KICKR V5 power discrepancies

I’m new to smart trainers and I’ve been I’ve been enjoying both TR and Zwift since I bought a KICKR (my first trainer) a couple of weeks ago. But curiosity got the better of me and I decided to compare the KICKR with my trusty power2max Type S and I found that it’s consistently reading high.

For example, here’s a Goddard -4 I did the other day in ERG mode: DC Rainmaker Analyzer

The KICKR seems to track the p2m quite well, but is consistently around 10 W high.

And a chilled out Zwift session from today for some recovery (ignore the gap in the middle when ELEMNT paused itself): DC Rainmaker Analyzer

While the difference isn’t as obvious here (more like 5 W), but the KICKR’s readings are quite spiky and erratic in this case.

When I look at DCR’s analysis, it looks somewhat better behaved: DC Rainmaker Analyzer

Is this normal for a KICKR (or any smart trainer)? Am I just being too fussy?

P.S. I’m using the latest firmware (v4.2.1) on the KICKR.

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Sounds somewhat similar to the discussion in this thread:

Your Zwift/sim-mode workout seems fine to me, 5W isnt that much.

When I look at the TR workout, I see a couple of interesting things. Seems like PM and Kickr reads spot on between 4min and 8min (marked with yellow). It also seems like there maybe some power smoothing turned on in Wahoo app (marked with red).

I have had good success with doing a factory spindown post workout (when trainer is warm), my Kickr now reads very close to my PMs, but i still see som drift during a workout, most within the first 30-40 mins.

I would try a factory spindown and test more to see if you can find some kind of pattern. If you can it would also be great to test with an other PM too.

Thanks for looking :slightly_smiling_face:

Here’s today’s Ericsson session: DC Rainmaker Analyzer

This one seems a bit better behaved; the difference is consistently around 6 W this time, which seems more reasonable (ignoring the ITL bit at the beginning).

But the recoveries still look pretty weird. We’re looking at 10 W or so again, and the power from TR is clearly smoother… almost suspiciously smooth. I don’t have any kind of smoothing switched on in the Wahoo app, so I don’t know what’s going on there.

My plan for tomorrow’s session is to swap to a different power meter (power2max NGeco with 1% accuracy) and then do a factory spindown as daniebr suggested. Sadly I don’t have any pedals I can use at the same time.

I remembered that I also recorded last week’s ramp test on my ELEMNT as well: DC Rainmaker Analyzer

At the top of the ramp the two power readings match almost exactly – within 1 W, which is pretty excellent.

But at the start of the ramp I can see the same effect as with the recovery sections in the other sets:

The power from the KICKR is higher, and suspiciously smooth. @daniebr Is this something you’ve seen in your tests? Maybe an effect that’s only present at low power in ERG mode?

I guess I don’t care that much if it’s only happening during recovery…

My Kickr readings is smoother than my PM readings, but I dont see any difference in smoothing during recoveries. This is my newest set, as usual my Kickr reads a bit high in the start, accuracy seems better during intervals(high power) than during recoveries:

I’m also experiencing a strange issue. Brand new V5, up to date firmware. Last night’s threshold intervals, my stages Left side PM is consistently higher(I expected this and not surprised). For the most part they both track pretty well together, but at the start of the intervals it takes the power reported from the Kickr about 3 minutes to ‘ramp up’. Ultimately I’m not too concerned about it as I use the stages as my power source.

My Kickr readings is smoother than my PM readings

@daniebr Turn off power smoothing for the Kickr in the Wahoo app. It will look more normal after that, even in erg mode.

@Cory.Rood: You might have a similar pedaling pattern like me, Im allways pedaling harder on left side in the start of intervals, and it equalizes after a while, that would make a similar graph as yours if I used a single sided PM:

@rkoswald: My power smoothing is turned off.

Today’s Zwift ride in sim-mode: DC Rainmaker Analyzer

This time I was using a brand-new NGeco power meter with 1% accuracy.

Starts off bang-on, but by the end of the session the KICKR was reading 6 W lower. Not sure what to think now. I’ll try tomorrow’s ERG mode workout with the same power meter and report back.

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@daniebr Well, now it’s looking an awful lot like your drift problem: DC Rainmaker Analyzer

Again, starts off fine, ends up with the KICKR reading 12 W low. Interestingly, it starts precisely at the start of the first recovery.

I haven’t yet tried a factory spindown, but that’s my next step.

Really does sound like power drifting down is THE problem on the V5 - there had to be one.

If you read in the drift-thread, you see that I experienced some of the same “power jumps”. Seemed to happen when increasing cadence.

Went up Alpe du Zwift today: DC Rainmaker Analyzer

Exactly the same behaviour. Perfect for the first 10 minutes, then drifts right on up to 12 W, all the way up to the top.

Doesn’t seem limited to ERG mode.

I’ve tested my new V5 with a long steady state effort against my old set of Powertap P1 pedals and new Magene dual sided unit: DC Rainmaker Analyzer

Ignoring the efforts at the end where the Magene is looking problematic (there’s a thread about that elsewhere) I took a look at the the first 30 minutes (after the first 10, so 10-40m) and the last 30m before messing about at the end. Looks like it breaks down like so:
Kickr is 2.5% higher than P1 on average at the start, 1.9% higher at the end, which seems like a wash.

Is anybody seeing drift on long sessions, or is it mostly during shorter more intense intervals?

I see it over long efforts - most within the first 40mins though.

Exactly the same for me. Here is my latest test, an ascent of Ventoux in Zwift: DC Rainmaker Analyzer

The drift is very clearly visible here if you smooth it over 60 seconds:

I’m in conversation with Wahoo about this at the moment.

What made it go back to normal? Is that just after the descent? I.e. after it’s been allowed to cool back down?

Yep, I went back down at 150-200 W. I can only assume this allowed it to cool down, and that it’s the internal temperature of the KICKR that causes the issue.

Glad I’m not a pro with an FTP of a bazillion watts…

Make sure you let them know that there are a few people having this issue - when I briefly mentioned it to wahoo support they said that they hadn’t had any reports of similar issues…