Dumb trainer/Powertap C1 chainrings to Kickr


#1

Spent a couple years with the dumb trainer/C1 combo, switched to Kickr this year. FTP is 10% lower. Workouts and FTP setting seem just right with the Kickr (barely able to finish over/unders, pretty smashed after a 110 TSS workout.)

Just wondering if anyone else experienced this amount of decrease (or increase) in FTP when switching to/from a smart trainer to a powermeter for workouts.


#2

Are you using the power meter as your source of power or the trainer?


#3

using the trainer power. powermeter is on a different bike.


#4

In that case then it is likely just a discrepancy between the readings on the power meter and the readings on the trainer. You changed measurement devices - this is normal and nothing to be concerned with.

I would suggest putting the bike with the power meter onto the trainer and recording both the trainer data and the power meter data on a couple of rides so that you can understand the different readings between the two devices - this will let you translate your FTP while training to outdoor efforts (particularly helpful if you use power for pacing outdoors to know that 310 watts on the power meter is equivalent to 325 watts on the trainer)


#5

Ok, I was thinking of doing that. I was just wondering if the Kickr could be off by that much (10%) compared with other devices.


#6

Yup, absolutely possible


#7

Power measured at the hub should always be lower than power measured at the crankarm or pedals due to power lost through the drivetrain. Also, its also possible that your C1 is off. There will always be a bit of a margin of error with power meters.


#8

Good point, didn’t think of that. My pulley isn’t perfectly aligned with the cog I’ve selected on the trainer as evidence by the noise, nor have I oiled my chain since I’ve put the bike on the trainer about 25 rides ago, so boom, there’s my power discrepency. I don’t feel as discouraged now.