Velonews: Technical Faq: Testing Aero Helmets


Jan 3, 2005
Giro's new Synthe helmet provides many of the aero advantages of other helmets without the unsightly aesthetics. Photo: Caley Fretz |
Dear Lennard,
I’ve bought into Giro’s helmet technology in a big way. I own an Air Attack Shield and Synthe, so imagine my disappointment having read this “independent” test.
Have I been taken for a “marketing mug,” or are the test parameters so fuzzy that no one can lay claim to the definitive best/fastest helmet?
— Mick
Dear Mick,
I would pay attention to the comments at the bottom by Giro’s Rob Wesson. From having doing lots of wind tunnel tests myself, I know that “garbage in, garbage out” applies as much to aerodynamic testing as it does to computers. I’m by no means saying the test was garbage, but the fact is that:
— There are many different ways that riders hold their heads on the bike.
— People have different shapes of heads and ears and necks, with different sizes of helmets that may test differently relative to each other.
— There are many different wind angles, as well as speeds, that riders encounter.
This test seems to have only tested one head shape, one head position, and one wind angle (straight on). And the point Wesson makes about inconsistency of strap taping seems valid; when you’re talking about the small amount of total drag involved here, the presence or absence of a single flapping strap can be significant.
Still, CyclingNews should be commended for going beyond marketing hype and taking these helmets into the wind tunnel. I’m not sure a perfect test for aero helmets exists, but I’m certain that this is better than no test at all. It’s generally also true that the first stab one makes at testing something is not definitive. I’m sure they learned from this test and have plans for how to improve it.
I remember the first time I went to do some wind tunnel testing at Texas A&M in 1989, a new company named Camelbak was there. I saw them running tests with riders on aero bars in the tunnel with early water-filled Camelbak hydration packs on. It was visually obvious that the backpack was providing more drag than no backpack would. However, I later saw claims from Camelbak to the effect that wind tunnel testing at Texas A&M showed that their hydration packs were more aerodynamic than a water bottle! I dug deeper into this with the guys who performed the test, and it turns out, the comparison was made between wind tunnel results of a guy riding while sucking on the hose of his hydration pack and a guy riding while drinking out of a bottle! So you could not say that they were lying, because the results indeed showed that in this one instance, the rider with the pack was faster, but leaving out how it was done was misleading. It leaves out the fact that you always have the drag of the hydration pack when riding with it, but you only occasionally have the drag of holding up a water bottle to your mouth while riding with one of those!
I would not make the assumption that people who work on helmets all the time don’t know what they are talking about when they say their helmet is faster than others. On the other hand, I suspect there are lots of things we don’t know about how helmet brands test their aero lids in wind tunnels and that they may very well be reporting the one set of circumstances that favors their helmet and neglecting to report the results of other tests using different parameters in which their helmets fare poorly. The million-dollar question, and the one you are not likely to get answered by manufacturer claims of performance, is whether the favorable results for the product apply to you when you’re the one riding with it on.
― Lennard
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