SpongeDad

It seems like when folks get to a wind tunnel, aero helmet selection is very individual.

I was just wondering if there were any good studies suggesting that one helmet is demonstrably better than another? Or whether adding dimples does anything other than make you look like a golf ball?

thx

Grumpy McTrumpy

Uvex FP2


Dr WJO did some helmet testing in the tunnel. Not sure on other tests out there.

Hida Yanra

IIRC, dimples are rather worse,
everything else varies based on your position, how well you can hold said position, and what races you are targeting with the helmet.
(for example, I'd take a very different helmet to the 10mile Frozen Flatlands TT in March than I'd take to Ironman Kona)

king-tony

It depends on your position on the bike. The UVEX is awful for me, the Giro Advantage II works well, but was only marginally better than the LG. If you are unsure I would generally error on the side of a helmet with a shorter tail. If you do not have good head discipline on the bike it will hurt you less than a long-tailed helmet.

El Diablo Rojo

This. Doing TT position testing with Racer Ex last weekend we used three different helmets and a variety of positions (Univex/Giro Advantage2 and the new Rudy) and we found that in my current position the Giro Advantage 2 was faster by nearly 1km/ph while the reverse was true in the hands up Flandis style the Univex was the fastest (and this set was the fastest of all). Rudy was the slowest in all the runs, but again it really has everything to do with your position and body type.

SpongeDad

That's a huge difference, especially over another TT helmet.

El Diablo Rojo

Yeah we got some really good data..did soooo many runs, 4 runs per helmet/per position. As long as I can adapt and make power in the Flandis/Univex position I should see a gain of around 10w or more.

Dalai

Definitely a personal thing.

From my tunnel session - I was restricted to a smaller number of helmets due to only a few having Australian compliance (we have a separate standard down under) and tested the Limar Speed Demon vs the Limar Crono 5 and the CE approved Bell Meteor II.

I initially bought the Limar Speed Demon as it 'looks' faster with the longer tail. I also have an 07 Bell Meteor which I had used in Triathlons (rules allow non AS tested helmets) and initially tested both in the tunnel to see if there were any differences in the two helmets (The CE certified helmet can still be used on the track too) and then it was suggested I try the Limar Crono 5.

Although shorter, the Chrono 5 with minimal venting (none on the front section) offered me a noticeable wattage saving of 10 watts over the longer tailed, vented and sculptured Speed Demon. The Chrono 5 also compared favourably even against the Bell which with it's long tail that sits nicely against my back. As you can guess, I immediately sold the Speed Demon and bought the Chrono 5!

As for the Giro Advantage II. Another rider in the tunnel that day had previously field tested this helmet against the Limar Crono 5 and also found a similar discrepancy between the two which was confirmed in the tunnel.

If you have a PM, a quiet loop or velodrome in calm conditions plus a friend you can borrow these helmets from I'd suggest some field tests to see what works best for you if you can't get to a tunnel.

In the mean time - One study - details posted previously on BTR...

Racer Ex 

Field test them at minimum, tunnel test them if at all possible.

Position factors in hugely. As does fit, I've had to grind out liner on two helmets to get them to sit well on my big dome.

Visuals can be very misleading; some helmets that look horrible actually perform quite well on some people, I've seen the old Rudy Syton be the fastest on certain folks.

Dalai

Totally agree. The generalizations I do see mostly hold though is the smoother / minimal or non vented helmet should be faster. Plus overall bulk makes a difference. Get the smallest size you can get on your head. * Looking at the overall frontal area the helmet has. Some have a one size fits all approach, others just seem bulky. The bigger the frontal area plus vents and design lines the worse I expect it to be.

*Within reason of course...

rruff

I'll probably be modifying all my helmets from now on. I got a Limar Chrono (universal size) last year and melted the styrofoam (propane stove and old spoon) to get it to fit right... also removed the plastic adjuster which was just in the way. Now I can tilt it back so the tail doesn't stick up and it fits great... and is fairly small compared to the alternatives. I tried a LG Rocket and Giro Advantage but in size L they are just huge... plus the LG had a gap at the sides. In M these were two were way too small but if I'd tried melting them they probably would have worked.