My Kickr Snap consistently reads about 20 to 25 watts lower than my Stages. I am wondering if part of this difference is the drive train efficiency. I just listened to a podcast on this topic from VeloNews (https://player.fm/series/velonews-podcasts/tech-pod-how-to-reduce-your-bikes-friction-on-a-budget) and they were saying that driving efficiency is typically 90 to 95% if my memory is correct. So, it’s possible that both power readings are accurate and the difference is due to losses in the drive train.
Interesting. And makes sense intuitively, but for me it was the opposite. The Snap always read higher, particularly near Threshold. Adding the Stages was humbling as I had to lower my FTP by 30w.
I use a 2017 Kickr Snap and I have a Quarq XX1 PM ordered, so I’ll be doing my own comparisons shortly. My assumption is that power measured at the crank spider (Quarq) has to better/higher than at the roller of the Snap.
Regarding Stages and other PM versus Snap power, here are my thoughts;
It could be that the Snap and PM have different power curves that intersect at some point. Comparing them on a graph would be interesting. For instance and using nice round numbers, at 100 watts the Snap could read high compared to PM, as the drivetrain may have less affect on power. Then say at 200 watts both the Snap and PM’s curve could “intersect” and the power could be accurate for both. Then moving up the wattage, say 300 watts, the Snap could read low since the drivetrain loss could be more significant or read high because it’s “curve” is different compared to your PM.
Considering both the accuracy of each device (Snap and PM) which is usually 1.5-2.0%, it could be as the watts increase those watt gaps become greater and greater. A 5% difference at 100 watts is not noticeable, but at threshold you’re likely to notice that.
Comparisons of Snap versus PM could change over time expecially when you consider the drivetrain and wheel on. The drivetrain will surely get dirty, loose it’s lubrication and have more friction. Also, if you’re not regularly checking tire pressure, cleaning the wheel and roller and performing spindown calibrations, the numbers are sure to be skewed. Also if you have temperature fluctuations (trainer in garage/basement) it’s sure to have at least some percentage of affect.
I think with any wheel on trainer you just introduce many more variables than a direct drive and even more so than a crank based PM. However, I think it at least gives you to your specific trainer consistent results, which is all that really matters. It’s just not comparable to other measures of power.
Just wanted to verify that enable Control w/ANT+ Power Meter in Wahoo app and pairing your Kickr to TR with Bluetooth will NOT use the trainer power and use your Ant+ power meter? I tried this earlier but i wasn’t getting cadence information from my ant+ power meter. I’ve been having a TON of issues with TR power match and would like to try a different method as a test.
As for cadence data, you’ll need to pair your PM and set it to “cadence only.”
How do I know if the Kickr is using my Pioneer PM? If I use the Wahoo app, and set it to use Ant+ for power I can see it if I select a workout from the Wahoo app. I have to either Delete the Sensor or turn Bluetooth off on my phone for the Kickr to pair to Trainer Road. There isn’t a way to confirm that I’m actually using Pioneer power
- If you have the trainer and power meter paired to the TR app, it is using PowerMatch by default.
- You should be able to check in the devices. See the following for full details:
When I was using “Control w/ANT+” the only way to get it working with TR app was to:
- Start Wahoo Fitness app
- Start workout in Wahoo Fitness
- Verify it connects, because 1 out of 10 times it didn’t
- Force quit Wahoo app
- Start TR app
That appeared to work, although I’m not convinced it worked 100% based on some other testing. Calling Wahoo support they will tell you it only works with Wahoo Fitness app.
Finally I gave up, disabled “Control w/ANT+” in Wahoo Fitness app, and started using TR PowerMatch. A recent TR app update has improved the PowerMatch with the Kickr at least with my 2017 wheel-off direct drive model.
Actually I’ve been having a ton of issues with TrainerRoad and I’ve been working with support for a month now. Tons and tons of issues. I wanted to try pairing the PM with power match on the Kickr then pair the Kickr with laptop/TR using only Bluetooth. Someone told me on this post it’s possible but I also have to pair PM to TR for cadence.
Oh, well that sucks. I’ve been trying this for a few days now.
I can’t wait until time change…I’m just going to use the TR workouts as a template and just do the dang things outside. All my gear sucks. I’ve tried so much crap I don’t even know what to do next
Give what I wrote a shot, might work just fine in the interim.
Or you could buy a ANT+ adapter for the laptop, and go all ANT+.
Or forget cadence and do what TR support suggests.
That’s interesting. I enabled Control w/ ANT+ one time in the iOS app and it has worked ever since. I know this because I run my Garmin on every ride to make sure my power is tracking correctly—my Snap is generally 10-20 watts off compared to my PM, but it’s been spot on every since I started using Control w/ ANT+.
That’s the only way I know of to make sure it’s working: just doing a fair bit of comparison first between your trainer and PM, then continue to monitor after the Control feature is enabled. If TR and your head unit are displaying the same power numbers, then you know Control is doing what it’s supposed to.
That was how I originally tried it, and a few rides later the Kickr 2017 failed to connect to Stages power meter. I played around with it for weeks, it generally worked but not always. Got lazy early on and stopped using Garmin. Then I used Garmin and wasn’t seeing the same power between Kickr and Stages. That’s when I gave up.
Had been using the Wahoo app trick for two reasons: 1) Erg mode speed simulation to get the Kickr to report power based speeds (instead of ridiculous flywheel based speed), and 2) verify Kickr connected to Stages before starting TR app.