Your cycling helmet offers a great opportunity to improve your aerodynamics because it meets clean air. The way that the air is separated, passes over it, and meets again behind it is entirely down to its shape. By contrast, your rear mech, for instance, is in such turbulent air that gains are almost impossible and most brands ignore it in their aero quests. Switching your standard road helmet for an aero road model will save you around a minute on a 40km bike leg.
There’s no disputing that the coned time-trial (TT) helmet is the fastest option. In our tests the best of them can save a further minute over even the quickest of this group. But TT helmets are typically heavier, hotter and for race day only. A £250 TT helmet is a big investment when it only gets worn a few times per year.
Aero road helmets can – and should – offer a balance between TT and road helmets. That is, they have to be faster than a road helmet yet free from the compromises of weight and ventilation of a TT helmet. An aero road helmet that’s hot and heavy, yet not as aero as a TT helmet, is pointless; you may as well go for maximum aerodynamics. So while aero speed is really important here, we’re also looking for a helmet that you can train in and use on hot, hilly events.
What you’re looking for in a good aero road cycling helmet is a perfect balance between speed and ventilation. If
the former is too compromised, you might as well go for a light climber’s lid; if it’s too hot, then you’re better off with a TT helmet. So an aero road helmet option should present a happy medium.
While the weight of an aero road helmet is typically higher than a standard road lid, our wind tunnel tests at the Boardman Performance Centre in 2019 and this January reveal an aero road helmet can be 3:22mins faster than a vented lid over the 180km Ironman bike leg, a healthy saving for those vying for age-group honours. Much of this, of course, depends on an athlete’s abilities to keep their head in the same aero position, but the drag penalties of moving one’s head aren’t as high on an aero lid as when riding in a TT helmet.
We tested the helmets in both Lanzarote and Somerset; in the latter it became clear that aero road helmets also offer respite from off-season chills, proving that an aero road lid isn’t just for race day.
Time, then, to deliver our wind- tunnel and real-world results…
How we tested
No one likes a show off, but we’re proud to say that we’re the only publication worldwide to regularly test our aero helmets in the wind tunnel. The reason is that nearly every brand claims to produce the world’s fastest helmet, but still refuse to release the raw tunnel data from their own tests. As our wind-tunnel results show, some helmets only perform at certain angles and speeds so, while a helmet may technically be the fastest at a 20° yaw and riding at 55km/h, that doesn’t mean it performs across a range of wind directions and riding speeds.
That’s why we again found ourselves at the Boardman Performance Centre’s wind tunnel under the watch of Boardman’s head of science and technical development, Jamie Pringle, this winter armed with the best of 2020’s aero road helmets. We tested each at yaw angles of 0, 10 and 20°, and at speeds of 35km/h, 45km/h and 55km/h in a fixed position on a triathlon bike (adopting an aero tuck on the tri-bars that was neither too aggressive nor relaxed).
With tunnel testing done, we then took the helmets to the volcanic triathlon hotspot of Lanzarote to access their ventilation and real-world properties. Less glamourously, tests were also carried out on the off-season roads of North Somerset.
