Zpower fluctuating wildly on a Kurt Kinetic Rock and Roll T-016 trainer

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Hello! Long time Zwift user here - since the Beta days two winters ago.

I just switched from a TACX Sirius manual variable resistance trainer to a used Kurt Kinetic Rock and Roll trainer model T-016. 

I configured Zwift to use the Rock and Roll and ZPower mode for the wattage numbers however when I started my ride tonight my power numbers were all over the place by factors of almost 5X what they should be. 

After I noticed the weird numbers I powered up my Garmin 810 and based on the values coming direct from my GSC-10 cadence/speed sensor I was riding at a targeted wheel speed of 10 MPH however my ZPower numbers were ranging from the low 30’s to over 400 even though my Garmin was showing a steady speed of approximately 10MPH.

I replaced the battery in the GSC-10 just the other day and my USB ANT+ stick is attached via an extension cable so the sensor is directly under my bottom bracket.

See the two events here:

https://www.strava.com/activities/861952860 => Garmin ride (which has the last mile or so of Zwift)

https://www.strava.com/activities/861953082 => Zwift ride 

Any ideas why the numbers fluctuate so much? I don’t want to have to go back to the old TACX but at least using the Classic unsupported trainer mode I was getting consistent numbers.

Thanks!

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You’ll want to start with going through our setup expectations; if any of these factors are different, they’ll affect your readings. I see you have a ticket open with us, so we’ll work with you on the specifics there.

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Hi Jason - it is looking like it is the speed/cadence sensor that is the issue. I swapped out USB/ANT+ dongles, tried my old TACX trainer, even swapped out the laptop with a totally different one all with the same weird results. I also ran a quick install of Golden Cheetah and sure enough I am seeing rear wheel speed spikes using that app as well.

Thanks for the help - I have ordered a replacement speed/cadence sensor and will try that as that is the only piece of the puzzle that I haven’t replaced.