Successful and very frustrating ramp test!

UPDATE
I’m wrapping up my Kickr Snap versus Quarq PM comparison. My results so far are that the Kickr is quite accurate (within 1-2%). On Taylor -2 today the Kickr and the Quarq were statistically identical:

2 Likes

Those graphs are so crazily close that it almost looks like the same power source, just with different sampling. My Favero and Neo are never anywhere near that close!

1 Like

I’ve noticed, still doing more testing, that higher cadences track closer between the two PMs :man_shrugging:. This workout was 100+ rpms on a 32 x 18.

Amazing, thanks for sharing this! I’m happy to see this information. Hope your happy with your quarq! I’ve heard great things!

1 Like

I agree with graytham. Looks like the same power source. Sorry, I’m not buying that a Kickr Snap can be this close to a power meter.

Ummm, ok, lol. I guess I’m a liar :lying_face:. I removed the smoothing from the DCR Analysis Tool and added the fit files. Maybe this will help with your “buy in”? :crossed_fingers:

1 Like

It’s ok! some people just don’t want to believe other people have big power numbers, or that other people can properly record power data. Thanks a lot for all the info!

2 Likes

My comments were based upon the data you posted in the first graph. You should have posted the actual data not the Wahoo artificially smoothed as my comments would have been a bit different. Not calling anyone a liar. Having had 2 dud Kickr Snaps and coming across many other people with similar accuracy problems it’s very hard for me to believe a Kickr Snap can be so close to a power meter. You’re fricken lucky to have got one that works as it should. Make the most of it. I’m very glad to have got a refund on my replacement Snap and bought something else.

BTW your Snap is more accurate than my Hammer trainer but it’s close enough. I use power match anyway for workouts.

I don’t think that anyone thinks that you’re lying! It’s just that I would be surprised by any two power meters tracking that closely. The best Snap in the world is still going to be a little bit affected by the differences between how it does things and how e.g. a Quarq does. If I got a graph like that from any pair of my power sources, the first thing that I’d think was “I’ve somehow accidentally recorded the same source twice”. But if you’re sure that you haven’t, then great - you’ve got an awesome Snap!

I didn’t post/use any smoothing from Wahoo. The DCR analysis tool allows you to apply smoothing to compare power files. To discover abnormalities when comparing these files it is recommended to use some smoothing (ie: 10 secs) so differences don’t get lost in the numerous data points. If you remove smoothing it’s difficult for comparison. The point is to ensure both PM track consistently, not that every 1 second sample is precisely the same, since the PMs may sample and report at different moments.

It’s near impossible to “accidentally” recorded the same power. TR is using the Kickr’s Erg and the Quarq is reporting to the Wahoo Bolt. The Kickr and TR doesn’t know the Quarq or the Bolt exists. The Quarq doesn’t know the Kickr or TR exists. Then you simply download each .fit file from the Kickr and the Quarq and load it into the DCR analysis tool.

1 Like

I was careful to phrase my point correctly (“the first thing that I’d think”). Please don’t be defensive (maybe you’re not, can be tricky to tell in text). It’s only near impossible to accidentally record the same power if you know how you’re doing that, and you hadn’t said (unless I missed it) how you were recording that previously. I have done similar things all kinds of ways, including using TR (connected to a particular trainer or source, but with past knowledge (i.e. pairing info) for others, certainly), and also multiple head units connected to multiple power meters, where those head units each know about multiple power broadcasters including the trainer itself. I do take care to disable the ones that I don’t want to record, and do pay attention to the data files (which record IDs of the sources), so it is indeed absolutely possible to be sure of what you’re looking at, but it’s also (based on the information you had given us) nowhere near impossible for someone to accidentally record the same power in some circumstances.

And I stand by my assertion that your data are crazy close for two power sources, and even more so for a wheel-on trainer. I had a Tacx Vortex which was light years worse than that - I could clearly observe the thermal effects within intervals. I was training in a very cold room though, so it would cool off markedly within each rest interval. I’m guessing you are in a warmer place, or else the Snap has much better temperature compensation.

