Virtual shifting prevents autocalibration on KICKR Core?

The KICKR Core does not have 10Hz power reporting (aka “race mode.”). That is available on Wahoo’s more expensive trainers.

I’m usually pedalling at 85-90rpm and wonder if I have a power imbalance in my legs causing interference with the virtual shifting power measurement? When in ERG mode or manual mode power is smooth and calibration in the wahoo app does not help with the power wobble.

Does it matter whether the small or large chainring is used for virtual shifting? As long as it’s a comfortable starting position in gear 12, presumably the rider generates the same watts from the trainer based on effort applied? Assuming the rider outputs the same average wkg, would it mean that the only difference at the end of a ride is average cadence? Or will any given rider find it harder/ easier with the two chainrings?

It would be interesting to get an official response on this.

Watts are watts is usually the argument given. But power is a product of torque applied at rpm.

A rider does not apply power. They apply torque at a given rpm which produces power

The difference between small chain ring and large would be flywheel speed and momentum.

Applying torque at higher flywheel speed has been shown to use different muscles. This could be beneficial, or not, depending on the rider’s physiology.

In addition, there would be less drivetrain loss from using a larger chain ring.

I am seeing this power wobble or oscillation as well with Zwift Play virtual shifting. I am on a KICKR core (FW 1.4.8) with a Macbook Air M1 (Sonoma 14.4.1). I have a cassette on the KICKR and the one thing I can add is it seems to matter what physical gear I am in. Some physical gears do not have the oscillation/wobble (or at least it is greatly minimized) and some do. I tested this by unpairing in Zwift Play, changing the physical gear, and repairing. Cadence, course, and trainer difficulty do not seem to matter. I am happy to do more testing.

Sounds interesting. Which gear are you in?
Zwift Cog has 14 tooth. Need to check how many I’m using.

36x15 works OK but 36x17 shows the wobble!

Thanks. For a straight chain line I’m using 36x17, too. Will double check later your investigation

I have been trying different cogs on both the small and large chainrings. I haven’t found a cog that eliminates this power fluctuations, but I do find the larger chainring slightly more stable and closer to the regular shifting experience. However, in all cases, virtual shifting requires significantly more effort to achieve the same power output as regular shifting. I don’t have a second power source to prove the different power reporting by the trainer, but having followed the same pacer on the same route with a similar small group each day, I can clearly see (and feel) a major difference in heart rate stats and stress info on Strava.
Combined with the Zwift Play steering and braking functions being so close to the shifting buttons, I’ve decided it’s probably easier to stick with regular shifting until at least the power reporting thing is solved.

I have experienced the same but thought it was just me having a bad day. I don’t have a additional power meter to check the facts either.

I am experiencing the exact same “wobble/oscillating” issue as above.
Equipment :
Power Source : Kickr Core ( firmware version 1.5.5 2024/03/15 )
Cadence Sensor : Kickr Core ( firmware version 1.5.5 2024/03/15 )
Resistance : Kickr Core ( firmware version 1.5.5 2024/03/15 )
Play Controllers ( firmware version 1.3.0 )
Connection Type : Bluetooth
Zwift : Instant Power
Wahoo: all defaults ( no power smoothing applied )

Test Protocol :

ERG Mode : No Issues, power is maintained smoothly
SIM Mode : ( Physical gearing maintained 36/14 )
Average Cadence : 85-95
Low Power : Seated, 85-95 cadence, 180w - 250w Power reading oscillates with a constant frequency ( -+30w either way )
High Power : Standing, 60 -70 cadence, 400w - 500w Power reading oscillates with a constant frequency ( -+50w either way )

Observations :
I have noticed that this behavior is erratic. Sometimes I never experience it. Sometimes it appears mid-ride. Sometimes it is present from the beginning on the ride.
I have noticed the cadence fluctuate between 0 - 50 rpm (on occasion) when sitting stationary on the bike ( i.e. 0 rpm )
Once I start pedaling it then rectifies itself and seems normal.

Below is an example of Attempting to hold 300w steady. ( you can see it is behaving the same at all power levels )

This is the “normal” graph example

2 things that strike me :

  1. The pattern is repeating at a consistent rate ( indicates a calculation happening every X seconds )
  2. I have a feeling it is cadence related as cadence is required to calculate power. If that is oscillating, so will the power reading.

Hope this helps

It is interesting that you see the behavior come and go. In my case, if I am in the “wrong” physical gear, the oscillation is always present. I am on KICKR Core FW 1.4.8 (3/5/24) though which I thought was the latest? Definitely seems like a bug that needs fixing…

I think you are correct Willa. If I start the ride and the oscillation is NOT present, then change the physical gear it starts.
However, sometimes it starts from the outset ( when remaining in the same physical gear ), which leads me to believe that Zwift does some sort of calibration on startup and sometimes “gets it wrong”.
Either way, if it start out with the oscillation I can often change the physical gear to one that seems to work and then continue in that gear for the rest of the ride. Not perfect, but good enough for now

I wonder if the one-time virtual shifting calibration described by Shuji earlier in this thread sometimes doesn’t complete successfully, or the process continues longer than expected, or it sometimes succeeds later after a gear change. If that were the case though, I would expect correct readings when virtual shifting is not enabled.

Same issue. Wahoo kickr core. Newest firmware, 3 sec power, 50% diff. Described this problem in bugs section - subject - kickr core virtual shifter bug (added tests, screens and power wobble data)

Its impossible to maintain steady power with virtual shifter ON. No matter power, cadence, race, ride, going up, down, flat… It just jumps. Only erg is working properly.

Forced me to put virtual shifter aside. Its bugged and its frustrating experience. Hope we will get this fixed.

See above…