How far off is your smart trainer?

I’ve owned a few kickrs over the years as well as a few different power meters.

I’ve tested the power meters against others (pedals vs wheels vs cranks on the bike at the same time) and I’ve never had a significant difference between them - either inside or out

However, whenever I record the power numbers I get out of any of the three kickrs I’ve owned I consistently record higher power from the kickrs than I do from the power meters. My current setup I can record 350 watts from the pedals and the kickr tells me around 370 watts.

I link up a different garmin to the kickr and the power meter and record a solid five minute effort holding a set wattage to get the average and thus figure out the difference (note that the difference grows at higher power numbers )

I love my kickr, but it should be reading lower than the pedals (loss from the drive train), not higher. Has anyone else had a similar experience and done the testing necessary to confirm? Curious if it is unique to me and my various setups or if it is across the board with smart trainers

Above about 200w I find my flux is more or less bang on with my Power2Max but I haven’t done any rigorous testing to prove this. It’s close enough that I’m happy with it.

My Kickr (gen1) reads about 10-20w higher than my Quarq, depending on the wattage. I now use powermatch exclusively, for this reason.

Just did an FTP test and had my Elite Directo connected to trainer road and my Quarq connected to my Garmin. Compared the two after the test and the Elite Directo was about 20-30 watts higher.

I have a Tacx Flux and a FSA Powerbox (Power2Max). And the offset in power depends on gearing in ERG-mode. I always suspected this but made a small test yesterday while I was doing a workout. Both PM were calibrated prior to the last interval set with the data.

The gearing was set with the small chain ring in front and for each interval a changed to a smaller cog in the rear. Producing a higher flywheel speed for each following interval. I change the gear just prior to the 5 sec burst in power.

I cant see the speed (which represents the flywheel speed) in the analyzer in trainer road but it shows in garmin connect


Interval 1 (1 min 3rd largest cog)
Flux: 239
P2M: 229
Offset: -4 %

Interval 2 (2 min 4th largest cog)
Flux: 238
P2M: 230
Offset: -3 %

Interval 3 (2 min 5th largest cog)
Flux: 238
P2M: 235
Offset: -1 %

Interval 4 (2 min 6th largest cog)
Flux: 239
P2M: 241
Offset: +1 %

Interval 5 (1 min 7th largest cog)
Flux: 238
P2M: 246
Offset +3%

I guess this is a trainer specific problem and using power match would solve this if the problem lies in the Flux. However I don’t really like power match during intervals since there is a delay in power and during over/under intervals this just drains my legs before the power is matched.

I did a ramp test earlier this week recording the data from both the Flux and the P2M. During the test i didn’t change my gear. According to the Flux my max 1 min power was 361 W yielding a new FTP of 271. On the P2M my max 1 min power was 345 yielding a FTP of 259. Thats a 5% difference.

But as long as I don’t use powermatch and stay in roughly the same gear as when I was doing the test i guess it really doesn’t matter and I can use the FTP of 271 for training. Before testing my FTP before the outdoor season I will do a new test and record the data from the P2M and use this for outdoor training instead I think.

Anyone else experienced this with difference due to gearing in ERG-mode?

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