Is my new 4iii powermeter reading low?

Triathlon Forum
1

I bought one of the new 4iii powermeters. I’m worried about the accuracy. It seems to be low in steady state riding, but then over/under shoots with accelerations.

I did a short ride on my smart trainer recording the trainer on one garmin, and the 4iii on another. The average for the 4iii was 223 vs 232 for the trainer, around a 4% difference.
I then did a similar ride on the smart trainer with another bike that has a quarq I’ve had for years. The average for both the quarq and the trainer were 211 watts.

I had warmed up the trainer first and done a calibration. I calibrated each powermeter before the tests. My left/right balance is generally 50/50 on rides with a dual sided powermeter.

I’ve attached a screenshot of comparison files for each. Should I be worried about the 4iii?

Powermeter test.jpg

2

How do you know you have 50 50 balance? Is that based off the trainer and quarq? (as they don’t / can’t actually measure that and so provide estimated split based on algorithms).

And the surprise for me in that data is that the quarq isn’t teaching lower than the trainer as there should be some losses. So my guess is that the trainer is reading a fraction high and the quarq and 4iiii are within the 1.5% error range.

Either way. The differences you are seeing are not going to be significant in real world.

3

Which 4iiii meter is it? Single sided?

4

It’s a Precision 3+. Single Sided.

Acknowledging it is possible it’s down to left/right balance as the best guide to this is that when I’ve used powermeters that give a balance I’m generally 50/50.