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Wondering about some of the power readings here

Posted: Mon Jun 05, 2017 3:30 pm
by flahutewannabe
I'm still wrestling with the Power readings I'm getting and whether my profile is set up as well as can be. In general, I'm wondering if the power readings with head/sidewinds are too high, and those with quartering/tail winds too low.

My two most recent rides have been in pretty windy conditions, and in each I've had some power readings that have me scratching my head.

Also specifically on the 6/4 ride (yesterday) two longish (for our area) downhills showed big power very inconsistent with perceived effort (see around 7 with headwind and 10 1/2 miles with quartering tailwind). On both I was pedaling with some pressure on the pedals (not soft pedaling) but not at all maxing out what I was doing, yet both went 400-500 watts.

Thoughts? Profile tuning needed?

Re: Wondering about some of the power readings here

Posted: Mon Jun 05, 2017 5:56 pm
by Velocomp
It's very difficult to tell from your files if your PP is properly calibrated, but let's assume it is...

On the downhills if you did any aero tuck whatsoever, this would cause the high watts. You were descending in very strong headwinds, so this seems very possible.

On the tail wind portion of the ride you often had strong tail winds that were approximately the same as your bike speed. Under conditions of very low net opposing wind, PP can read low.

Re: Wondering about some of the power readings here

Posted: Mon Jun 05, 2017 6:48 pm
by flahutewannabe
Thanks, John. What would you want to see to confirm proper calibration?

FYI, I did not move off the hoods during the ride (maybe once or twice to the tops, but not the drops) so I was very conscious of not doing anything to change my aerodynamics during the ride. So an aero tuck is not a potential cause of the high power readings on the downhills. What else could be influencing the high power level?

Actually, I have been thinking of another question for you on that topic as I'm finding myself trying to lock into one position so as to not mess with the power readings (probably overthinking it and certainly not something to optimize while actually riding!) I work on framing that question in a separate post.

Re: Wondering about some of the power readings here

Posted: Mon Jun 05, 2017 7:03 pm
by Velocomp
Aero watts vary as the cube of the speed. So, on a down hill, where you're riding faster, ANY variation in position can result in higher watts.

Around mile 11.5, your total opposing wind speed was as much as 40 mph! I'd be hanging on for my life...