PowerTap G2 Hub and "Over-Easy" FTP Tests / Workouts

[megnotmegan541]

Hi all,
I recently put my Garmin Vector pedals on my “outdoor bike” and put my Powertap hub on my trainer bike. I use a Wahoo Kickr Snap, PowerTap Hub G2, and TrainerRoad. I currently have power matching set to ON (the new version of powermatch, not “legacy”).

My problem is this: I can’t for the life of me dial it in so my power feels accurate. Today I did an 8-minute FTP test, where I should be able to hold around 190 for each 8 minute interval. I would settle in at that power and very quickly my cadence would just get too high to maintain, so I’d stop for the wheel to slow down, then start up again. I even tried bumping up to 105%, then 110%, but without fail I’d out-spin the test. 190 felt like a breeze (which it really shouldn’t). Obviously, the results were very inaccurate since I kept having to stop pedaling!

That said, my workouts have felt way too easy as well.

Thoughts on the best way to remedy the situation?? I don’t want to have to go back to the garmin pedals, but I will if needed.

Thanks!
Meg

[mcneese.chad]

What device did you use to get your current FTP?

If it was the Garmin pedals and not the PT hub, you may need to retest with the hub and base your new training off that new value. As nice as it would be, there’s no guarantee that the two meters “match”, especially since they measure at opposite ends of the drivetrain.

What trainer are you using and are you in ERG mode?

[megnotmegan541]

I was using the Garmin pedals when I got my last FTP. I’ve been in ERG mode in all tests. Maybe that’s the issue??

Trainer is Kickr Snap (wheel on)

[mcneese.chad]

So the power meter change is a variable, and means you should be cautious about assuming they read the same. So a fresh test with the hub is appropriate since you plan to use it for now.

As to ERG, are you watching your power data and trying to hit the target by changing your input (cadence)? If so, stop watching power. In ERG mode, your main responsibility is to apply a steady cadence and let the app control trainer resistance to hit the target. Trying to fix a low power value by speeding up leads to a rev’d out cadence like you described.

[megnotmegan541]

Thanks Chad!
I didn’t have this issue with the Garmin pedals (the tension quickly adjusted when I increased or decreased cadence). In this case, there appears to be a significant lag.
I will try again by controlling my cadence and seeing if my Wahoo can keep up.
Thanks for your help!

[mcneese.chad]

It may well be down to the broadcast power meter data differences between the two meters, as well as the potential impact on the “look” of that data since they are at totally opposite ends of the power train. The pedals typically react and show power much quicker and sharper, while the hub will be more “damped” in comparison. All just speculation, but might be related to the differences you are experiencing.

Good luck figuring it out and I expect you can get used to the new setup once you get familiar with it’s quirks.