Two Wheel Blogs

There was a time in my life, say before about 5 years ago, when I didn't do much, activity wise. I weighed about 45 pounds more than I do now. Even worse, I'd watch golf on TV on the weekends.

Wasted youth, I know.

The aero testing Andy and I have been doing these last few weeks has dredged an expression up from the depths of those wasted weekends watching golf: "The wind is but a zephyr." I don't remember his name, and his British accent was rumored fake, but that was one of the pat expressions he'd use to fill the dead air as we'd watch some guy toss grass to get a read on the wind.

When you do this kind of testing only calm conditions will do. You don't even want any zephyrs, whatever they are. That's the rule: Wind speed is hard to account for, so choose days when you can eliminate it as a variable in your aerodynamic drag computations. Evaluating timetrial positions is much easier this way.

But today Andy posted a note on the wattage list, half-jokingly pointing out that you could use your bicycle powermeter as a wind speed indicator. As usual, he's right. If you do the math, you can back a pretty good estimate of wind speed out of timetrial position and aerodynamic drag test data.

The chart below is a chart of wind speeds during my aero test runs over the last three weeks. The wind speeds charted nearly imperceptible. It's very hard to detect air moving this slowly, but it has a measurable impact on aero test results.

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