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:

Threshold
Interval with 36x23

Interval with 52x16

VO2
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.

Thanks!

Found some answers here: https://m.youtube.com/watch?feature=youtu.be&v=_Pji1uAu_Us

1 Like