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Home / Gear / Bike / Helmets / Road, aero road and TT cycling helmets: How much difference does the type really make?

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

Aiming for a season of PBs but unsure about which type of helmet to wear for the bike leg? Here we analyse the pro and cons of each type (road, aero road and TT) of lid to find the best helmet for you

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 2019 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, which are…

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? Let’s find out, starting with a visit to the Boardman Performance Centre’s new wind tunnel.


We’re in Evesham facing the chilly blast of a 2.2m high fan. Our thighs are aching, our lungs are fit to burst and our Tesco duck wrap is close to coming back up again. We came armed with the question, “What’s the fastest helmet?” expecting to hop on the tri bike and briefly pedal away for each of the eight helmets we’ve brought along.

“We need to break the testing down to address different speeds, different body positions and different head positions,” says Dr. Barney Wainwright, Boardman’s head of science and technical development. “What’s best for one person isn’t best for another. So we need to think carefully about how we test.” What follows is a three-hour interval session, riding each helmet in two head positions, at speeds of 35km/h and 45km/h and at two yaw angles for a recorded 60sec period in the set position to produce eight measures for each helmet.

Why is because each helmet performs differently in crosswinds and in a variety of aero positions, as well as at different speeds. While every brand outwardly states they have the fastest helmet, what the Boardman Performance Centre now allows athletes to do is cut through the marketing spiel and assess which helmet really is faster for them. We’re lucky to be the world’s first media outlet to enter the tunnel with a helmet collection, featuring aero road helmets from Specialized, Scott, Poc, Giro, Endura and Bell, the B’Twin Road R 500 road helmet and the TT Kask Mistral.


Our wind tunnel results soon highlight the swiftness of a TT lid compared to its aero road and trad road rivals, with the Kask Mistral outgunning 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.

Unsurprisingly, the Kask Mistral TT was the fastest overall in the tunnel, saving eight watts over the Scott Cadence on average but a mighty 23 watts over the otherwise-strong Cadence in the ‘high’ aero position on the TT bars at 0° yaw angle and 45km/h (90secs over a 40km bike leg, 6:45mins for Ironman). This is where the importance of helmet choice becomes clear. Six minutes is plenty of time to hand your rival that final Kona qualification slot.

Yet the results aren’t significantly better when the TT Kask Mistral and the aero road S-Works Evade II do battle, a 32sec average across all of the testing variables over a 40km bike leg and just 25secs at the low aero position at 45km/h. With aero road helmets continuing to narrow the aero gap, are the days of the heavier, more cumbersome, less versatile and potentially aero-hindering TT helmet numbered? “There’s still a place for a longer TT-dedicated helmet,” says Specialized’s lead product manager Alex Jerome, “though the applications will be much more limited. Better education and testing to inform the optimal positions and use-cases for these helmets will be needed, however.”

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. “While there are positions and athletes that are faster with our TT helmet, it often takes a tunnel session to find and validate that position,” says Jerome.

Do I need an aero helmet for triathlon?


A major convert to aero road helmets for both training and racing is David McNamee, the fastest British athlete ever at the Ironman World Championships in Hawaii and a man with two consecutive Kona third-place finishes.

“Helmet choice can make a massive difference in racing, especially over the 180km Ironman bike leg,” says the Scot. “When I was in the velodrome last time the first thing we tested were eight helmets. The fastest on my head was the aero road Oakley ARO 7. I was surprised about how big a difference there was between helmets; it was 15-20 watts between the Oakley and the worst performer. I now use the ARO 7 for all my races no matter the elevation, temperature and distance. Finding a helmet that breathes is obviously important for races in hotter climates, and the ARO 7 I used in Kona provides good ventilation for all conditions.”

Specialized’s Jerome continues the ventilation theme. “To be able to quantify ventilation performance, we needed to create a new set of tools, including a digital thermal head-form that allowed us to quantify the performance of individual vent design decisions in real time in our Win Tunnel. Did we burn some helmet pads for science? Absolutely. Did we learn more than ever about helmet cooling? Yes.”

