Power Drift (Kickr on Trainerroad vs Garmin reading Stages Power)


#1

I have a 3 week old Kickr and I have yet to have ERG more work for me correctly. Everything is calibrated and paired. I have done this multiple times as well as deleting and reinstalling TR, re-pairing devices etc. TR is the PC app using ANT+ and I record the Stages for comparison on a Garmin 520. TR is paired with the Kickr and the Stages but for cadence only. I did have the Stages power driving the Kickr output (after having to borrow an iOS device) but had even worse results.

I am seeing a distinct drift between power reading over the course of a ride. In the beginning the Kickr and Stages power track close to each other, never varying more than a few watts when riding smoothly. Later in the ride there is a consistently higher reading from the Stages power when compared to the Kickr output on TR.

Any suggestions how I can reduce or eliminate this drift? Is my Kickr faulty? What are other people seeing for drift over the course of a ride?

TR power required - 168W
Early ride Kickr readings (13 to 15 min) average 168W
Early ride Stages reading (12:59 to 14:59) average 170W


TR power required - 170W
Later ride Kickr Reading (50-55min) average 171W
Later ride Stages reading (50:01-55:00min) 182W


#2

It is very common for your power meter to differ from your Smart Trainer, especially as things heat up and the resistance changes slightly. In fact, it is so common we built a tool that allow you to use your physical Power Meter and ignore the power reading from your KICKR entirely. This feature is called PowerMatch.

You can learn more about PowerMatch in this article:

Cheers!


#3

I was unable to get Power Match to work through TR. Wahoo only provides the ability to link the Kickr and a power meter through iOS app, not the Android app. Without the pairing I was unable to achieve any ERG mode like results. Even after borrowing an iOS device I still had no luck.

Almost every power meter has temperature compensation built in. Do smart trainers not account for temperature drift as well?


#4

Trainers do not autocalibrate unfortunately :pensive:

For optimized power, you should calibrate about 15 minutes into your workout so that the Trainer is properly warmed up upon calibration.

May I ask what went wrong with your PowerMatch? Our Support Team should be able to help you get things up and running properly. You can send us an email at support@trainerroad.com.

Cheers!


#5

You can pair your kicker with your power meter and just let the power meter tell the trainer what power it is putting out.


#6

Is this a left-only Stages? Just mentioning that legs (may) fatigue differently. Mine do. The right leg fatigues quicker, e.g. over the course of a ride a one sided stages overestimates actual power output.

However, don’t know what the current Kickr models show with regards to drift but I don’t remember seeing anything in the reviews by dcrainmaker & co. My old 1.gen Kickr drifted quite significantly


#7

Now that I have re-installed everything I will try Powermatch again and let you know how it goes.

If smart trainers drift with temperature (in my case above, 6.4%) how can they claim +/- 2% accuracy?? I’m tempted to go back to using my e-motion rollers and shifting gears to match the power levels in TR.


#8

Typically what they claim is that if you calibrate after warming up the trainer (ride 15 minutes, stop, calibrate) then you get their accuracy claims. The drift should be minimal or non-existent after the warmup is completed.

That said - I’d strongly recommend using power match


#9

The suggested 15min warm up then spin down calibration gives me excellent results (+1W) comparing Wahoo in TR to Stages on Garmin in the same time frame but not over a longer period of time. I “warmed up” at 170W. What would happen if I warmed up at 280W? Would that result in a higher temperature and a different calibration point? With different input or different time to warm up I’ll get a different calibration value. Will it ever reach a steady state temperature? I can’t believe the Kickr does not have temperature compensation. How can they claim +/-2% accuracy without it?

I am going to try Power Match now. If it fails to work this time I think this thing is going back.


#10

The power at which you warm up the trainer doesn’t matter. It is truly a matter of warming the temperature of the machine and the calibration spin down is identical regardless


#11

I’ve had Kickr 2017 + Stages left-only power meter for a year now and it has generally worked well using:

  • Kickr power only (Stages as cadence)
  • Kickr with TrainerRoad PowerMatch (so that inside and outside power readings match)
  • Kickr with “Control with ANT+” (Wahoo’s version of PowerMatch)

I’m using TR on iPhone, so Kickr and Stages are connected via Bluetooth.

