Wide Power differences in Kickr V4 & Quarq power meter readings (58 TSS vs 80 TSS for the same 1:15 Endurance Workout)

Hi All -

Long time listener, first time caller.

Background: Experienced (10+ years?) MTB XCO/XCM & cyclocross & gravel racer with a spattering of good results across different disciplines through the years. In the past, have always subscribed to the ‘ride lots’ training philosophy (I know, I know) for the times when I could not be bothered with intervals, but then also used customized training plans for specific A events with 2-3 different coaches throughout the years where nearly all of my training was done outdoors.

Even while I was training with my coaches…and wasn’t necessariliy an active TR user, I would tune in to the podcasts on a weekly basis and found that I generally jive & agree with the science backed approaches and answers to questions so always thought that I’d end up giving TR training plans a go at some point.

And finally, as of a few months ago, the timing was right in my life to move most of my training indoors (I’m currently living in Denmark…i.e. cold…rainy…dark) and so with a long time horizon before I move back to NorCal and any potential events, I thought I’d give a TR training plan a roll and see how it goes. So in September, I put in potential A races in the TR calendar for April and June respectively (i.e. Moab Rocks Stage Race in UT and MotherLode Epic XCM race in NorCal) and see what TR spits out at me.

In short…it spit out SSBHV1 and SSBHV2 for basically the months of September, October & early November, followed by short power build HV starting now through early January (to start raising the ceiling I suppose), then return to a SSBHV plan for the late winter (get working on the floor again), then I believe a specialty phase as we get closer to my first A event.

Sounded great to me and just finished working my way through SSBHV1 and 2 and started Build this week.

Everything has been going great…except for one thing…from my first ramp test, I was suspicious that it was reading low (OF COURSE IT WAS LOW HAHAHAHA). But when I did my first ramp test and spit out a 280 FTP at me my first thought was “wow I know I have not been ‘training’ but that is quite a drop from ~350 in the early Spring and I have been doing tons of riding still” (i.e. 10 - 12 hours + unstructured doing things like a 900KM off-road bikepacking race around Denmark, and doing a few days bikepacking down the western coast of Sweden from Gothenborg to Copenhagen). But regardless, I trusted the test and went with it, and the first few workouts were incredibly easy…so I kept manually bumping my FTP up until I found that sweet spot (no pun intended) where the SSB workouts seemed to generate enough stress, but I could do them to all (SSBHV1 and 2) to full completion every time. The number I manually settled on was 320 FTP.

I do all my workouts in ERG mode (Kickr v4) into an iPad via bluetooth if that matters.

Finally my question/issue: Through these past 2 months of SSB workouts I’ve been suspicious either my KickrV4 + TR numbers were low…OR my outside readings were high (for outdoor rides, I have Quarqs on my MTB, gravel bike, and road bike…and they seem fairly consistent with each other outdoors). So today, when an easy 1:15 minute Zone 2 workout was prescribed, I decided to do a comparison where I turned on my Wahoo Roam, and had it record power from my Quarq, while simultaneously performing the TR workout with the Kickr in ERG mode as I always do…and it was shocking how different the numbers were!

For instance, the Roam was reading sometimes as high as 50 watts more than the number on the screen in the TR workout that was controlling the Kickr. Overall, the differences would bounce between 30 - 40 watts difference (i.e. higher reading on the Roam + Quarq) between what the TR interval said I was holding in ERG mode.

I calibrated my Quarq with my Roam before starting this workout, and I did a Kickr spindown calibration ~2 days prior.

When uploading to TrainingPeaks — My ‘Roam + Quarq’ file spit out 80 TSS whereas the TR + KickrV4 in ERG mode was 58 TSS. Quite the difference for just an 1 hr and 15 minute workout…whereas one said I was working mainly tempo / sweet spot zones, and the other was pure endurance. Each one was working a completely different energy system for the same workout.

I expecting some differences…maybe 20 watts from what I have heard…but as high as 50?

Which is to be believed? Which is the most accurate? After some reading, it seems like maybe I should use an outdoor + indoor FTP for workouts?

I finally just did some searching and read about PowerMatch (?) for the first time…should I be using that? I will look into that further…

Holy smokes this was a long post…if you read this far your watt / patience ratio is up there with the best!

Yes, use PowerMatch. Same power meter inside and outside, for the win.

I have a V3 Kickr direct-drive (2017 model) and the optical power meter is a bit disappointing. PowerMatch will fix the problem, because your recorded power inside will be from the Quarq. And since your outside power is coming from the Quarq, you have the same power meter for all workouts. Win.


Definitely use power match. I had a similar issue when I compared my Kickr Core against multiple Stages and a Power2Max PM and it read way low. I use Stages PMs on my road bikes and it blows up your whole plan and metrics if there is a big difference between indoor / outdoor readings. With powermatch I’m consistent across the board.

One of the things that interests me is that most PM vendors claim 1-2% accuracy, including the kickr core and the PMs I use. But when I’m seeing 10% differences that is way outside the plausible range if the kickr is reading 2% below and my other PM is reading 2% above. I don’t want to get into existential questions about the nature of reality, but if each device measures different power and they are outside the margin or error how does one determine what is the ‘truth’? I guess if I had a PM that supported calibration with a hanging weight and could get a calibrated weight that would be the easiest, but I do not. And I could still calibrate it wrong. It is easier to not over think it, use power match, and use the quarq PM.

This is also one of my concerns with zwift racing and dual recording. I have zero trust in the accuracy of my kickr core and wouldn’t want to enter a race where dual recording was required because of my lack of trust in the accuracy of the kickr. And I don’t want to drop 1.5k on a new, regular kickr or yet another PM just for zwift racing.

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Thanks Craig and bbarrera —- Thanks for confirming PowerMatch. I would have been using it from the beginning starting my TR plan a few months ago, but I don’t believe it was mentioned or suggested anywhere, so I just didn’t know about it (quite possible I missed it somehow of course).

So now my question is: My next workout is tomorrow…the second ‘hard’ workout I have in the start of my build phase, and it is Fang Mountain +3 (a bunch of VO2 jobbers over unders I think). If I’m going to start using PowerMatch, should I do a new Ramp Test but with PowerMatch enabled?

Also - Today, as I recorded a 58 TSS workout via TR + Kickr ERG and an 80 TSS workout via the file generated from my power meter readings on the Roam. Which one is ‘real’? Which workout do I keep and which do I throw out?

Yes, in general you want to do a ramp test (or other FTP test) when switching to a new power meter. Turn on PowerMatch and ramp test away.

A good FTP estimate is perfect for setting workout intensity at aerobic endurance (zone2), tempo, sweet spot, and threshold. However VO2 and anaerobic workout intensity is more individualized, so it may or may not help with Fang Mountain +3.