Understanding wheel speed and wind speed

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Bugsbunny
Posts: 31
Joined: Wed Apr 27, 2016 12:00 am

Understanding wheel speed and wind speed

Post by Bugsbunny »

Hi John

In ISAAC, how do we interpret the graph for wheel speed (in white) and wind speed (in blue).

If the blue curve is ABOVE the white curve what does that mean?

And conversely if the blue curve is BELOW the white curve what does that mean?

A recent ride (with NO drafting) I notice a big section of blue under the white curve when I'm climbing. How do I interpret that to mean?

Thanks for your help as always

Bugs
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Velocomp
Velocomp CEO
Posts: 7793
Joined: Fri Jan 11, 2008 8:43 am

Re: Understanding wheel speed and wind speed

Post by Velocomp »

Nothing is wrong.

When you're climbing a steep hill, your slow bike speed means that wind speed is low, too (particularly if there is a tail wind). It is difficult to measure accurate wind speeds when wind speed is low, but this makes no difference, because wind speed has a negligible effect on watts at low speeds. On uphills, blue wind speed is substantially less than white bike speed.

On the downhills, you have a slight head wind, so wind speed is above bike speed.
John Hamann
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