Tacx Vortex Power vs Powermeter Power while riding ZwiftI

I’ve been riding Zwift for a couple weeks now and still trying to figure out things in the virtual world.  Please help me out.

First, I calibrate both my Tacx Vortex and my powermeter.  However, when I ride, the Vortex is usually way off.  For example, today it was reading 280 watts compared to about 220 watts from my powermeter.  I like using the Vortex in Erg mode but feel like I’m cheating myself by not riding at the appropriate wattage during workouts.  I’ve never had an issue with my powermeter before so feel that is probably more accurate.  Only had the vortex for about two weeks. 

I don’t mind the tacx vortex for just riding along power but during workouts it does not seem accurate. 

What are you all doing when you have both a smart trainer and powermeter?


I’ve also done a couple of dual rides with the Vortex and whilst my power meter and Tacx do give different readings I’ve found it to be about 15-20 watts the other way round with my turbo reading slightly lower. I presume it’s just a set up thing? but I’m no expert.

I have found that if my tyre is under inflated I get an extra 30-40 watts of power on the trainer. It’s generally recommended to be 100-120 PSI. Zwiftblog has a nice guide on using the Vortex which covers issues and a set-up guide.

I’ve ended up just sticking with the Vortex as my power meter is on my ‘outdoor’ bike. The main thing is that when set up correctly my vortex results seem consistent day to day so hoping any power gains over time are real!




I also have a power meter and a Tacx Smart. When comparing them, I found the Tacx to be way over the power meter when cold during the warmup. Later it was under for a while and sometimes spot on. For the whole workout of 2 hours the difference was only 1 watt.

With this experience, I don’t use ERG at all in my workouts. I then use my gears and the possibility to change the restistance in the app to get the watts I aiming for. I always use the power readings from my power meter but I let Zwift change the resistance when I do free rides and races.

Therefore I don’t care about the calibration of the Tacx anymore, since the watts from my power meter is the only thing that matters. :slight_smile: