Hello! Wondering if anyone knows if the TACX vortex (2180) reports power consistently (-faulty) along the power curve, ie if it is always off by the same amount?
Workouts in Erg feel ’about’ right, vo2 is very hard, endurance easy etc. so even if absolute numbers are off by say 10-20 watts, I am happy if the errors stay the same.
IF, however, the resistance it spits out for say 250 watts can sometimes be equivalent to 240 and sometimes 260, then I am bummed, sort of would make testing, measuring progress pointless.
Experiences in how errors vary by gearing, if trainer is hot/cold, tire psi etc would be very welcome!
Love the forum and the amount of suffering TR brings!
I think the power curve is fairly consistent, but not necessarily linear. That is, at eg 100W, it might be too low, and at 300W, it might be too high. That is why TR have developed powermatch, which makes the trainer do the power actually measured at a powermeter (if you have one).
The big thing with wheel-on trainers is that the power depends on the pressure of the rear tyre, and tension to the trainer. The tyre pressire obviously depends on temperature, but if you keep the trainer indoors, the variation shouldn’t be that much, imo. If you keep the tyre pumped up to the recommended pressure, and calibrate the trainer before the ride, it should be pretty consistent.
From my experience of using 3 of them, they’re pretty much random number generators! The best advice I can give is to set the resistance on the tyre so that (when the tyre is warm) the calibration is right on the ‘too tight’ edge of the scale. That’ll get it close enough at say 200 watts, however the curve isn’t right so at 300 you might only be actually doing 290 and at 400 it could be as low as 360. It’s a great trainer but best used with a power meter.
I’m using the same trainer with no problems. It just needs a bit more calibrating before every workout. I have my Tyre pressure at 100-110 psi, the calibration with the tacx soft and just near the TOO TIGHT bar, and always recalibrate in the TrainerRoad app.
All the calibration should be done after a couple of minutes of light spinning ( to get some heat in the tyre ).
Mine was pretty consistent in terms of the numbers it out out. However, the issue is the slope of the power profile. At threshold the power numbers match my assiomas very well (a few percent out at most). However, at high and low powers there is much more variation. At VO2 max the trainer can read 20-30 W low, and in recovery 20-30 W high.
I found this out very quickly when I got my power meter as VO2 max workouts suddenly became doable!
This was all based on a spindown calibration when warm and consistent tyre pressure set with a digital pressure gauge.
That is well within Tacx’s advertised margin of error which is about 10% on the vortex. From what I hear from tests done with power taps is that vortex reads too low at low wattage and to high at high wattage. The response time is also long abour 3 sec lag.
Thanks for all the useful insight! Might just have to bite the bullet and start a ’protocol’ before key rides, checking psi, calibration etc. Bit confused though if there is a general ’rule’ to how power is reported along the curve even after calibration efforts
At VO2 max the trainer can read 20-30 W low, and in recovery 20-30 W high
This would indicate it generally gravitates towards the middle? Underreports at high power etc?
vortex reads too low at low wattage and to high at high wattage
at 300 you might only be actually doing 290 and at 400 it could be as low as 360
Whereas this would mean it ’stretches out’ the numbers, inflates at high power etc?
Sorry if I am getting it wrong. Maybe it varies between each trainer
As long as you’re not trying to ride at exactly FTP and are staying within 200-300w range it’s not terrible, so in their defense for most customers it’s a decent trainer.
Also note that those numbers (which are off the top of my head, but about right) are based on the roller being right on the ‘too tight’ end of the calibration - if it’s in the middle you can add maybe 30 watts to all the reported numbers.
At the time they were the best ~£500 turbo that was available, so I bought one, then another to replace my partner’s, then recommended a friend buy one with the caveat that I’d need to come and calibrate it for him. So I’ve long term experience with a couple of them and have done the same calibration test multiple times - we used to do it every time we changed tyre in order to set the roller tension properly.