Once used by multi-Ironman world champion Jan Frodeno, the Vanquish MIPS is unique among the competition here as it comes with a magnetic Shield Visor. The visor gives good clarity but there’s a clear gap between that and the face, giving us concerns about detritus flicking up. Which is a shame, as the helmet offers sound ventilation via its 10 well-placed vents, there’s MIPS (Multi-directional Impact Protection System) and comfort from the Roc Loc system (the buckle is fiddly, however). The wind tunnel results (with the visor on) saw it regularly come behind only the S-Works (it was impressive at the 0° yaw angle and 35km/h speed, and was even better in an aggressive aero position), and it doesn’t feel like a 355g lid when riding. zyrofisher.co.uk
Verdict: swift and comfy, but we could give or take the visor, 85%
Buy from www.wiggle.co.ukero-helmet
Alistair Brownlee wears the Cadence Plus, but happily there are also benefits for us age-group mere mortals. There’s MIPS safety and the addition of Aero Plugs or winter bungs, which can be placed into the ventilation channels on colder days or if you’re truly seeking an aero advantage where heat isn’t a consideration. Those ventilation channels (sans bungs) do the job on the roads, yet the internal padding is somewhat limited, and the 280g weight puts it towards the higher level here. In the wind tunnel it performed well at speeds of 35km/h and at the 10° yaw angle but, strangely for such an aerodynamic-looking lid, less successfully when riding faster at 45km/h across all yaw angles. scott-sports.com
Verdict: we like the bungs and venting, but mixed tunnel scores 84%
Buy from www.tweekscycles.com
Naming a product a gamechanger is bold, especially when the aesthetic differences with competitors – the S-Works Evade – are hard to escape. So is the 263g Abus worth the billing? We’ve yet to see any useful aero data from Abus on the Gamechanger, only that it produces 23% less frontal drag than their vented option, which is a shame as that slim Evade-alike and rear thermal port suggest drag-reduction properties. It didn’t make the cut for our tunnel tests due to the lack of internal comfort, with minimal padding, an ultra slim fit and wedges of exposed EVA foam at the rear digging into our skull. The ratchet system and straps feel basic for £180, and venting is only adequate. Neat eyewear port, though. extrauk.co.uk
Verdict: one for athletes with very narrow heads only 66%
Buy from www.merlincycles.com
Forty quid for a lightweight (260g) helmet with impressive ventilation is a bargain. Forty quid for a helmet that outpunches competitors four times its price in the aero stakes is one of the biggest surprises these pages have witnessed. While it performed poorly at 0° yaw angle (i.e. into direct headwinds), the wider the wind angle, the better it performed. Our recorded segments even showed it beating the best in class S-Works Evade II at 20° yaw angle when riding at 45km/h. The ventilation is the best on test here (Ironman Lanzarote, anyone?) and it only loses marks due to the firm front padding, a tricky to adjust retention system and straps that have a tendency to loosen.
Verdict: mostly great tunnel results at a bargain price 91%
Buy from www.decathlon.co.uk
There’s a recent trend for narrow and streamlined aero road helmets (confirmed by our own wind-tunnel results here), yet Giant’s Pursuit is more bulbous, closer to a Poc Ventral than our winning Evade II. And the size and hefty 320g weight (58g more than the Evade II) are noticeable on the road, catching crosswinds and feeling cumbersome on endurance rides. Where it does impress is in ventilation at speed due to the eight sizeable frontal vents, but it struggled once the Spanish hills arrived. The padding is adequate but the small ratchet isn’t the easiest to adjust. MIPS is a welcome safety feature but there’s just too much strong competition at this price point for this to be a contender.
Verdict: good venting at speed but just too cumbersome for tri
Buy from www.tredz.co.uk
Specialized have spent plenty of time in their own Californian wind tunnel with the Evade II and our own results across the board once again confirm this (the Evade was the fastest overall on test in our tunnel sessions in both 2019 and 2020, especially at the speed of 45km/h but impressive across a range of yaw angles).
The 12 deep, internal air channels are an improvement over the original (as is the new addition of the MIPS safety system) for warmer high-intensity riding, and the magnetic buckle is great for transition speed and cold post-swim finger use. Weight with MIPS is still a lean 262g but we’d still prefer more adjustment with the side straps, which are oddly fixed in place.
Verdict: light, lean and the fastest here across the aero board 93%
Buy from www.specializedconceptstore.co.uk
Limar have made a concerted effort to move into the tri market in the last couple of years, attracting British ITU racers into the fold and adding a magnetic buckle on the chinstrap for added transition appeal for cold, post-swim fingers. Limar’s own positive tunnel testing has only extended to athletes riding on the hoods, but now our tri-bar tunnel analysis confirms that this is one swift lid, regularly coming second behind the S-Works and Giro (especially at the key 45km/h speed and 0° yaw angle). In terms of safety, there’s no MIPS protection but the retention system is secure, while venting from the 12 channels on hilly, sticky days is acceptable. Weight, meanwhile, is a decent enough 259g.
