I have now replicated this bug on multiple Kickr Core units within Zwift (including one brand new unit out of the box). I can send video if necessary, but it should be easy to confirm. I don’t have access to any other models of smart trainer, or dual power recording, but at this point I am pretty certain it is a Zwift bug related to something within the virtual shifting mechanics.
I am using a single speed bike. I have a large chainring (60T) and a large cog (20T) with virtual shifting enabled.
If I am pedaling at a moderately high cadence 80+rpm and then I stop pedaling, my wattage in Zwift will initially drop to zero. However, as I continue to coast, after about 1-2 seconds, my Zwift wattage will jump back up to between 20-40 watts and my recorded cadence in Zwift will increase to ~90rpm, then 100, then 110-120. Both the wattage and cadence will stay this way for approximately 10 seconds, sometimes longer, even though I am not pedaling, before finally dropping back towards zero.
I’m wondering if maybe this issue is caused by having an unusually large chainring/cog combo and the way the virtual shifting calculations are done? Just a guess. I did not have this issue when using my normal road bike with the same trainer.
I do not believe this is a Wahoo bug because for the first couple minutes when I first set up the bike and trainer on Zwift it will not do this. It is only once the first virtual shifting autocalibration within Zwift occurs that it starts to take place.
I have tried doing spindowns (both basic and factory spindowns) within the Wahoo app, and it does not fix the problem.
My wattage and cadence generally seem correct when pedaling. It is only when coasting that things get out of whack (it also makes it impossible to super tuck since when I am coasting Zwift is still recording me as pedaling at 110+ rpms, even though wattage is very low).
First, I really like the old school notion that a 20t cog is ‘large’
Are you shifting when any of this is happening (doesn’t sound like it)? Have you tried not connecting your virtual shifting gear (Click or Play) to see if it happens then?
FWIW, this is something (or something similar) that I and other Saris H3 riders notice. Mine doesn’t go down to 0 and then go back up, but my wattage takes a lot time to zero out. It drops to more or less meaningless numbers (20w) pretty quickly, but stays there for a while. No virtual shifting here. I don’t get your cadence issue though.
Do you happen to have any new information regarding this? As of September 2024, this is still an issue - and I suspect that it is more prevalent than a few people. I have a kickr v6, and everything was absolutely fine before I installed the cog v2 and went to the zwift ride. This is not a trainer issue, rather it is an issue that appears more related to virtual shifting and/or the interaction of hardware/software - with the trainer and cog, combined with the game. A YouTuber was recent accused of cheating, getting “free watts” and after watching his video, I grew immediately paranoid about my setup - so I threw my Favero Assiomo Duals back on, and I did a few tests. The results are terrible. Long story short - I was getting 35-40 watts higher from the trainer/virtual shifting, than the power pedals. I did a factory spindown and this immediately fixed the issue, however, it appears that the same thing is beginning to happen again, albeit not nearly to the extent that it was. I truly do not think this has anything to do with the trainer, because I had been consistently dual recording rides for the last 18 months with my kickr v6 - I never had a single problem until I purchased the Zwift Ride, installed the cogv2, and starting using virtual shifting.
I do not have any new information. I’m still experiencing the issue ever time I ride. Zwift seems to be ignoring the issue or suggesting it is a trainer calibration problem. It is not. I personally have replicated it on multiple Wahoo Kickr Cores and others have had reported the same issue on other trainers.
I think you are exactly right, the issue is something to do with the virtual shifting.
I don’t have the ability to dual record but Im afraid I’d get similar results to you.
A user posted on this issue back in April. There was recently a YouTuber accused of cheating (edit: they actively use the bug, even knowing about it), and I am almost certain it is related to this issue.
I recently purchased the Zwift Ride and installed the Cog v2 on my Kickr v6. Prior to this, I had been using the Wahoo Kickr v6 for about 18 months, and I dual recorded about half of all my rides with Favero Assiomo Duals. The power metrics between the Kickr v6 and power pedals was almost identical. I have a significant power imbalance between legs, due to nerve damage from back surgery, so I appreciate having pedaling dynamics from the power pedals.
