Since the April release of Zwift I’ve been having very bad experiences with ERG mode. In March everything was fine, but since the April release it feels as if I’ve been fighting an algorithm that reacts to the cadence and that is trying to force my cadence down to about 85 RPM, regardless of the cadence target in the interval. The cadence that feels right for me is also a bit highter (something like 93-97 RPM), when I increase my RPM it feels like the power increases (this is not displayed in Zwift) which forces my cadence down. I can’t really prove this since Zwift is not displaying the power spikes and I don’t have power meter pedals to have a secondary power measurement source. What did change is that up until the March release the power during workouts in ERG mode was super smooth (always a nice flat line at the target power), since the April release this is no longer the case, the power instead oscillates around the target power. Note that I’ve always had power smoothing enabled both in Zwift and on the trainer itself.
I mentioned this once in an unrelated support ticket and then Zwift told me to update my trainer firmware to the latest version and that it would get worse in the future if I did not. I was using a Wahoo Kickr v3 with the latest available firmware version installed (the more recent version is not available for the v3). So I though it might be related to me using older hardware (that was still working just fine btw). A few weeks ago I upgraded my hardware to a Wahoo Kickr v6 and Zwift Ride with virtual shifting. I kind of expected the problem to magically disappear, but alas that was not the case.
Tested on:
Kickr v3 on Apple TV: Problematic since April
Kickr v6 with Zwift Ride on Android: Same issue
Kickr v6 with Zwift Ride on PC: Same issue
TL/DR:
There’s an issue with the power algorithm in ERG mode. It feels like it’s increasing power in reaction to an increase in cadence or maintaining a constant cadence about 90-ish RPM for more than half a minute. This happens EVERY SINGLE TIME I am using ERG mode.
I can only conclude the issue is caused by Zwift. It happens on multiple versions of the Wahoo Kickr, on multiple platforms. And there was no Kickr firmware update at the time the issue started appearing.
The only evidence I have is that power started to oscillate slightly around the target at the same time the issue started occuring instead of being perfectly smooth on target as it were until the issue.
This whole thing has made my Zwift experience a lot worse and has been having an impact on my motivation. Especially now that I have invested in a completely new setup and the issue still persists.
Thank you for posting! I am Nelson from Zwift Support.
I appreciate the detailed description. We recently launched a new game version (1.94.0). Please update your app and let us know how it feels with ERG mode on.
Feel free to contact us at Zwift Support, and we will be there for you.
Virtual shifting is disabled during ERG mode, so it’s probably a different issue. I haven’t noticed abnormal spikes yet during free rides where I used virtual shifting.
I tried a workout today after updating to v1.94 and I did not notice any significant difference. It was a rather hard workout on tired legs though, so that may have also affected how things felt today.
yes correct, VS is disabled during erg mode. I raised it only as you mentioned you also upgraded to kickr6 recently (same as me) and also started using VS (same as me) so I see the common denominator with issues is the use of VS.
I’m using the play controller that are integrated in the zwift ride. For me the issue did not first appear when I upgraded to the v6, it’s been there for months with the v3 already.
I recommend testing ERG mode in some other app. Shut down Zwift and run the Wahoo Fitness app, set the trainer control mode to Target Power. Does it feel the same?
I wonder if this is related to the relationship between the physical gear size and flywheel speed. But if that’s true then it should be the same in the Wahoo app.
Since you are using a Zwift Ride (right?) then another possible test would be to put a normal bicycle on the trainer and test how it feels when you use ERG mode in a relatively small gear and then a relatively large gear, since that will change the flywheel speed.
If Zwift support isn’t helpful then I would go straight to Wahoo support and try again.
Connect my Kickrv6 to Zwift as power source using the direct connect LAN module
Connect my Kickrv6 to the Wahoo fitness app on my phone with bluetooth
Use trainer control mode in the Wahoo fitness app to do 10 minutes warmup, then a constant 280 Watt for 50 minutes, followed by a couple of minutes of cooldown
As always, dual record with my assioma pedals on my garmin watch
It did feel a lot better than ERG mode in Zwift, but it still did not feel entirely right at times.
I put the data in the ZwiftPower analysis tool, it should be public: ZwiftPower - Login
If that is the case, shouldn’t everyone who’s using a Kickrv6 with Zwift Ride experience this issue?
I am indeed using a Zwift Ride. But I don’t have a different bike available at this time for testing.
I should probably do that. I think I’ll do a similar activity to what I did today but with Zwift in control of ERG mode. To see if the data looks different.
This is an activity I put in the ZwiftPower analysis tool a while ago. It’s the Red Unicorn workout with Zwift in control of ERG mode: ZwiftPower - Login
Another one from a couple of days ago (Escalation workout, Zwift ERG mode): ZwiftPower - Login
(Note: I have power smoothing enabled on the Kickr and in Zwift, if I turn off power smoothing I often don’t get stars for intervals in workouts.)
Yeah and I’m not seeing that (although there are other discussions of unexpected resistance levels). It’s just that the description you gave of an ERG mode power target changing and it taking some time to settle into the new level made me wonder if this is related to the flywheel coming up to speed.
The other way to try different gearing would be to put either a cassette on the trainer or a 3rd party single speed conversion kit with something other than a 14 tooth cog, but my wonderings are too speculative to tell you to spend money on it.
With power smoothing on it’s really hard to compare the output of the trainer with the output of the power meter, but when you see a power spike at the start of a higher power target, that’s what I would expect to be associated with a flywheel speed change on the trainer. The second workout you shared has a lot more of those.
By the way, this scenario will not require those changes in flywheel speed in your other workouts because you are riding at a constant power level. Wahoo SYSTM has a 14 day free trial if you want to try executing a workout identical to the one in Zwift using another platform, and when you test in a Wahoo app that helps you when you talk to their support since they can’t point a finger at someone else.
Hi @GlennVL - Just having a look at this for you. Do you have any other devices connected to your V6 at the same time as its connected to Zwift? You mentioned about using the Wahoo App. This can cause interference. When you connect ONLY to Zwift does it still occur? Additionally, in your earlier messages you mentioned about cadence changes affecting power. Zwift does not change resistance because of cadence. You could disconnect cadence from Zwift to confirm it doesn’t affect resistance.
