Wahoo Kickr vs Vector 3 - calibration issues

radhartgeorge

Hello all,

I recently purchased my first power meter (Garmin Vector 3 pedals) with a view to getting into TTs in 2018. My winter training has been going well with a fair amount of workouts done on my Wahoo Kickr (version 1) and Zwift. Out of interest, I thought it would be good to test the accuracy of the Kickr and Vector 3 pedals by running them at the same time. The result is that my vectors were displaying lower power readings than my Kickr.

To address this, I re-calibrated both the Kickr (via a spindown within Zwift) and the Garmin Vectors (via the calibration option on my Garmin Edge 820) which improved things slightly but still left a 10-30W difference - increasing as my power increased.

Has anyone else discovered the same issue and are there any recommendations of how to calibrate them such that they are the same - I'd like to avoid having to do mental calculations and adjustments while making serious efforts in TTs.

Thanks all.

Flâneur

You are unlikely to get the same readings from two devices. Do calibrate each time and just focus on 1 power output (go with the pedals as you'll use them outside).

Check out the power meter accuracy results here https://www.dcrainmaker.com/2017/11/gar ... eview.html . The graph shows the data and there is a comment regarding a Kickr

Htclee

I’ve seen quite big disparities between the two, mostly at the start of a workout. The kickr needs a good 10/15 mins to warm up before calibration. Once calibrated you should find both are pretty close - within 5 watts or so. The next workout you do you’ll likely find that the readings are way out for the first 10/15mins but then move back closer together during the session.

radhartgeorge

Does this mean I have to re-calibrate the Kickr 15 mins into a cycle? If so, how is this done without ending the workout and beginning a new one?

Htclee

In Zwift you can simply pause your current workout, go to the menu then devices and use the wench symbol to run through the calibration. When complete you jump back to your ride and hit play to continue the workout.

saftlad

Are the differences not to be expected though?

The pedals are at point of contact, and the Kickr after drivetrain losses. I would have expected some level of disparity since you are not comparing like with like.

radhartgeorge

Having spent the last week undertaking fairly rigorous analysis I have concluded the following:

Initially, when cold (10 degrees Celsius) and calibrated there is a difference in power measurement (3s average) between the Vectors and the Kickr with the Vectors recording approximately 10-25% less than the Kickr.

As the Kickr (and potentially the Vectors) warm up from use the difference gradually reduces such that at the end of a fairly intense workout of approximately 1 hour and after re-calibrating both meters the differences in recorded power are negligible (+/- 2%).

I have yet to establish which power meter is to 'blame' for such deviation or if both power meters are responsible for the shift but in opposite directions. For this I am hoping to obtain a borrow a second Kickr and/or set of Vectors.

To answer Saftlad - your point about the differences being expected had occurred to me but would make more sense if the measurement at the pedals were higher than the measurement at the cassette but it's actually the other way around.

Elfed

radhartgeorge wrote:

Having spent the last week undertaking fairly rigorous analysis I have concluded the following:

Initially, when cold (10 degrees Celsius) and calibrated there is a difference in power measurement (3s average) between the Vectors and the Kickr with the Vectors recording approximately 10-25% less than the Kickr.

As the Kickr (and potentially the Vectors) warm up from use the difference gradually reduces such that at the end of a fairly intense workout of approximately 1 hour and after re-calibrating both meters the differences in recorded power are negligible (+/- 2%).

I have yet to establish which power meter is to 'blame' for such deviation or if both power meters are responsible for the shift but in opposite directions. For this I am hoping to obtain a borrow a second Kickr and/or set of Vectors.

To answer Saftlad - your point about the differences being expected had occurred to me but would make more sense if the measurement at the pedals were higher than the measurement at the cassette but it's actually the other way around.

That's exactly what I've found, but Vector 2 instead. First 10/15 minutes the Kickr is a bit optimistic but after that they're very close.
I believe it's the Kickr that's changing and not the Vectors.

I have my Kickr paired to Zwift and my pedals to my Garmin.

Wahoo state that there's no need to calibrate every ride, it should keep it's calibration unless moved.

stueyboy

Can you powermatch the Kickr with the pedals? I don't use Zwift but in Trainerroad, you can read the power from the pedals and then the software will tell the kickr to match it.