This article was originally published on BikeRadar.
Once a curious little niche just three years ago, the aero road helmet category has since exploded with nearly every company including at least one in its lineup. Sure, they might be fast in a wind tunnel (some less than others, we found), but aero road helmets aren’t just about speed. They still need to be well ventilated – at both high speeds and low – lightweight, comfortable and hopefully reasonably priced if they stand a chance of being your primary day-to-day choice.
So which one is the best? We evaluated nine of the top models to find out, based on the following criteria:
The appeal of an aero road helmet is its promise to help you go faster with the same amount of effort. We tested these helmets at the FASTER wind tunnel in Scottsdale, Arizona – the same tunnel Giro used in developing its highly acclaimed Synthe – at yaw angles of 0, 5, 10 and 15 degrees, and with a single head angle. Recorded values were averaged for a final composite score.
Instead of using the industry-standard 30mph wind speed, though, we tested at 20mph. Higher speeds might very well exaggerate differences in aero performance, but according to FASTER’s director of biomechanics and technology Aaron Ross, you can’t predict airflow on a linear scale. We experimented with a few of the helmets at 30mph and the rankings actually changed slightly.
Most importantly, cyclists don’t spend all day riding at 30mph. We asked the folks at Strava to pull the average speed of its entire, massive rider database to get a real-world idea of how fast we’re really going. As it turns out, male cyclists ride at just 15.6mph on average; for women, it’s 13.4mph. Even if you assume that the typical aero road helmet buyer moves faster than that – say, in a racing situation – we decided to evaluate these helmets for all-around use since that’s how they’re more likely to be ridden.
The only way to truly determine a helmet's aerodynamic performance is to take it into the wind tunnel
If aero road helmets were solely about going fast, we’d see a lot more people in full-blown TT lids. As it turns out, it’s still critically important that these helmets provide sufficient airflow to keep our heads reasonably cool.
We subjectively scored each of the helmets on their ability to move air across our heads while traveling at both ‘cruising speed’ – roughly 18-25mph – and during much faster mountain descents, all around mid-day in hot Colorado sunshine. Most of the helmets fared reasonably well, and some were downright surprising in how much air you could feel rushing across your scalp. Others, though – not so much.
Getting air to move over your head at higher speeds is relatively easy but it’s when laboring up a long, steep climb on a hot and humid summer day that we desperately need to bring in some cooling airflow, and give hot air a path to escape.
Not surprisingly, this is where most of the helmets fared relatively poorly as it’s much easier to design an aero helmet when you don’t have to account for airflow through as well as over and around the shell.
This was again a subjective scoring process based on ride evaluations on various climbs with speeds primarily hovering around 10mph.
The harsh reality is that aero road helmets are rarely things of beauty, at least until our perceptions are reset. We judged each of the helmets based purely on opinion, combining feedback from our own staff with comments from a random poll of local cyclists.
Aero helmets tend to be heavier than standard ones. The differences might seem fairly small on paper – often just 40-60g – but it’s still noticeable toward the end of a four-hour ride. As always, lighter is better.
The price range for aero road helmets varies tremendously with nearly a two-to-one difference between the most expensive and least expensive models on test here. As with the weight category, this one’s a no-brainer: less expensive is better.
First place: Bontrager Ballista (US$175 / £129.99 / €240 / AU$200, 253g)
Bontrager came to the market late with its first aero road helmet, just launching its new Ballista at the start of the Tour de France. However, its designers have clearly learned from the lessons and mistakes of others as the Ballista emerged as the best overall model we evaluated.
The Ballista finished second in the wind tunnel tests at 20mph but jumped ahead in the overall ratings on account of its excellent ventilation scores. You can legitimately feel a rush of cooling air across your head when you’re going fast, and yet the deep internal channeling, generous space at the brow, and louvered upper vents do a remarkably good job of evacuating hot air on slower climbs, too.
Sealing the deal: Ballista was nearly the least expensive helmet on test, nice and light, and one of the better looking ones, too.
Second place: Louis Garneau Course (US$240 / £155 / €180 / AU$N/A, 263g)
The Louis Garneau Course helmet may not look like an aero lid with its open architecture and generous venting but it was a solid mid-pack finisher in the wind tunnel. That hardly makes this helmet a leader if you’re solely focused on speed but the Course excelled in both high-speed and low-speed ventilation tests with superb airflow all around.
Adding to the Course’s solid second-place overall finish is its decidedly conventional aesthetics, and mid-pack pricing and weight.
