Tuesday, April 22, 2008

Aero testing #3 - results

[quote=fishboy,Apr 24 2008, 01:02 PM]Test number three this morning. Limar Chrono 05 v Giro Advantage 2 with taped vents. Subjectively, don't think taping has helped improve the situation, but need to run the data.
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Better get to the LHS (local hardware shop) and get some duct tape.

Turns out that with the vents taped the Giro Advantage 2 performs exactly the same as the Limar. Kind of surprised me - how can 5 pissy little vents on the front of the helmet result in 0.9-1.0 kmh slower speed at 200 watts??? :blink: Should repeat this test with vents taped and de-taped to make sure.

So the first rule of aero helmets would seem to be: [quote]Buy aero helmets without vents in preference to ones with vents.*[/quote]
And the second is: [quote]If you have vents on an aero helmet, tape them.[/quote]

* Sure, if you think you're going to have a hot head, get one with vents, and ride that bit slower.

Here's the data:

[img]http://www.efirst.com.au/rob/fishboy/TapedGirovLimar.gif[/img]

Also interesting to note that this test with done with different clothing to last time - looser (but warmer) jacket which is not skin tight. This jacket is responsible for dropping the speed at 200 watts from:

37.1 and 38.1 kmh for Advantage 2 and Chrono (test 1)
37.1 and 37.9 kmh for Advantage 2 and Chrono (test 2 - same clothes as test 1, skin tight)

to

36.0 kmh for both helmets (test 3) - looser jacket, non skin tight

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