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Neo 2T – Phantom Watts

After even a momentary pedaling effort, Neo 2T continues to drive the flywheel at low watts after the rider has stopped pedaling. On a 0% gradient, the phantom watts drain slowly over approximately 30 seconds, dropping first to 0, then popping back to 4 – 5 watts momentarily, and then finally back to 0.

You may also notice that Neo continues to drive the flywheel forward at low speed for up to a minute after a has concluded, even after the watts have stopped at 0.

A demonstration of phantom watts in Zwift


RESOLVED Jan. 29, 2020 — Tacx have released firmware version .34 for Neo 2 and Neo 2T, within which is the solution for this particular problem. From Tacx:

Firmware .34 is online
* NEO 2 power linearity improved (this was also done with NEO2T)
* NEO 2T idle power fix (downhill corrections in power)
* NEO2 linearity fix: means on high speed and low power there was a big difference in wattage. (like when you ride in downhill mode)
* NEO2T idle power fix -> When going downhill you were still seeing some wattage when not pedaling (without cycling, like 8 watt)


This problem is a side effect resulting from the installation of firmware version .31

This problem was first reported by Krzysztof Tylek on October 13th, 2019. We confirmed and reported it to Tacx on October 14th, 2019. Tacx let us know a few hours later they are testing, but we have not had any additional communication with Tacx regarding this problem since the initial report.

Additional Information

All applications that use sim mode are affected, including Tacx Utility App Testing Dashboard. Erg mode applications like TrainerRoad are not affected.

Phantom watts only appear while the Neo is operated with mains power.

Concerns that phantom watts contribute to efforts while pedaling have thus far been disproven. We have not been able to demonstrate a scenario where a clear 7 – 8 watt disparity exists between a power meter (at a given offset) and Neo 2T.

Updated on January 29, 2020

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