I am in the process of doing a full analysis of Kickr Snap versus Quarq and intend to do an in depth separate post with all the setup details. That was not my intention when I posted. Rather people have suggested that the “wheel on” trainers were way off and users should expect a big drop in FTP when they get a “real” PM. My point was to show that’s not the case.

OK cool - that will be interesting. I can add my experiences with my Tacx Vortex (but that could be quite brief and involve swearing!). From mine and others’ experiences, I think my overall conclusion is that wheel-on trainers are more likely to suffer from differences from ‘truth’, and are more vulnerable to variability, but (a) direct drive in itself doesn’t guarantee an overall improvement (especially in training usefulness), and (b) careful understanding and use can often improve things, and © there’s at least one out there that’s amazing, but mine was not.

1 Like

That is probably all true regarding direct drive versus wheel on. I’m finding oddities when I change up gears and vary cadences…

Interesting - were you in erg mode for that test? It’s very hard to guess what’s going on without knowing which trace is which power source, and whether your were in Erg mode or manually holding a given power (e.g. from looking at Quarq data). Did you change gear to change cadence, or just let Erg mode do its thing?

On my Vortex, it would take a while (maybe 20 minutes) to get warm. During that time the effective calibration factor would drift as things get softer / less viscous. After then the effective calibration factor would be affected by both power output and wheel speed. In general, faster wheel speed => more fluid resistance => more heat build up and thermal drift (so Vortex would tend towards reporting higher virtual power). More power => more electrical brake resistance => more heat => higher reported power for a given true power.

Things didn’t always precisely follow that simple model, but I ended up concluding that most of the crapness that I saw with my Vortex was down to heat management / compensation. I don’t actually know if it has any active temperature compensation (i.e. other than just saying “warm it up before doing a spin down”). It was actually not far off my Powertap and pedals if I e.g. held a steady 200W for 20 minutes, did a spin down, and continued at 200W. Trouble is, even then my body heat would warm the shed up… :slight_smile:

Erg mode for all my tests, letting it do it’s thing. Red is Quarq and Blue is Kickr Snap Erg. Didn’t change gears in this test, only cadences. Using a 1x setup at 32 x 18. All tests are proceeded by a Quarq calibration and a separate Free Ride warm-up workout (about 115 watts) then a Kickr spindown calibration inside of TR. I’ve tried to isolate every variable to include temperature. Trainer is in my basement and temperature doesn’t vary more than 5 degrees day to day (about 65 degrees on average).

So the most interesting bit to me is what happens at 30 minutes…? The target power steps up, the Snap (obviously) thinks the delivered power has gone up accordingly, but the Quarq simply says “meh” - it seems to notice the spike (probably cadence change related as much as anything) but settles out at the same level as it was before.

If you ignored everything after that point, then things hang together perfectly - from say 5 mins up to 30 mins, as you decrease the cadence, the Snap reports lower power relative the to Quarq, which would be consistent with it warming up a bit relative to the lower intensity freeride portion, and with cadence effect manifesting directly through wheel speed. However, after 30 minutes things kind of go in the opposite direction! :thinking:

It’s all very odd and there are so many internal variables being adjusted by the Kickr Erg and the Quarq. In the end, the NP and Avg Power between every test workout so far has been within 0-2% difference. Which means within the margin of error of any power meter. So no matter what device I am using, Kickr’s Erg, Powermatch or the Quarq, I am essentially getting the same workout benefits in the end, even if the two devices may stray from time to time. I will continue testing, but my early conclusion is that;

  • If” you hold all variables constant, do daily trainer warm-ups, spindowns, PM calibrations, tire pressure checks, firmware updates (should they be needed), be completely OCD regarding setup;
  • Then at least in my case the Kickr Snap and Quarq are the same and inserting the Powermatch variable is not needed. Resulting in my ability to use the same FTP for inside or outside rides as well as continue to use the Kickr’s Erg for ramp tests.
1 Like