Seems like Wahoo doesnt log anything
I just looked over the datasets I’ve kept, and noticed something interesting. In nearly all of the Zwift rides I’ve done, the power difference corresponds almost exactly to a drop in virtual speed to around 15 km/h or less.
For example, when hitting the bottom of Alpe du Zwift, although my power at that point doesn’t change that rapidly, the power difference develops at precisely the moment that I slow down to climbing speed. Same thing can be seen beginning an ascent of Ventoux, and in a recovery session in NYC (at around 20 minutes; again, no significant change in power output here).
This makes me think it has something to do with the speed of the KICKR’s flywheel.
As for ERG mode, this is all done in one gear, so there’s not much change in the flywheel speed there. However, you’re supposed to do it in a low gear, and therefore with a low flywheel speed, which could explain why it’s commonly seen during ERG mode workouts.
Has anyone else observed this pattern?
Yep… exactly this with the initial release firmware. But it wasn’t virtual speed, it was the flywheel speed being <20km/h… (which usually correlates to low virtual speed) . This was addressed (mostly) with recent firmware updates.
What version of the firmware are you on?
Huh, interesting, did not know that. Guess I should’ve done my research before buying Still, I’m on the latest firmware (4.2.1).
Having read DCR’s report on this, it looks like the KICKR was originally over-reporting power, while here I’m seeing the opposite.
When you say “mostly” fixed, are there still known issues?
I think the drifting is a different issue to the cadence issue that was present in the initial firmware.
Drifting seems more dependent on the temperature of the trainer.
Right, but at this point I’m not sure which is which… At least in the data I’ve collected, you can view it both ways. Most of the hard efforts I do that might cause heat-drift are either in ERG mode in a low gear, or going up a steep hill, both of which also have a slow flywheel. So these conditions are themselves correlated.
I’ll try a flat TT some time this week (high power, fast flywheel) and see what happens. Another thing I want to try is pointing a fan at the KICKR’s flywheel to help it cool.
Add me to the list of the afflicted, lol. From what I’m seeing, higher power = more drift.
OK, today’s test was a 60 minute flat TT in Zwift, again in sim mode. The goal was to get the flywheel spinning pretty fast, but at a sustained high power output.
Pacing issues aside, the power matches damn near perfectly – the difference is less than 1 W over the duration of the effort. With 60 second smoothing, it looks like this:
P.S. Please ignore the device names that DCR Analyzer reports – they are the wrong way around.
zwift.fit contains the power meter data and
elemnt.fit contains the KICKR data (unlike my previous datasets).