Aero helmets for triathletes – how and why to use them

Aero helmets will turn heads, and make you more aerodynamic on the bike leg. We explain how TT helmets can help you reach T2 faster

Why triathletes should consider aero helmets (Image:

The purpose of a cycling helmet is to protect your head if you crash, but aero-savvy riders realised that, with some clever shaping, a covered head could be faster through the air than a bare one. 


Lids designed for improved aerodynamics had appeared in triathlon as far back as the mid ’80s, most notably helping Scott Tinley to Hawaii victory in 1985. But despite the potential benefits they offered, they were only adopted by a relatively small handful of athletes.

The tipping point for aero helmets came with Greg Lemond’s 1989 Tour de France-winning time trial ride. Wearing a Giro Aerohead helmet and using tri-bars, he demonstrated the importance of aerodynamics by gaining 58secs on Laurent Fignon over the final 25km stage and taking the yellow jersey. That moment marked the beginning of biking’s aero arms race.

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Through the ’90s, aero helmets were largely just fairings to smooth airflow and offered little or no protection to the riders’ heads. Gradually the helmets’ tails grew longer and visors were added, but the biggest change came in 2003 when cycling’s governing body, the UCI, ruled that any helmet worn for racing must protect the rider’s head, meaning aero lids had to incorporate bulky expanded polystyrene cores.

Since then, the designs have been tweaked and refined as manufacturers’ understanding of aerodynamics and real-world rider positions have improved. The most noticeable change saw tails truncated to reduce the drag generated by dropped heads, for example, the Kask Bambino (pictured above), unveiled in 2012. But the developments have also fed back into standard road helmet design, with aero shells and shaping being applied to improve their performance in the wind, creating a wider range of options for faster headgear to suit more courses and conditions.

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The development process behind an aero helmet is a long and convoluted affair, as Rob Wesson, director of helmet creation at Giro, explains. “The first stage is to look at what we’ve done in the past and make comparisons. We’ll then go into our small, on-site tunnel to test our ideas, start gathering data and finding gains. We also use Computational Fluid Dynamics (CFD) and Computer Aided Design (CAD) to test new ideas.

“[From there] we’ll move into a larger tunnel and, once we’re satisfied aerodynamically, the helmet will go to the industrial design team. We’ve got certain aesthetic guidelines to meet because you could make a really fast helmet, but if it looks ridiculous it won’t be successful. There’s always a bit of give and take, but finally we’ll go back in the tunnel, subject prototypes to impact testing and then they’ll go out to our athletes.”

How and why to use an aero lid

All things being equal, a rider in a correctly fitted aero helmet will be faster than the same rider wearing a standard bike helmet. An aero helmet optimised to a rider’s position can be worth 10–15 watts according to the aero experts at Drag2Zero, which over the course of an Ironman bike leg could result in time gains measurable in minutes.

For such a relatively inexpensive piece of kit, compared to a new wheelset or bike, an aero helmet is potentially the best bang for your buck in terms of aero gain.

There are caveats though. And the first is that the helmet has to be well fitted to the rider. The tail of the helmet should transition smoothly to the rider’s back, with as small a gap as possible. If this isn’t the case or you tend to move your head a lot as you ride, your flashy aero helmet could actually be slowing you down. This especially applies to long-course triathletes whose head position may change due to fatigue and failing concentration during the bike leg.

Try a number of helmets, take side-on shots of you wearing it on the turbo, but remember to test yourself when you’re fatigued as well as when you’re fresh. Many athletes will find a stubbier-tailed helmet or even an aero road helmet, such as the Giro Air Attack that Leanda Cave wore to Kona glory in 2012, a better and more versatile option.

The next factor to consider is overheating. An aero helmet will always be hotter to ride in and, for an Ironman bike leg in hot conditions, overheating can easily cost you more time than the helmet will save. Remember, Chrissie Wellington didn’t wear an aero helmet for any of her Kona triumphs and her bike splits weren’t too shabby.