On Sunday I finished upgrading to Stages LR and also replaced pedals. Was on the road for 5 hours yesterday, and did a short trainer ride to “settle in” the pedals and PM. The “Eclipse” workout was on my calendar and I only did one interval. It felt a lot harder than usual on a 94% interval, like I was at threshold and not sweet spot. Hmm…

Like you I was dual recording with Edge 520 and TrainerRoad app (using Control with ANT+ option from above). During the sweet spot interval the Edge 520 was reporting ~15W higher than TR app. Sure enough, after uploading both to DCRainmaker’s analyze tool I could clearly see the difference.

After ending that 35 minute shake down ride, used Wahoo app to do a spindown and then an advanced spindown. Using Stages app did yet another zero reset. Then a 2 minute and 1 minute test where it was within a couple watts.

Going to ride tonight and if same thing happens, will disable “Control with ANT+” and go back to using TR’s PowerMatch. Theoretically the Stages left pedal is transmitting total power to TR over Bluetooth, so it should work just fine (as in the past, before upgrading to Stages LR).

Both Stages “Control with ANT+” and TR’s PowerMatch should result in using Stages for power both inside and outside. I’m a little surprised that “Control with ANT+” wasn’t working well yesterday, given I’ve been using it for the last month. The good news is that TR wasn’t involved its just the Kickr and Stages so I can pursue resolution directly with Wahoo if it happens again tonight.


#12

I set up TR with Powermatch so the Stages power was supposed to be controlling the Kickr output. It did in fact track well between the two readings but I’m not impressed if this is how ERG mode works.

I did two short rides, one at lower power and one with a few intervals at double the power. Do these curves look typical while using Powermatch? I found on the 300W intervals the power seemed to fall below target and I had to steadily increase cadence to attempt to maintain power.

Is this the way its supposed to work or am I just expecting too much from ERG mode?


#13

Looks reasonable to me. If you are like me, then smoothing out pedal stroke and using a steady cadence somewhere between 90-95rpm will give less power fluctuations.

Look at this post and the one immediately following for examples of what I’m seeing: PowerMatch Experiences


#14

Thanks for the link. Those curves do look a little smoother than mine.

Maybe the Kickr just doesn’t work the way I’d like. I’m coming from a few seasons of TR using Stages power while on E-Motion rollers matching power using gearing and cadence. It was certainly more work mentally to track the power curves on the rollers. I was hoping the Kickr would help with that but it’s just been 3 weeks of frustration.

Typical TR graph from Stages and E-Motion roller ride.


#15

that looks more like my power fluctuations on Kickr, in Erg, using any of the different control options (Kickr’s integrated optical power meter, TR PowerMatch, or Kickr Control w/ANT+).

I don’t use Windows in general, so no experience with TR app on Windows.

The radios in Stages are known to transmit at lower power versus other power meters, and therefore I have experienced ANT+ dropouts on TR before a) using USB extension cable with MacBook Pro to place Garmin ANT+ dongle near crank, and b) switching to Bluetooth.


#16

Have you tried an Advanced Spindown? You have to tap the spin down text 5 times to enter into Advanced Spindown mode: https://www.smartbiketrainers.com/advanced-spindown-calibration-wahoo-kickr-snap-4350


#17

Unfortunately I don’t have an iOS device and Wahoo decided that a defeatured Android app was acceptable.


#18

read the 2nd to last comment on that article for Android instructions on performing advanced spindown.


#19

I think we both are expecting too much. I just came from a Kinetic Road Machine. I did a few hard efforts on an ERG mode steady state workout this weekend and TR stopped a few times because I didn’t want to hold 120rpms after a form sprint. Just takes some getting used to coming from rollers or a wheel-on.

I’ve had many recommendations to use the Kickr only in resistance mode. In theory, it would eliminate the floats after hard efforts. Going to do my first “real” workout tomorrow AM. Plan is to be in resistance the whole time.

I have the same variances with Stages vs Kickr Core Power. Was going to do a Ramp Test using the Kickr power and sell my Stages, but stopping to sprindown has got to be the worst thing ever. Powermatch it is.


#20

if its any consolation, power fluctuations doing intervals outside are far greater than your workout chart above.