Power only accurate on flat and when climbing

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andrewschear
Posts: 7
Joined: Sun Apr 15, 2018 5:47 pm

Power only accurate on flat and when climbing

Post by andrewschear » Mon Apr 16, 2018 12:26 pm

Jon,

It seems that my Powerpod matches my power on my smart trainer on a flat or climbing effort. When descending at all, the power is really high. The more the descent, the more it's off. In order to get the numbers good, I had to use a CdA setup for "drop bars" even though I'm on a tri bike. I suspect it's because my fit is not extremely aero. (aero pads about 1cm below seat). When set to tt, the numbers are 10-15% low (according to my same HR per watt on the smart trainer).

Attached is my calibration ride and a ride with some hill work. I'm not going to coast on a 1% descent, as that would put me at a huge disadvantage.

Also, the amount that Isaac said I climbed vs. my garmin is quite different, garmin said about 2,000 which coincides with google, and Isaac said about 1300.

Thoughts?
Attachments
iBike_04_01_2018_0649_2_Miles_CalRide.ibr
(93.69 KiB) Downloaded 8 times
iBike_04_15_2018_0639_0_Miles_HiDef.ibr
(1.6 MiB) Downloaded 8 times

Velocomp
Velocomp CEO
Posts: 5430
Joined: Fri Jan 11, 2008 9:43 am

Re: Power only accurate on flat and when climbing

Post by Velocomp » Mon Apr 16, 2018 1:33 pm

When I opened your ride file and saw the large downhill watts, before reading your post carefully I thought to myself "I bet he's on a TT bike". Turns out, that was a correct guess!

You weigh about 158, and I infer your height is about 5' 9". That would imply a CdA of about 0.25.

I adjusted your ride file for this CdA, and your downhill watts diminish significantly to normal values.

I don't have an explanation for the elevation gain difference.
Attachments
Andrew_04_15_2018_0639_0_Miles_HiDef.ibr
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John Hamann

andrewschear
Posts: 7
Joined: Sun Apr 15, 2018 5:47 pm

Re: Power only accurate on flat and when climbing

Post by andrewschear » Mon Apr 16, 2018 1:35 pm

John,

Thanks, I'm 5'6", not sure if that'll make a difference.

I'll plug in the new value.

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