Power Meter versus Turbo Trainer

Hi All,

I’ve been using a KICKR Core since joining TR last year and it’s been great. In the last few days I got a 4iiii (left side only) power meter because I wanted to have power for all my rides (inside and out).

Since putting the power meter on the bike (using power match with the 4iiii and KICKR) I’ve really struggled with the sessions I’ve done. I did an experiment this morning using only the KICKR on a workout while also using the 4iiii connected to my Garmin head unit. Comparing the power files from both, I can see that the 4iiii is consistently reading 12-20W lower than the KICKR. Have people seen such large discrepancies between their power meters and turbos? I guess if I just do a new ramp test using the 4iiii it won’t matter (provided the 4iiii readings are consistent overtime). But my (relative) FTP will drop by 15-20W… :sob: :disappointed_relieved: :cry:

Interested to hear others experiences.

Yep, pretty common, I’d trust the data from the power meter, it bruises the ego a bit, and you won’t be as fast in Zwift races but at least you’ll have a better baseline of your actual power.


I’ve got PowerTap P1 pedals and just yesterday realised what a difference single sided can make.

I was recording on my EDGE 830 and TR Android App; because the TR app only takes left side and doubles it the power shown on the two devices was about 6-7% off (my EDGE 830 showed a 53/47 L/R balance post session).

In my case, because my left leg is higher, it meant TR thought I was working harder than I was but if you are right leg dominant by 3% or more I could see it making your workouts difficult.

@Bryce for those of us with balance issues and dual sides PMs, is there any way for us to get “total power” into the TR App?

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Yep, I have the same issue. Was using the power from my Neo happily and then heard them mention on the podcast that the power reading from a powermeter is preferred. Switched to my left-only Stages and oh boy… Readings are much lower, thusly workouts harder. My right leg is probably stronger. I’ll use the Neo for the remainder of my plan, and switch to the PM for the next Ramp Test.
If I had a dualsided PM I guess the problem wouldn’t be so big (or if my power distribution was more even).

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I have a dual sided PM and just looked at my last 30 rides. It appears inside on my Kickr Core (using Powermatch) I tend to favor my right side 49/51 on average. However outside I favor my left 51/49 on average. There are some outliers, usually on trails where I have greatly favored my left, I believe when I get really tired. Most notably an MTB :100: where I was 55/45.

What does it all mean🤷🏽‍♂️.

I did some previous analysis of my new PM and my Kickr Snap found here:

Yeah, this is super common. You could put four power meters on your bike and end up with four (sometimes wildly) different results. Any time you change power sources, you need to do a new FTP test because of that.

As an aside, since you’re a Kickr user, I’ll also mention that I’ve had better results telling my Kickr to use my PM’s power instead of its own internal PM. Fire up the app, select your trainer, then scroll down and enable the “Control w/ ANT+ Power Meter” option and enter your PM’s device ID. From there you can disable power match in Trainer Road by setting your PM to “cadence only.” I personally found that to provide a smoother, more accurate experience with both my Kickr Snap and my Kickr Core.


That’s interesting, I’ll definitely give that a try. Since using power match these past few rides I’ve found it trickier to hold a smooth cadence because the KICKR is constantly adjusting resistance up/down on a slight delay. I end up with a very spiky power curve. Maybe I just need to improve my pedalling mechanics…

Nah, that’s also common because you’re not getting that artificial power smoothing. Ultimately, you’re getting the same workout regardless of whether the line is perfectly smooth or choppy. Don’t sweat that.

With the method I outlined above, you’ll get that artificial smoothness again, but if you don’t like it, you can disable “Erg Power Smoothing” in the Wahoo app for a more realistic look. I personally just run my Garmin alongside TR so I can glance at my “actual power” every once in a while.

Powermatch is getting a refresh in the near future. Make sure to sign up for Beta testing in your TR account to try it as soon as it comes out.

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I’ve had more consistent trainer vs. power meter results after warming both up for 10 minutes and then calibrating.

i now question my trainer power for the last two years because I never warmed it up before calibrating.

Fair point, I’ve noticed huge temperature differences in my KICKR before and after use. Before use it’ll be at room temp (usually around 20ºC) and after a session it often above 40ºC. That has to make a difference…

Most power meters have temperature compensation, and I’d imagine the Kickr is no different.

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i had a different experience. My Tacx Neo2 had lower power readings over my Stages LR and i posted a similar question before (but with a different power meter):

As we’ve seen the reports about shimano cranks and funky power readings from @GPLama , i opted to just use the neo2 power on my trainer rides.

You can’t assume this stuff if you want the most accurate readings. I’ve only had indoor power for the last three years. I just got a Stages. On first outing to do a 20 minute FTP I struggled and power was way down.

I late found that calibrating after 10 minutes of riding makes a large difference. Stages says in their manual that there is temperature compensation and they also say to calibrate every use for best performance. From my experience the later is required. It could be that the temperature differential between inside and outside is too great for the compensation.

Bottom line, if you are trying to compare do everything right, warm them up, calibrate and then see how far off they are.

Yeah, you have to calibrate a Stages on every ride. But when you calibrate shouldn’t matter that much. I’ve been riding a Stages for years and can’t say that when I calibrate it has made a big difference.

Tried that and my Kickr 2017 wheel-off didn’t always using the ANT+ power meter. Did maybe 30 rides and compared to Garmin recording. Gave it a chance and couldn’t trust it. One reason I went back to PowerMatch.

“smoother, more artificial experience” is what I found. Smoother? Yes. Have never finished an outdoor training session or hard group ride and said “if only the power was smoother” :wink: Power fluctuates when riding outside. Train more like you ride outside, don’t train to make prettier graphs. Your FTP is an estimate, zones are estimates with fuzzy endpoints, and your body isn’t a robot. Something to think about :thinking: :biking_man: :slightly_smiling_face:

I mean smoother transitions. Not a smoother graph. I even addressed the artificial smoothing in my next reply.

hey not picking on you, in the real world what is the value of a smoother transition?

in any case, my experience has been that any transition (e.g. smoothly bridging a gap) is more neuromuscular and teaching the brain and body to work together. Both on the trainer and outside.

completely agree on turning off Erg Power Smoothing - don’t let your trainer lie to you.

I mean, I don’t want to wait 30 seconds for my 2-minute interval to hit the specific power? That’s really all I’m saying, man. You’re reading way too far into it.

I’m seeing about 3 seconds with TR PowerMatch and Kickr wheel-off, have only seen 30 seconds when something is really wrong.

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