I don´t know!!! some days exact some days not… I prefer to use the bike cadence sensor mounted on the crank.

Pairing to Zwift it is very easy!! I use an iPad 6 new generation… with BLE only by bluetooth pairing… and works fine.

The Vortex eats literally the rear tire…!!! in just 2 months my pirelli potenza finished like F1 car tire…and have to throw it away… I have not tried the specific roller taCX sells … but will.  Smokes everywhere…and the kids and wife noticed that… prepare to do the riding out at the garden or somewhere else or the house will smell like hell !!! and obviously you should check the pressure and calibrate with the Tacx utility app every ride. And the tire will not wear evenlly, I have to use a rope to constantly clean and remove debris so I can ride “smoothly” during the session.

Training:    Specific Workouts you build… work fine… but here are the tricks so far I use:  when you are riding for example at 220 W cad 95… and you need to jump or about to reach an interval or hitting higher wattage… you have to slow down you cadence 5 secs before hitting the wall… like 80 or 85 depending on the targeted wattage… like 300 so the Vortex can adjust the brake (obviously ERG mode ON)… automatically…then rise your cadence again to 95 or 100 in order to maintain the watts and works excellent… I tried the NEO taCX roller and the same thing and also a Wahoo … same trick… for all !!!..

Zwift riding:   When hanging around the Watopia roads… or doing a race or group ride… same tricks work…

Sprints: while racing…on the Vortex the thing is when you are going to do a sprint… cadence will blow your legs and the watts not (sadly)… its very hard and disappointing to get past by another rider that could push really hard and the wattage increased accordingly to the effort… and you just not !! once in a race I was frustated because on the final sprint the max I could reach was (over a cadence of 177 rpm !!!)  583 watts max, had to put all my smallest ring on the cassette… my legs exploded… and lost, the Vortex did not applied the resistance on time and the cadence flew… I need to find out what to do in those sprints…

In some intervals training, if they are built whit a really short amount of time and huge changes… it is better to do them with  the ERG mode OFF… but not recommended above 300 Watts or they are going to be very hard to do them or the Vortex won’t have the time to adjust… specifically if they are done in less than a minute … although I think it is just a matter of cadence or pace… like for example if you are riding at 175W 95 rpm … and suddenly there is an interval at 280W the Vortex just brakes like crazy and becomes too hard to keep it at 95 rpm or more because you have in deed have to push more and rise the cadence… so in reality feels like 450W !! but in zwift just 280W and saying “rise the power”… and your legs blow, the cadence falls and frustration grows jajaja… but if you do the trick stated before… you eliminate this… but it works better for longer intervals… because if you don’t maintain the wattage targeted the ERG goes OFF.


The finale resume:    you get what you paid for… the Vortex and Zwift is really good but not perfect… buy the taCX Neo smart and solve all the issues, and also not perfect but much better… one relies on the tire and the other on the cassette… resistance changes better but for rides around 0-300 Watts with a good tire will make the fun out of it.


Doc Gerry (México)