Cal Fine Tune

Cal Fine Tune

Postby DavidK16 » Wed Jul 12, 2017 4:30 pm


Would you mind taking a look at the attached file and letting me know if the calibration looks good? For the most part the Powerpod power data matches up well with my Powertap data but there are a few outliers and possible issues. I want to be sure the matching is a result of the calibration and not coincidence. Hopefully I’m at the point of fine tuning.

The parameters of the ride: TT bike on an outdoor concrete 380m east-west velodrome, wind from the ENE at 2-4mph, Zipp tubulars, 4x5 speed-based intervals, 4x1 VO2 intervals

My questions re the file:

• Does the wind profile look right or is it too asymmetrical given that I was going around a short loop and wind conditions did not change?
• Is the .0021 CRR Isaac wants to use for tubulars on concrete a result of your own testing or from a third party source? It seems very low – I actually used .0025 in the file. I know Analytic Cycling uses .002 as the CRR for tubulars on concrete but there seems some discussion about where he got that number. Absent Isaac or Analytic Cycling I’d likely have gone with something around .003.
• For 3 of the 4 speed-based intervals the PP and PT were within 5-7W of each other but for the third the PP was about over 20W lower. Can you see any obvious reason in the data for that?
• For all 4 VO2 intervals the PP was 20+W over the PT. Is there something about opposing force power meters that causes some kind of lag before they settle down and that would result in that difference?

Am I good with my calibration or would you suggest any modifications?

Any help would be appreciated.

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Re: Cal Fine Tune

Postby Velocomp » Wed Jul 12, 2017 6:01 pm

If you have the .tcx or .gpx file from your PT, we should be able to dial in things precisely.

Your basic ride file looks good...
John Hamann
Velocomp CEO
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Re: Cal Fine Tune

Postby DavidK » Wed Jul 12, 2017 6:59 pm

John, thx for the quick reply. TCX file attached. Let me know if you need anything else. DK.
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Re: Cal Fine Tune

Postby DavidK » Mon Jul 17, 2017 2:17 pm

Hi John, just hoping to get this back into your to-do list. Thx. DK.
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