The Specialized/S-Works’ Evade II was the fastest aero road helmet for us in the tunnel, excelling at the higher speed of 45km/h especially. It also performs out on the roads, offering ventilation and a transition-friendly buckle. “We’re seeing many more triathletes, including our pro’s, migrate towards the Evade II for most races as it offers more robustness to the variety of head positions encountered during a race,” says Jerome.

Aero road helmets: 9 of the best reviewed


So do traditional road helmets still have a place on the tri race course? A key positive of the standard road helmet is their affordability – with prices starting at £30 for a decent performer from B’twin and Oxford Products – 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.”

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, 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 220’s aero guru Matt Bottrill.

Budget road cycling helmets: 11 of the best under £80 reviewed

Looking to tomorrow’s helmets, the big change in helmet design could be customisable sizing, with Hexo just starting to print individually-sized helmets using 3D scanning. After a five-year design process involving 3,200 test helmets, the founder of Hexo, Oxford grad Jamie Cook, believes the benefits are an enhanced fit, aerodynamics and, crucially, increased safety, via its single hexagonal cell construction that disperses the impact of a crash more significantly than foam. So has the future of helmet design arrived already? Watch this space.


6. POC Ventral Spin

  • £270

The 250g Spin has decent airflow from its vast 13 vents and comfortable straps, but it seriously underperformed in the wind tunnel for a helmet with a £270 price tag. The unique Poc style divides opinion but, for us, the masses of exposed white EPS foam and straps give it a cheap overall aesthetic.

Best aero position: Lower speeds, low aero position, 0° yaw angle

Least effective: Higher speeds, low aero position, 0° yaw angle

Average 40km time: 1:00:16

5. B’Twin Road R 500

  • £30

The Road R has modern racy looks and the 17 vents help keep you cool on hot days. The outer shell is in-moulded, even at the rear and around the bottom surface, which makes it robust in day-to-day life but it does take the weight to 320g. The rear ratchet retention system is crude but overall it’s an amazing value lid.

Best aero position: Higher speeds, low aero position, 0° yaw angle

Least effective: Lower speeds, low aero position, 0° yaw angle

Average 40km time: 1:00:11

Buy from www.decathlon.co.uk

4. Scott Cadence Plus

  • £170

The 280g weight is higher than most but neat features include MIPS and the addition of winter bungs, which can be shoved into the ventilation channels on colder days. The internal padding is limited and the tunnel results varied wildly (see below).

Best aero position: Lower speeds, high aero position, 10° yaw angle

Least effective: Higher speeds, high aero position, 0° yaw angle

Average 40km time: 1:00:07

3. Giro Vanquish MIPS

  • £219.99

The fairly heavy 355g Vanquish MIPS is unique among the competition here as it comes with a magnetic Shield Visor. There’s good clarity but a clear gap between face and visor, which gave us concerns about detritus flicking up. Yet the helmet itself offers sound ventilation via its 10 well-placed vents, there’s MIPS and a comfy ratchet.

Best aero position: Lower speeds, high aero position, 0° yaw angle

Least effective: Lower speeds, high aero position, 10° yaw angle

Average 40km time: 59:59

2. Specialized Evade II

  • £200

With a narrow frontal profile and streamlined tail, the updated 246g Evade II instantly feels fast on the roads. The 11 deep, internal air channels are an improvement over the original, and the magnetic buckle is the best here in transition. We would’ve liked to have seen MIPS and the fixed straps are a little odd.

Best aero position: Higher speeds, both high and low aero positions, 0° yaw angle

Least effective: Lower speeds, high aero position, 10° yaw angle

Average 40km time: 59:54

1. Kask Mistral TT

  • £320

The fit of the 345g Mistral is very comfy, and the internal pads and the lateral covers for the ears are really embracing. The wind- tunnel results are almost uniformly impressive, only falling behind the aero road competition when slowing down in crosswinds and at a higher head position. But the ventilation can’t compete and it suffers in hot conditions.

Best aero position: Higher speeds, high aero position, 0° yaw angle

Least effective: Lower speeds, high aero position, 10° yaw angle

Average 40km time: 59:22

Buy from www.wiggle.co.uk


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