Wind Tunnel Aero helmet test - Thoughts?

[TheKaiser]

I wasn't sure if I should post this in Road or Cycle Chat so mods please feel free to correct it if I was wrong.

Anyway, new aero helmet test on BikeRadar, with surprising (to me) results: http://www.bikeradar.com/road/gear/arti ... ted-44719/

Things that struck me were that the "eyeball" aero assessment doesn't seem very accurate in this case, as what appear to be very similar models with similar vent placements and shapes scored wildly differently (wildly being a relative term as the spread from best to worst only ranged about 2.5% of total grams of drag of whatever they were measuring), and some super smooth models were beaten out by comparatively well vented ones. I mean, I never would have guessed that a Bell Star Pro was more aero than a POC Octal Aero, and I certainly wouldn't have guessed that a Giro Air Attack would be the least aero helmet on test, falling below even the non-aero Specialized Prevail (which served as kind of a "control" model but ended up beating 3 of the aero models!).

They do point out that testing at different head angles can change results, but given that they ran the test at a tunnel that does helmet testing (ironically, for Giro, given that their models were the bottom of the heap) and James Huang seems like a pretty technically savvy guy, I have to think that this was a decent test protocol.

One thing that gave me pause was that the tape holding the straps down to the headform. First of all, that isn't reflective of the real world, as no one I know tapes their straps to their cheeks, but more importantly, they are taped down significantly differently from model to model. I'm not saying it was enough to ruin the results, and one would hope that the tunnel guys have done enough of this to be able to state exactly what the effect of the tape is, but I'm just sayin'...

[cajer]

All I'm going to say is that they are testing a helmet on a dummy without shoulders.

[kgt]

"Each of these helmets is billed as generating less drag than non-aero helmets but that wasn’t the case for the Giant Rivet, Giro Synthe, and Giro Air Attack (although keep in mind that could've changed with a different test protocol). All three were actually slightly slower than our benchmark non-aero helmet."

"The Specialized S-Works Prevail actually beat three of our aero road helmets in the wind tunnel."

And a helmet is supposed to be something easy to test...

[weenie]

the tunnel also didnt seem to be very modern.
that said i dont doubt the helmet doesnt make a significant enough difference between all these models. they're all pretty aero even the "non aero" ones. the only thing that really changed is how much marketing was put behind them and the attempt to create that impression - since its very hard for us to verify the results, makes it easy to market.

[cyclenutnz]

It's really not worth paying attention to numbers from the FASTER tunnel. That is the biggest testing error

[davidalone]

Jim Manson from ERO sports is on slowtwtich slamming the test.

[prebsy]

yeah I don't think testing at 20mph is fast enough and they stated that the rankings changed at 30mph. I guess the bonti won at 30mph and well at $175 it wins as well.

[spdntrxi]

All I'm going to say is that they are testing a helmet on a dummy without shoulders.

because they are testing helmets not shoulders.

[hasbeen]

Giro with a measured response pointing out plenty of issues with the test. Posted at the bottom of the test.

[0psi]

All I'm going to say is that they are testing a helmet on a dummy without shoulders.

because they are testing helmets not shoulders.

The way a helmet interacts with a riders shoulders can have a big effect on how a helmet tests.

Having said that I think the testing was reasonable with the exception of the tape used to hold the straps down. A dummy with shoulders would have made for a better test but the taping of the straps wasn't particularly consistent which would probably have a bigger bearing on the result. I'd take those results with a gain of salt.

[Rush]

All I'm going to say is that they are testing a helmet on a dummy without shoulders.

because they are testing helmets not shoulders.

The way a helmet interacts with a riders shoulders can have a big effect on how a helmet tests.

I used to be a professional aerodynamicist. I cannot emphasise enough the importance of this comment. You have to test the helmet on a cyclist in a riding position, other wise your results are meaningless because the pressure field around the cyclist (as opposed to just a dummy's head) are completely different.

Ex colleagues of mine have been involved testing AIS athletes in wind tunnels and they say exactly the same thing. Individual helmet performace will vary from rider to rider.

[Zigmeister]

If you guys read the comments from Giro and another manuf. at the bottom of the article, they make all of these points regarding first, the size of the helmet being too small for the dummy head. Not angling the head ever, a bald cyclist/no hair on the dummy used etc.

They bring up a bunch of points about why the test isn't that valid, and the standard variable is about 10gms anyway for various things. So most of the helmets are really considered the same aerodynamically.

On the other hand, manufacturers will all claim aero benefits and often using flawed methods, or too many variables to prove they are really much more aero at all, wheels/frames etc...80% of drag the the body/person on the bike. So how much would one of these helmets actually reduce the total wattage required while pedaling at a given speed with a human on board the same bike? Like 1W?

[Dalai]

So how much would one of these helmets actually reduce the total wattage required while pedaling at a given speed with a human on board the same bike? Like 1W?

I had a 10 Watt difference between aero helmets when tested in the Monash windtunnel...

[topflightpro]

When the guy running the wind tunnel provides a disclaimer about the true value of the results, you know the test is crap.

[Grill]

Even if you were to disregard the protocol, those results don't mean a thigh. I aero test more than most (3 sessions in the past 6 months) and I can safely say that individual position skews results massively. Meaning it's likely that they are all the fastest helmet as long as the appropriate person is wearing them.