As a triathlete, you’ve also got to consider transition. A fiddly visor, stiff earflaps or a tricky-to-access cradle adjustment dial can easily cost you a chunk of time. Things like these may not be such a big deal over a long-course race, but for sprint and Olympic-distance events, these factors do need to be offset against the diminished aero time gains for the shorter bike legs.

Finally, don’t just save your aero helmet for race day. Like all race kit, it’s only by training in it that you can be 100% confident that it’s right for you. Is it comfortable? Do you overheat in it? These are questions you can only answer after hours spent on the road.

If you feel self-conscious wearing an aero helmet, enter some cycling time trials; they’re one of the only events where you’ll get funny looks for not wearing headgear that looks like it’s come from Battle of the Planets.

<a title=”Continue reading (2/2)” href=”–how-and-why-to-use-them/” style=”display:none” ” style=”display:none” our guide to aero helmets (2/2)


We continue our guide to aero bike helmets for triathletes…

The future

Looking back to the Giro Aerohead (which still performs admirably in the wind tunnel and is legal to race in), the changes over the 25 years since it appeared have hardly been dramatic. Every now and then some experimental designs materialise that buck the traditional shape.

Most recently the Darth Vader-like POC Tempor caused a bit of a stir, but you’d have to be pretty self-confident to wear one, especially in orange. Tri-friendly tweaks, such as the external adjustment dial and magnetic buckle included on the Lazer Tardiz (below), are always appreciated but are hardly game-changers.

Rob Wesson believes that there will be more steady progression in the years to come. “There will certainly be experimentation with the shape. We’re already factoring course profiles and weather patterns into our designs and this will only become more sophisticated.

“Every time we go in the tunnel we learn a bit more and can make a few tweaks. There won’t suddenly be any crazy shapes though; it’ll be evolution not revolution. It’s worth looking at the automotive industry; they slowly tweak their models towards the ideal.

“You could have a really great idea and it could work really well but, if the market isn’t ready for it, it’ll fail. Change will continue to be incremental.”

If the shape of aero helmets is going to evolve slowly, what other developments could we see? We’re certainly hoping that manufacturers will continue to tweak vent placement and design or even develop new cooling solutions in the quest for the Holy Grail of ventilation that doesn’t compromise aero integrity.

A guaranteed non-misting visor would also be fairly high on our wish list. With the technology already appearing in ski goggles, a head-up display (HUD) for visors is surely a possibility. For keeping a solid head position, HUDs definitely make sense. It’ll be interesting to look back in another 25 years and see how different the cutting-edge helmets on the Queen K Highway are compared to 2015’s designs.

Aero helmet essentials

Wind tunnel data isn’t the only thing to consider when it comes to picking an aero lid…


Designed to slide along the road if you crash and slip through the air as you ride, the shell is what gives a helmet its aerodynamic profile. The shape will generally be a teardrop, but there’s considerable variation when it comes to tail length. Most manufactures opt for a smooth surface but some use golf ball-like dimples, claiming they create even more zip.


One of the key determining factors as to how well a helmet will perform for any given rider is the shape and length of its tail. Long tails can be very aerodynamic provided they stay flat against your back but, if you drop your head or don’t ride with a flat back, any gains can easily turn into losses. A stubbier tail or tail-free helmet could be a better choice.


The expanded polystyrene (EPS) foam is what absorbs the impact energy of a crash and is designed to be sacrificial. This is why you should diligently check your helmet after a crash, or if you drop it, even if there’s no visible damage to the shell.


On an aero helmet, vents are always going to be a compromise between cooling and aerodynamics. By sucking in air they generate turbulence, and therefore drag, but without any ventilation you’re likely to overheat.


Logic says that a visor smooths out the frontal profile of your helmet and face and should therefore decrease drag. However, independent wind tunnel testing on some designs has found they’re faster with the visor removed. You’ve also got to factor in potential overheating and fogging issues but, on the other hand, they look cool.

Cradle and straps

Like a conventional helmet, the cradle secures the helmet to your head and is usually adjusted using a ratchet, dial or a similar mechanism. Straps tend to be fairly standard too but, if you’re in the pursuit of marginal gains, trim the ends down once they’ve been correctly adjusted.


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