Given the fantastic venting, though, this would be our number one choice if your summertime riding regularly includes ultra-hot and humid weather.
Third place: Kask Protone (US$300 / £195 / €235 / AU$N/A, 278g)
The Protone is surprising for its generous size and number of vents. The upper rear of the shell is essentially solid, though, and as is common for newer aero lids, the Protone sports an overall shape that’s very trim and compact, with a notably truncated tail that apparently creates less of an air brake effect.
Like the Course, the Protone fell mid-pack when it came to the wind tunnel tests but its outstanding high-speed ventilation brought it well up in the overall rankings. Low-speed ventilation wasn’t as good but it was still quite reasonable with only limited airflow in the restricted brow area holding it back.
The Protone did very well in the aesthetics department, too, with a bold shape that somehow manages to be both eye-catching and fast without making its wearer look like something out of a sci-fi movie. Unfortunately, this sleek Italian lid was also one of the most expensive.
Fourth place: Specialized S-Works Evade (US$250 / £160 / €230 / AU$TBC, 278g)
When compared against a field of mostly fresh-faced contenders, the S-Works Evade is starting to show its age just a bit. It’s the heaviest of the bunch and one of the most expensive, and while its high-speed ventilation is very good, it can feel stifling if you’re not moving fast enough to push air through its teardrop shape.
It’s still fast – it finished fourth in our wind tunnel testing – but more recent aero road helmets have figured out how to better balance that speed with other performance attributes, too.
Fifth place: Bell Star Pro (US$240 / £170 / £TBC / AU$300, 255g)
The Star Pro was the outright winner when it came to aerodynamics, besting the field across all wind angles tested. If speed is your primary concern, this is your choice.
Bell makes a lot of noise about the Star Pro’s intriguing venting system, which can be opened and closed on demand with a simple flick of a lever. Interestingly, though, our testing showed almost zero change in drag with the vents opened or closed.
Unfortunately, that confirms what we felt on the road – that there wasn’t that much air coming into the helmet at either high or low speeds. You can feel a draft down the sides of your noggin if you tilt your head down when really moving along but the lack of significant internal channeling, the completely obscured front shell, and minimal brow space made the Star Pro a veritable sweat box on climbs.
Long-term durability is also questionable. The venting system itself feels a bit cut-rate, and to accommodate it, the Star Pro is essentially made as two helmets that are sandwiched together – with little more than two-sided foam tape, as far as we can tell.
That all said, several testers mentioned that the Star Pro might make for an ideal helmet come cyclocross season: start with the vents closed to stay warm, and then open them up later as you generate more heat.
Sixth place: POC Octal Aero (US$300 / £250 / €TBC / AU$400, 271g)
That the Octal Aero finished third in the wind tunnel wasn’t all that shocking given its tapered profile and almost completely smooth exterior with nary a bump to disturb the oncoming air. What genuinely surprised us, however, was that it actually did quite a decent job of moving air across your head.
The Octal Aero is essentially identical to the standard Octal save for the outer shell. As a result, there’s a tremendous amount of super-deep internal channeling and quite a bit of room between the helmet and your forehead. POC has also left intact the enormous exhaust ports at the rear. Airflow at higher speeds was remarkably good, and low-speed venting was quite decent as well, provided you’re not moving too slowly.
Hurting the Octal Aero in the overall scoring was its decidedly questionable aesthetics (one person said it looked like a bowling ball), its high price (tying the Kask for most expensive on test), and relative heft.
Seventh place: Giro Synthe ($250 / £200 / €TBC / AU$400, 209g)
With fantastic ventilation at both high speeds and low, far and away the lightest helmet on test, and appealing looks that garnered praise all around, how on earth did the Synthe only manage a seventh place ranking?
Because it apparently isn’t all that fast.
As we mentioned earlier, wind tunnel testing is hardly a cut-and-dried science and there’s plenty of variability. Had we tested at more head angles, and perhaps at a higher speed, the Synthe may very well have performed better, but as it was, it finished dead last in terms of drag. In fact, it registered slower figures than a standard Specialized S-Works Prevail and in this context not being any faster than a standard helmet automatically relegates you to the back of the field.
We still like the Synthe for its overall blend of attributes but if you’re looking for speed, this might not be where you’ll find it.
[Editor's note: Giro disputes our testing methodology and resulting scoring. A statement from Giro follows at the bottom of this article.]
