Road, aero road and TT cycling helmets: How much difference does the type really make?

Long gone are the days when a bike helmet was purely for protection, a polystyrene lump to satisfy the race regulations and your own peace of mind. Cut to 2024 and a wisely-chosen race helmet is one of the most affordable and significant ways to limit your drag, especially as the helmet is one of the first parts of your body (which accounts for 80% of drag when riding) to disrupt airflow.

If kit cupboard space and financial outlay were limitless, we’d all own three bike helmets from each helmet genre.

Road, aero road and TT helmets explained

The traditional road helmet is the lightest of the three and features more venting channels for increased airflow, making it suitable for training and hillier, hotter races.

Next up is the TT/tri-specific helmet, that seventies sci-fi-recalling long-tailed choice with limited venting and maximum drag reduction, long proven to be the fastest in the wind tunnel but with a weight and comfort penalty.

Finally we have the aero road helmet, which burst onto the scene in 2012 in the form of the Giro Air Attack. They’re a winning hybrid of traditional road helmets and TT lids, faster than standard lids but free from the weight and ventilation compromises of a TT helmet.

So which lid for which race? And are the aero gains as lofty as the brands and PR departments have us believe? To inform your choice, we’ll draw on data we’ve collected from three wind-tunnel testing sessions.

In 2019, we became the world’s first media outlet to enter the Boardman Performance Centre wind tunnel with a helmet collection, featuring aero road helmets and the TT Kask Mistral.

We’ve also paid two visits to the Silverstone Sports Engineering Hub. In 2024, we used the wind tunnel as the basis for our group test of the best aero road helmets for triathlon.

Pros and cons of TT helmets

Our 2019 wind tunnel results soon highlighted the swiftness of a TT lid compared to its aero road and trad road rivals. The Kask Mistral outgunned the aero road POC Ventral by 54secs and the trad road B’Twin by 48secs on average over a 40km bike leg.

Put that over an Ironman bike leg and the time reads 4mins, a major saving if you’re chasing age-group honours and qualification slots.

However, the Kask Mistral TT only marginally outperformed the aero road S-Works Evade II: by a 32sec average across all of the testing variables over a 40km bike leg and by just 25secs at the low aero position at 45km/h.

Since then aero road helmets have continued to narrow the aero gap. The scarcity of TT helmets in elite triathlon suggests the days of the heavier, more cumbersome, less versatile and potentially aero-hindering TT helmet are numbered.

Also key to remember is that our wind-tunnel tests were performed in a position where our upper body was static, in contrast to the demands of a triathlon when fuelling, aid stations, climbing and cornering are all challenges.

Pros and cons of aero road helmets

Our most recent wind tunnel session in summer 2024 and our real-world testing indicate that aero road helmets offer the best overall performance for triathlon.

Most aero road helmets permit greater airflow than a TT lid in summer racing keeping you cooler. When it’s colder, aero helmets keep our icy drafts better than a vented road helmet. 

You should also consider how well the retention system works, how easy the buckle is to clip on and off and, of course, how protective it is. 

All helmets for sale in Europe, North American and Australia must meet increasingly uniform minimum safety standards. 

You can also gauge how well a helmet might protect your head in a crash from its Virgina Tech safety rating and from the presence of anti-concussion technology like MIPS.  

The main disadvantage of aero road helmets compared to standard helmets is their cost. The cheapest helmet in our aero helmets was the £99.99 Van Rysel Road Bike Helmet FCR. That’s twice as much as quality traditional road helmet. And you can spend hundreds on range-topping models: the Kask Elemento will set you back £335 at full price.

Can you wear a vented road helmet for triathlon?

So do traditional road helmets still have a place on the tri race course? In brief, the answer’s yes.

Vented road helmets are usually cheaper, lighter and cooler than TT helmets and aero road helmets. In the right position, they can be faster too.

A key positive of the standard road helmet is their affordability. Prices start at £30 for the best budget helmets compared to over £100 for most aero road helmets (that said, we’ve used the £13 Carnac Aero Road for long-course racing and it performed well).

A standard road helmet may be slower than the aero road or TT options. But you’ll be less likely to pay severe aero penalties compared to a poorly-positioned TT helmet with its tail pointing skywards.

And if you’re thinking of racing the Alpe d’Huez Triathlon, Helvellyn on a hot day, or in the crosswinds of Ironman Lanzarote then the benefits of a traditional road helmet will become clear.

Four-time Ironman world champ Chrissie Wellington famously wore a standard road instead of a TT helmet in Hawaii, citing the extra comfort and ventilation offered. “It doesn’t have to be the all-singing and dancing ‘aero’ kind,” says Wellington.

“A regular ‘brain bucket’ will protect your head. Just make sure it’s passed the necessary safety tests.”

You’ll feel the downside of this ventilation on a cold winter ride, though, which may make the vented road helmet less versatile.

Surprising aero performance

As our wind tunnel tests show, the trad road helmet can also perform in the aero stakes.

With a price tag of £30, we expected B’twin’s Road R 500 to be destroyed in the wind tunnel by the loftier contenders in our 2019 testing. But it was consistently faster than POC’s £270 Ventral throughout.

So the key is to know your aero position and expected course types, average race speed and likely wind types come your ‘A’ race this season and pick your helmet accordingly.

There’s also the issue of finding a helmet that fits you correctly. “Head position and a correctly fitting helmet are the key elements you need if you’re going to go faster,” says aero guru Matt Bottrill.