Taxc Vortex seems to be off the power scale

Hi all,

for me it looks like my Vortex is absolutely over the power scale. Yesterday I did a FTP ramp test in ERG mode. I started with 100W and ended up at about 420W resulting in a 305W FTP which looks like far too much for me as I am not a really fit cyclist and didn’t do much during the winter. I looked a little bit strange right from the beginning: The test starts with 100W: I was not able to reach the 100 because the trainers ERG mode measured 120W all the time. I did not feel any resistance at all and it feeled like freewheeling. At 140W I started to feel some easy resistance. Going up to 260W it was quite easy pedalling. From 300W onwards it started to get a litte bit exhausting and at 400W I started to struggle.
For me it looks like the measured power values are about 100W too high. What am I doing wrong? I added some pressure to the backwheel and recalibrated the trainer in Zwift and with the Tacx utility.

My setup:
Tacx Vortex (Selected for power and as adjustable trainer) conncted via ANT+
Cadence/Speed Sensor (Selected for cadence) ANT+
HR Strap (obvioulsy) ANT+
Windows PC

1,95m tall

The FTP in older tests was also between 280W and 320W. So it looks like stable values, depending on my training. I started wondering about the values because friends of mine who are a lot fitte than me got FTP values between 210 and 250W with their direct drive trainers.

I would be very thankful for any suggestions fixing my setup

Kind regards

Hi Eric,

thank you for the suggestions. Actually:

  • The Tacx Utility tells me the latest FW is installed
  • I use a Schwalbe training tyre because without the wheel was slipping a lot
  • The calibration is in the righter yellow/orange area. As you said in the green area it slips too much
  • I did a calibration before and after the FTP test but nothing changed.

For me it looks like the main issue is the 100W freewheeling. 100W should add a noticeable resistance or am I wrong?