I have gotten myself a new Powermeter (Garmin Vector 3S single sided pedal Powermeter) for my bike while I previously only used my KickrCore for Training indoors. As far as I understood, as I want to use the same Power Numbers for Training In- and Outdoors, I will connect both during my indoor training rides and use Powermatch.
Now the Question: I expect my Kickr to read the Power slightly lower than the Vector 3 due to drivetrain losses. When I now start the workout (I hope I understand this correctly), the Workout might be a little easier using Powermatch because the trainer difficulty is dropped to the target watts measured at the pedals.
I know it is best practice to do a new FTP-Test with a new Powermeter or Trainer, but I just did one a couple days ago, and would prefer to wait a couple weeks to the next one as it kinda interrupts my training.
So my Idea until that would be the following: to do a ride and record both the Vector 3’s power and the Kickr Power. And then if the Kickr reads for example 10 Watts lower on average, I would raise my FTP by that amount until I can do a proper FTP-Test in a couple weeks. Would this work? Do you have any other Ideas or Input for this situation?
Any Help is much appreciated!
You’re logic is sound. Might even be close enough to where the minor difference wouldn’t have much affect in the workout execution abyway
Unless you see a wild difference @Speedy I think that’ll be fine with AT and AI FTP detection it should sort itself out anyway.
As Ryan and HLab have said, your idea is sound, measure the difference and go from there.
I would just add, check the difference at a few different wattages, and if you can work up the motivation either do a test, or at least a workout that you could use as a proxy for a test (used to be Lamarck, just something with decent TiZ at 100% threshold).
I say that because when I first changed from Virtual Power to Power measurement I stuck with the old FTP way too long because it seemed “close enough” and it absolutely kicked my butt. That should be the opposite problem for you (my FTP was high) and with AT you might be ok. I just wanted to chime in with a cautionary note is all. If it doesn’t feel right, don’t feel too attached to the number as you’ve got those pedals now for the long haul.
Unless you just rode your bike through a pig farm, let all the mud dry and then mounted it on the trainer…the loss from pedal power to power at the hub is going to be super marginal. On the order of a few watts.
Chains and pulleys are super efficient at transferring power. That’s why they’re used on bicycles.
I have a right sided power meter on one bike, left sided on others, use a kickr core inside without powermatch. I’ve never noticed a difference in RPE between them. Trainerroad has a unique ability to make every workout hard.
Thanks for all the great answers and valuable input! Much appreciated
Drivetrain losses are in the order of 4%. Not massive but fairly significant. It would be around 10W on a 250W FTP.
But worth noting that GPLama recently suggested on another thread that Wahoo factor in drivetrain losses in their power calculation for the Kickr. I tried to confirm this with Wahoo support, but they didn’t have a clue.
Regardless a back-to-back comparison will show any differences.
I wonder if that Wahoo feature is just the newest Kickr? I have a Kickr core and found it to read 4-5% lower than both my left side 4iiii powermeters and Power2Max unit on my last bike. That seems reasonable to me factoring in drivetrain losses.
No idea. It was GPLama who suggested it based on what he had been told. I did ask Wahoo support to confirm if this was true, but they didn’t seem to know. Your experience seems to suggest there is no compensation for drivetrain losses - at least on your Kickr Core.