Eighth place: Giant Rivet (US$160 / £120 / €140 / AU$TBC, 273g)
The new Rivet is unquestionably ‘new school’ when it comes to its shape, with a dramatically clipped tail and an extremely trim profile. Three big forward vents (plus two smaller ones) and heaps of space around the brow combine with four big exhaust ports to deliver impressively good airflow at higher speeds. Ventilation at slower climbing speeds is surprisingly decent, too, and it’s the cheapest in this group at roughly half the price of the Kask Protone.
The Rivet is on the heavier end of the spectrum but what really holds the Rivet back is its disappointing wind tunnel testing: third from the bottom and, like the Synthe, slower than the Specialized S-Works Prevail. If you’re going to make compromises in terms of ventilation, there had at least better be something to show for it.
Ninth place: Giro Air Attack (US$200 / £150 / €200 / AU$TBC, 274g)
Sadly, the helmet that started the whole aero road helmet craze back in 2012 has now fallen to the back of the pack with surprisingly poor wind tunnel performance, tying the Synthe for last place in terms of averaged drag.
Adding more nails to the coffin are the Air Attack’s middling high-speed ventilation and poor low-speed ventilation (despite plenty of internal channeling), its rather humble appearances, and uninspiring weight.
It’s not exactly a bad helmet, but you could certainly do better.
Should you bother with an aero helmet at all?
We’ve gone through the trouble of determining which of these aero helmets is the best overall but one big question remains unanswered: should you even care?
No matter what kind of cyclist you are, science is science and all else being equal, wearing a helmet that’s more aerodynamic makes more sense than one that’s less so. You can go faster and further with the same amount of effort, or save energy while maintaining the same pace.
Aerodynamic benefits also increase exponentially with speed, meaning those advantages will only grow larger the faster you go. In other words, an aero helmet might not make a ton of sense if your primary concern is just getting in a good workout or making it to your favorite coffee stop, but it’s an easy choice if you’re a racer looking for every bit of help.
As always, though, not all manufacturer claims hold water. Each of these helmets is billed as generating less drag than non-aero helmets but that wasn’t the case for the Giant Rivet, Giro Synthe, and Giro Air Attack (although keep in mind that could've changed with a different test protocol). All three were actually slightly slower than our benchmark non-aero helmet, the Specialized S-Works Prevail, which is also exceptionally well ventilated and one of the lightest helmets around. This isn’t the last aero road helmet test we plan on doing, and next year’s will certainly include a bigger selection of non-aero models, too.
Just because it says 'aero' doesn't mean it is. The Specialized S-Works Prevail actually beat three of our aero road helmets in the wind tunnel
Statement from Rob Wesson, Giro Director of Helmet Development:
"Giro appreciates the time and effort BikeRadar put into this story – it’s fantastic that the media is paying attention to aerodynamics. We welcome any outside testing of our helmets, but the results are only significant when done with the same scientific rigor and practice that we ourselves put into testing and presenting results to the public.A few of our concerns:
Set up was not consistent from helmet to helmet. The test pictures show that each helmet had a different taping over the straps. Testing has shown that strapping can effect the aero scores dramatically.
What is the margin of error in the test results? For aero evaluations of helmets, the two main components of error come from the operator assembling the helmet to the head form and the error that the tunnel registers. Multiple setups and tunnel runs with the same helmet at different times in the day need to be done and evaluated to understand the baseline and confirm the overall error. Giro’s extensive testing over the years has found that total tunnel data error is approximately 10g of drag; which means that any helmets whose drag is within 10g of each other are statistically equivalent. The LG Course and Protone both get a 3, the Giant gets a 2, and the Air Attack and Synthe get 1s — however all four helmets are within 9 grams of each other and therefore equivalent. If the calculated error is much higher than 10g then it is difficult to impossible to make any valid aero claims.
Head Form Size not compatible with helmet size. We’ve testing on this headform at Faster and know that it is on the large end of a medium fit. These small size helmets clearly just don’t fit correctly. Since the helmets do not fit the headform, they are raised up much higher than where they would actually be ridden on a consumer. This is a bald headform and therefore could have a massive effect on the aero performance of each helmet versus if it was fitted to the correct size headform.
Failing to use Wind Averaged Drag.Simply averaging the results from 4 angles does not accurately represent real-world conditions. Riders statistically encounter yaw angles of 5º much more often than 20º.
Only testing one head angle. This is too limiting to actual real world scenario. Accurate testing requires at least two head angles to evaluate.
Again, we applaud the effort to do some verifiable testing. We at Giro hope BikeRadar can be part of our ongoing discussions with media and other manufacturers toward the end of designing a universal, repeatable, accurate protocol so that riders can make informed decisions when choosing their next helmet or helmets."