My watts are dropping when I climb

Bugs and Support
1

When I climb, my watts on Zwift are much less than the watts on my PowerTap

My set up is a Wahoo Kickr Snap and I ride with a wireless PowerTap wheel, so every ride I’m seeing my power output from two different sources. Typically, they’re slightly different - 5 watts, sometimes as much as 10 (my FTP is 240) but mostly consistent, except when I climb. For some reason, the Zwift watts are a solid 25-30 lower. So while my PT says I’m putting out 210 watts, Zwift will say 180-185. So which is right? Well, it feels like the PT is right. I’ve put 4k miles on Zwift this year so it I think I have my perceived exertion dialed into my actual power output. I just did Tour stage 6 up the Alpe and struggled to generate 190 watts on the climb, which shouldn’t be too hard for me. Interestingly, this delta between the two readouts does not occur on flat or rolling courses. Before you ask, I calibrate my PT weekly and run a spindown on Zwift at about the same frequency. My back tire is kept at the proper psi and the firmware for my kickr is up to date. Anyone ever have this experience? Any thoughts as to why I’m getting it?

2

I would trust your PT over the Snap. I would pair the PT directly with Zwift as your power source instead of the Snap. Pair the Snap as the Controllable Trainer.

1 Like
3

Yeah I hear you. I trust the PT over kickr as well but unfortunately my PT is not ant + so I can’t connect. Anyway, the kickr wattage shouldn’t be dropping like this. I suspect it’s a wahoo issue and not a zwift one so I’m reaching out to those guys.

4

I have the same/similar issue (but on a Tacx Flux), mine starts off okay, but after a couple of gear changes the watts for the same exertion drop by 25-30. That’s even when I return to the flat.
It’s disconcerting, because it screws up any chance I have of improving my ftp score.

5

I have the same problem with my PowerTap SL. I zwift on a Tacx satori wheel on trainer. The watts are generally much lower than it should be especially on the climbs. I cant seem to do a calibration with the powertap on zwift. Is there a way, especially using a non smart trainer to check the powertap.