For less than $300, a full-on TT helmet can shave upward of five minutes off an Ironman bike leg.

When it comes to aero upgrades, nothing offers more bang for your buck than an aero helmet. Unfortunately, it’s not as simple as putting on an aero helmet and watching your bike splits plummet. Even the best helmet is only as good as the position of the athlete wearing it.

Head Position

“The head sticking up above the back is the biggest mistake I see among age-group triathletes,” says Ingmar Jungnickel, aerodynamics R&D lead at Specialized. “You want your head to hang in front of your body—not above it. If you look at world-class time trialists, you see their heads low, in front of their bodies. The top of the helmet is at the same level as the highest point of the back. That creates a huge reduction in drag.”

In order to teach proper position, Jungnickel tells athletes to pretend there’s a suction cup pulling their chin forward, but there’s a small weight attached to it, causing the neck to drop. Don’t worry about occasionally looking down and pointing the helmet’s tail into the wind, he says. “Any good aero helmet with a short or medium tail isn’t too sensitive to being exposed to the wind.”

Curves, Tails, and Visors

Perhaps no single piece of cycling equipment has undergone more rapid and radical design changes than aero helmets over the past 15 years. We’ve seen everything from tails that extend to the lower back to lids that are completely round, almost like a BMX or skateboard helmet. We’ve gone from tails with sharp, pointy edges to more rounded shapes with Kamm tail or virtual foil designs. Jungnickel has no idea what we’ll see next, but he says the tails are here to stay.

“A few years ago, there was a design fixation with the way riders move their heads around,” he says. “That led to that generation of round helmets with no tails. Those performed equally as well in all head positions; unfortunately, they were also equally as poor in all head positions. It just wasn’t a fast shape.”

But what about the first point of contact the aero helmet has with the wind? The visor, or lack thereof, has a big impact on the overall aerodynamics of a helmet, and it’s the one thing most manufacturers have the least control over.

“It’s really easy to mess up the visor,” Jungnickel says. “It’s really hard to make a good visor, optically, so most helmet brands rely on third parties. That means the curvature of the visor is beyond their control, and if the shape is a little o it can actually hurt the overall performance of the helmet.”

So while a visor might “look” faster, in many cases a good pair of sunglasses is a faster option. And that’s not to mention the cooling benefits of not having half your face covered.

Aero Road

From frames to handlebars to helmets, “aero road” is all the rage right now—and for good reason. Advances in aerodynamic testing and computational fluid dynamics have helped engineers push the limits of traditional “road” products so that they’re almost as fast as time trial-specific equipment. Aero road helmets have become the go-to option for Tour de France sprinters and Kona contenders alike, as the aero gap between them and full-on TT helmets closes rapidly.

“It’ll be interesting to see how those two categories converge in the future,” Jungnickel says. “Most TT helmets cover the ears—and that’s a real aero benefit—but that’s the only area we see a substantial difference in drag. For a hot race like Ironman Hawaii, an aero road helmet makes a lot of sense.”