I recently was promoted from Cat C to Cat B, and I was having PRs all over the place - from 1 minute all the way to 2 hour power output. Ignorantly, I thought I was really hitting a new peak - until I came across the video of the YouTuber accused of cheating. It was during this video that I became paranoid that something was going on with my data - so I put my power pedals on the Zwift Ride and did a quick test. The results were awful. The average power on the Trainer with virtual shifting was between 10-15% higher than the power pedals. This is not even remotely close, or acceptable. I then just started to pay attention to what happens when I stop pedaling altogether, after building up to a decent power and cadence. Upon stopping the power will initially drop to zero, but then the watts go up - in addition to the in-game cadence. Not pedaling at all, the watts then stay at 25-40 watts, RPMs up to 110. Overall, my dual recorded test ride resulted in an average power variance of about 35 watts - this resulted in a significant difference in distances, and skewed everything. I came across a Reddit thread that highlighted that this issue is related to virtual shifting, and recommended a factory spindown - after doing this, everything was completely normal (and accurate). However, since doing the factory spindown, the problem appears to be creeping back - but not nearly to the extent it was initially. In addition, the Reddit thread mentions that the problem occurs only between gears 22-24 in virtual shifting, however I believe that it is a problem no matter what gear - as I haven’t even hit 22-24, and the problem is coming back.
The post from April didn’t have any resolution. It seems very unlikely that I am the only person experiencing this problem as well.
You aren’t alone, I’m experiencing it as well. I just created a new topic about it. I feel ignorant. I thought I was hitting new PRs - and it was related to this bug/problem. I agree, it isn’t a trainer issue at all.
Question 1: Are your Assiomas paired to a GPS head unit or to Zwift? They should be paired to the head unit, same as you’d do outdoors. Your KICKR should feed power data to Zwift.
Question 2. Is your GPS head unit adjusting the Assioma’s readings for the crank length? If no - that can skew your power numbers considerably. The pedals have no idea what length cranks they’re installed on - the conversion of torque to power happens in the head unit or Assioma app, and the crank compensation happens during that conversion.
My power pedals are paired to my Garmin Bike Computer. I’m not sure about GPS head unit adjusting for the crank length. The primary issue isn’t really the Power Pedal accuracy/Bike Computer - it’s that it appears I’m getting a bump in watts from the Kickr v6 and virtual shifting. This is currently better after doing the factory spindown, but it also appears it is coming back. It is very noticeable when I stop pedaling - in-game the RPMs stay up, and the watts are not zero.
Check the settings for your pedals within your garmin, there will be a crank length element, default being 172.5mm. If you use your garmin to calibrate your pedals, the crank length on your garmin will be fed back to your pedals as part of the calibration, if that crank length is wrong your pedals will then be out. The free watts thing though is concerning…
I’ve been using virtual gearing on Kickr Move (which is a v6 on rails) for a couple of months, but not noticed any power drift from setting new PBs etc - I’d need a power meter to verify of course! Watching the thread with interest however.
If you run the trainer without virtual gears (e.g. no Play or Click controllers) so they aren’t active and the gear index-calibration doesn’t happen (I assume it doesn’t?), does that help with the auto-calibration (showing it’s using the virtual gears is the problem), or do you think that it’s because the trainer has virtual gear capability whether you use it or not causes the problem? Does it still have an auto-calibration problem if you do a workout in the Wahoo app?
I’ll also look out for the power bump when stopping pedalling on my next ride.
Once the issue was present, it didn’t matter if I connected to the Play controllers or not - watts wouldn’t go to zero, nor would RPMs. The only thing that helped was doing the factory spindown. I did not try doing a workout in the Wahoo app, but I’m willing to try (if the issue comes back - everything is still looking pretty good from the factory spindown).
Hey all - we’ve discussed this with our colleagues at Wahoo, and this is a known issue that will be addressed in the next firmware release for KICKR v6 and KICKR Core.
The short-term workaround is to perform a factory spindown test + power cycle to put the KICKR back to normal.
The really bad thing is, and something that I probably didn’t make clear - but everyone should understand, is that when the issue is present, even when pedaling, the “phantom free watts” is active. This is what really made me sick - I very seldom coast, it’s just easier for me to keep the legs moving. When I tested, my dual recorded rides indicated that my watts were being artificially boosted by the same watts - as what I was seeing when I wasn’t pedaling at all. So basically, anyone who has this happening is receiving a bump in overall power. I do understand your point though - yes, reverting back to the original state, after doing the factory spindown, not using virtual shifting - would definitely be a good way to prevent the occurrence, you’re right. I just wanted to make sure that it is understood that if a rider is currently experiencing what is outlined, that they are receiving a bump in watts - pedaling or not. It simply is most obvious when not pedaling - watching the rpms jump up to 110 or so, and watts go up to 25-40.
