Tacx Trainer power calibration variation - how much down to tyre, how much trainer? PLUS does a trainer tyre get impacted less by temperature?

Equipment
1

Anyone got any info on this? Wondering how much of the power variation on a wheel on trainer is down to the trainer warming up and how much is down to the tyre?

A secondary question is has anyone found a trainer tyre to be any more stable / seen less power variation hot to cold?

For reference I use a Schwalbe Pro One @ 100 psi on a Tacx Genius. I have rarely seen much difference in calibration tightness between cold and after 10 mins use when Tacx suggest you should calibrate.

Why I ask today? Here it is 7 degrees / 45f and I for the first time ever it asked me to add tension after a 10 min warm up. I was also using a second power source for the first time, it showed some drift between sources both from cold to 10 mins when I calibrated but then again from 10 mins up to about 15. This was 20 watts at cold, 15 watts after warm calibration then about 20 watts after a further 5 mins - all probably within the tolerances you should expect from a wheel on trainer but something Iā€™d be interested in avoiding if possible.

2

To close this out in case anyone comes back in the future.

I managed to get a very close correlation (versus a P2M crankset meter) by running 110psi and calibrating after a 30 min ride. That tension is slightly out when stone cold but quickly comes up to align with the P2M and even giving a very similar number.

So my top tip - calibrate the trainer at the end of a decent length session then use as similar a psi as you can from then on. If you calibrate when cold prior to a session you will see the variance unless you do so again once warmed up. If the ambient temp changes hugely then might be worth another warm calibration.

1 Like