Verdict: plenty of tri appeal and success in the tunnel, too 90%
Buy from www.cyclerepublic.com
Poc’s helmets divide opinion in both style and substance, and that continues with the lean 250g Ventral Spin. Good points include the eyewear garage and easily-adjustable straps, while the airflow from the 13 vast vents (utilising the Venturi Effect, where air goes into a wide area and is pushed out through a smaller area) is decent. In lieu of MIPS, POC employs its own padding with impact protection capabilities. Onto the negatives, and the masses of exposed white EPS foam give it a cheap aesthetic, while the elephant in the room is the £270 price for something that really underperformed in the tunnel (scoring especially poorly at 45km/h). For the price, we’d be looking at a Hexr 3D custom helmet. 2pure.co.uk
Verdict: good venting but poor tunnel results for the price 67%
Buy from www.bikeinn.com
With striking looks, effective straps, comfy pads and MIPS protection, the Bell Z20 Aero has plenty going for it. But its weight of 281g is average and, for such an aero-looking lid, it largely placed mid-table in the wind tunnel (it was good at the most critical for long-course triathlon 45km/h with a 0° yaw angle, however), consistently scoring below the Specialized, Giro and, at times, the £40 Van Rysel. All of which makes us question its worth, especially when venting is compromised by the 10 small channels and the financial outlay is over £200. Despite this, it’s the helmet we’ve used the most for winter riding for the last 12 months thanks to the comfort, fine looks and chilly wind-deflecting abilities. zyrofisher.co.uk
Verdict: Top looks, high price, decent enough in tunnel 80%
Buy from www.wiggle.co.uk
How the wind tunnel results were analysed
“Although there were some exceptions, the rank order of performance of the helmets was quite consistent across the various wind speed and yaw scenarios,” says Boardman’s Jamie Pringle. “The range of differences in the aero performance of the helmets is 5.9%, which is large given that all the helmets were aero race ones.
“Consider that, for a normal 90min wind tunnel optimisation session, our typical saving in aero drag is 9-10%, but this is coming from adding up gains from a dozen changes, including bike position. That a single change of helmet can offer more than half of this total gain is remarkable.
“Yet, with a Coefficient of Drag [CdA, used to used to quantify the drag of an object] of 0.22 to 0.24 m2 region, there’s scope for improvement. The aero game has changed in the last five years and a CdA of 0.20 is common. That aero performance once was the domain of track riders, but triathletes are getting closer. A helmet’s volume can be as important as its shape and features, and helmets that fit poorly can be counterproductive. Product development that considers multiple wind scenarios and individual fit are likely to have greater impact in the real world.”
The overall verdict
For something that started out as purely a safety product, race-day helmets have developed a lot over the past decade, with removable visors, Venturi effects and thermal ports all present here. If you believe the team at Hexr 3D-printed helmets (see 220tri.com), there’ll be developments to come in the next decade but for now the tunnel and the tarmac prove that (most of) the current crop are producing comfort and speed in one lid.
Abus and Giant didn’t make the tunnel cut due to their asphalt performance, respectively, while the Poc seriously underperformed in the Boardman Performance Centre for a helmet of £270. The Scott stands out for its additional bungs for aero or thermal gains (although it strangely performed better at slower speeds), as does the Giro for its magnetic visor. But, for us,three helmets stood out for their road and wind-tunnel abilities.
The first is the Van Rysel, which has utilised Decathlon’s own wind tunnel to startling effect and produced a sub-£50 lid that holds its own against £200 options. Sort out the straps as this is a solid gold pick. There’s little to separate the Limar and S-Works in terms of price, road feel and weight, but the S-Works again edges this test for its MIPS and commanding tunnel scores.