High power readings when riding with a tail wind

[pb21]

First 'proper' ride with my new PowerPod yesterday and was generally very impressed and happy I suspect the readings are slightly too high, maybe I need to adjust my CdA down a bit.

The only real issue I noted though was that on tailwind and/or downhill sections the power numbers would be MUCH higher than I would expect. On my ride yesterday I noted this a few times, most notably towards the end with the strongest tailwind (kms 102.5 to 104.5 on the attached ride file). The average for that section is 283 W with regular peaks above 400 W; I would estimate, based on my effort, these are both at least 100 W to high.

It is probably worth noting that the tail wind was relatively gusty, could that explain why?

Also I was wondering that when looking in the 'Analyze Route' option and then 'Show Tilt Plot' that the tilt difference increases when going downhill and is at its greatest at the end of the ride when I noticed the biggest differences noted above.

Thanks in advance.

[pb21]

I have just done another out and back calibration type ride. This involved a headwind into a slight uphill gradient on the way out and the opposite on the way back. On this ride, on the tailwind downhill return section the power numbers didn't read high and would be what i would expect, so maybe something was a bit weird yesterday!

Would you be able to check and recommend if I should change anything?

The current calibration numbers were based on a previous out and back ride I did on Friday, but this may be a better one to base it on...

Thanks

[Velocomp]

If you compare the profiles from your two rides you'll find that they are identical.

I think your PP is properly calibrated, so I'd just get out there and ride...

[pb21]

Thanks for your reply.

Yes you are right the profiles for the two rides are the same as I did today's ride without changing anything, i.e. the same profile as yesterdays ride.

I was looking at using the 'Check Calibration' tool on today's out and back ride which suggests the following changes:

Aero 0.456 -> 0.480
Wind Scaling 1.232 -> 1.296
CdA 0.370 -> 0.370 m^2
Fric 6.948 -> 6.948
Riding Tilt -0.4 -> -0.4 %
Crr 0.0043 -> 0.0043
Cal Weight 85 -> 85 kg
----------------------------------
Avg Power 155.4 -> 133.8 W
Avg Wind -1.2 -> -0.5 km/h

I think these may be better numbers to use as they give lower power numbers, which I suspect are more likely, and I would prefer to underestimate than overestimate!

[Velocomp]

No problem; but check your next ride as well. When you use the check calibration feature on a long ride it might not be as good as the check calibration feature on a short ride.