Can you solve this CdA mystery?

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Velocomp
Velocomp CEO
Posts: 6784
Joined: Fri Jan 11, 2008 8:43 am

Can you solve this CdA mystery?

Post by Velocomp »

Yesterday I made a very simple adjustment to my bike. When I did my ride afterwards, AP told me that my CdA went UP by 25%! Not good...

Today I started my ride and was again getting the same, troublesome high CdA reading.

I stopped at the 2.5 mile mark, undid the adjustment, and my CdA immediately returned to normal. You will see the HR/CdA level drop right after the stop at mile 2.5.

What is the adjustment I made that caused/fixed the problem?
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John Hamann

Jesper
Posts: 3
Joined: Wed Nov 21, 2018 4:06 pm

Re: Can you solve this CdA mystery?

Post by Jesper »

Maybe, you tilted the handlebar...

Velocomp
Velocomp CEO
Posts: 6784
Joined: Fri Jan 11, 2008 8:43 am

Re: Can you solve this CdA mystery?

Post by Velocomp »

We ran our "mystery" question on Facebook, too. It was a pretty popular post!

The answer is: I had made an adjustment to my rear brakes, causing them to rub slightly against the rear wheel. The extra friction of the rear brakes caused me to pedal a bit harder, which caused my DFPM watts to go up (for the same bike speed).

Since AeroPod did not "know" that my brakes were causing higher rolling resistance, it calculated instead that the higher DFPM watts were caused by increased wind resistance--as expressed by a higher CdA!

As soon as I readjusted the bike, so that there was no longer any brake rubbing, things went back to normal.
John Hamann

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