CycleOps H2 over estimating power when using high gears

Hi everyone,

Last fall I started using TR to prepare my first season as cyclist (used to do triathlon until last year), and I am loving it! However, I also love to race! So I decided to do some Zwift races to keep the motivation high.

On TR I use the Assioma Duo and Powermatch with CycleOps H2. From the various review sites, I saw that none of them have accuracy issues (with all firmware up to date).

On Zwift, I decided to use the trainer, just because I thought that is what most people do, and I expected the Assioma to read slightly higher (since they measure power at the pedals, with no drivetrain loss).

Then, after watching a video from Lionel Sanders, I learnt about the Zwift Powe analysis tool… and I decided to compare the power from the Assioma Duo with the power from the H2…

Contrary to my expectations, the Assioma Duo were constantly reading lower on the Zwift races I analyzed. And lower by 5%, which is a lot.

I did a bit of experiments, and I came to the conclusion that the gear that I am using (or the speed of the flywheel I guess), are impacting the H2 power measures.

For example, I did Truuli tonight, and I saw that if I use a 36x23 the power of the Assioma Duo and the H2 are very similar. However, if I switch to a bigger gear like 52x16 (what I mostly use on Zwift), there is a discrepancy.

See graph below:

Interval with 36x23

Interval with 52x16

Interval with 36x23

Interval with 52x16

Cool down
Interval with 36x23 first half, then 52x16

No big deal in real life racing, but I just hate to be unfair and I am now racing with the Assioma Duo on Zwift.

Did anyone see something similar?

Is there a solution?

More info:
I did notice this on Zwift races when doing a “hot calibration” of the trainer with the Saris App, but the graph in this message are registered after a cold calibration using TR. Assioma Duo always calibrated before the ride. So I think it is not a calibration issue.


Found some answers here:

1 Like