Aerodynamics - Helmet vs. Casquette

I have been able to turn up all sorts of studies on various helmets and their relative aero efficiency, but I am totally striking out on any data between helmet and no helmet/casquette.

Anyone have any sources?

Gets popcorn…


OK, preemptive statement here:

  • Let’s keep this on the topic of aerodynamics.
  • I’d rather not have to prune this thread as the result of an ‘us vs them’ approach.
  • Most of all I do not want people telling others what they should or should not do. (already happened)
  • Personal opinions and choices can and will vary. No one is right or wrong.

Back to the discussion at hand, aerodynamic comparison.

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Thanks Chad.

This is really my only question, academic curiosity and all.

The human head is not shaped for aerodynamics and cannot be easily manipulated to be aerodynamic.

An aero helmet is made out of moldable material that was manipulated to have better aerodynamics.

At par value, an aero helmet will be faster in 99.9% of cases, except in a rare freak case where someones head is an aero genetic anomaly.

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One tiny bit of info found via Google:

  • Aero vs. No Helmet
    • If you wear an aero helmet, you will have less drag than if you’re not wearing any helmet. That’s because even if you have short hair, it creates drag. The aero helmet lowers drag by 100 g at 30 mph when compared to riding without a helmet, according to "High Tech Cycling” by Ed Burke.
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Interesting. So it looks like hair in the breeze is in between an aero and non aero helmet in terms of drag.

Data coming from giro at the launch of the vanquish helmet


:thinking: does that mean I have to shave my legs and head?

Your riding position would make a huge difference because of the inefficient shape of your head. In a helmetless TT you could probably turtle so much that your head sees little wind. But in a road race you have your head up and the wind is hitting your cylindrical/spherical head straight on

I remember when Chris Boardman was in negotiations with the UCI about the then new athletes record, there was a massive dispute about what kind of helmet he had to wear since not wearing one was much faster than the non-aero helmets they wanted him to use. It was touch and go whether he was going to try it unless he could use something that had the vents covered over. In the end he only beat Merckx’s record by 10 metres!


Perfect, this was exactly what I was looking for!

So a few handfuls of seconds between aero road and TT helmets over 180km at 250W.

Wish I hadn’t bothered reading reviews and choosing one.

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Honestly, I run a mildly aero helmet, Oakley, and I just got it for fit and looks.

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The data coming from Giro is based over a wide angle of yaw, actually a bit too wide compared to what you will see in real life. That is why the air attack is so good in that table, at high yaw it is a better helmet then a long tail helmet.

At the track for a aero brick on the TT bike (cda>0,3) the girl vanquish gave 20 watts improvement over a Giro foray, a LG P09 gave another 2 to 8 watts increase over the giro vanquish. At 45km/hr

For me the giro vanquish and LGP09 gave about the same result so I hae to do some ABAB testing on them.

Any idea how a long tailed helmet compares to a standard road helmet? Got a Giro A2 for my a-race so looking forward to seeing those gains