After playing around with all the levels I have it set to “Level 1” as this gives me the closest match (which is not that close as you can see above). However, the slope setting in fortius goes from +20 to -20 in 0.2 increments and I don’t know how this relates to the 11 Levels in TR. I presume this relates to the slope settings in Fortius as I have to set the slope to +0.4 to be able to push enough power on the biggest gear.

The TR app shows the I-Magic for virtual power and within it it has settings from “Level -4 (Easiest)” to “Level +7 (Hardest)”. Am I even training at the right power for SS, VO2max, etc.? This is very annoying because I am not even sure what impact this has on training. So, as I increase power at a similar cadence, the deltas differ: -12W, 0W, +20, +30W. By the time I’m pushing 250W on TR, Fortius is showing 230W and my last sample point is 330W on TR, which results in 300W on Fortius. At 135W, both meters are around 5W from each other. Quoting rough figures, at low power, 108W on TR, Fortius shows 120W. This is far from what happens in my setup and I want to think this is due to the settings. So, if Fortius shows x% over TR at low power, that percentage to be similar at higher powers. I know some difference is expected, but I would expect (maybe wrongly) that the difference would be roughly constant.

It works well, except that the power displayed by Fortius and the power displayed by the TR app are different. This is a dumb trainer and is wired to a PC running Fortius software. According to the TR website and the TR app, my Tacx I-Magic trainer is supported.

Tacx fortius update