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Best aero road helmets: tunnel- and road-tested

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We took nine aero road helmets out on the road and into the wind tunnel to see which one was the best overall

We took nine aero road helmets out on the road and into the wind tunnel to see which one was the best overall (Image credit: James Huang/BikeRadar)
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The Bontrager Ballista won our inaugural aero road helmet shootout, posting nearly the best wind tunnel performance of the group while still offering very good ventilation characteristics and nearly the lowest retail cost

The Bontrager Ballista won our inaugural aero road helmet shootout, posting nearly the best wind tunnel performance of the group while still offering very good ventilation characteristics and nearly the lowest retail cost (Image credit: James Huang/BikeRadar)
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Our non-aero benchmark was the Specialized S-Works Prevail, which actually turned out to be fairly aerodynamic while also being surpremely well ventilated and exceptionally light

Our non-aero benchmark was the Specialized S-Works Prevail, which actually turned out to be fairly aerodynamic while also being surpremely well ventilated and exceptionally light (Image credit: James Huang/BikeRadar)
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We did all of our aerodynamic testing at the FASTER wind tunnel in Scottsdale, Arizona

We did all of our aerodynamic testing at the FASTER wind tunnel in Scottsdale, Arizona (Image credit: James Huang/BikeRadar)
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The helmet that started the aero craze, the Giro Air Attack, unfortunately finished last in the testing with surprisingly poor aerodynamics as compared to newer competition plus distinctly mediocre ventilation characteristics

The helmet that started the aero craze, the Giro Air Attack, unfortunately finished last in the testing with surprisingly poor aerodynamics as compared to newer competition plus distinctly mediocre ventilation characteristics (Image credit: James Huang/BikeRadar)
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The Giro Synthe tested surprisingly poorly in the FASTER wind tunnel in Scottsdale, Arizona - the same tunnel where the company launched the model. Testing at a higher wind speed may have helped but either way, it's very well ventilated and very light

The Giro Synthe tested surprisingly poorly in the FASTER wind tunnel in Scottsdale, Arizona - the same tunnel where the company launched the model. Testing at a higher wind speed may have helped but either way, it's very well ventilated and very light (Image credit: James Huang/BikeRadar)
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Giant' new Rivet looks the part of an aero road helmet but didn't fare so well in the wind tunnel

Giant' new Rivet looks the part of an aero road helmet but didn't fare so well in the wind tunnel (Image credit: James Huang/BikeRadar)
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The POC Octal Aero surprised us for its ability to move air across your head at both high and low speeds despite having a nearly completely solid shell

The POC Octal Aero surprised us for its ability to move air across your head at both high and low speeds despite having a nearly completely solid shell (Image credit: James Huang/BikeRadar)
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The Bell Star Pro features vents that you can open and close at will. Doing so doesn't change the aerodynamic performance, however, and ventilation is poor either way

The Bell Star Pro features vents that you can open and close at will. Doing so doesn't change the aerodynamic performance, however, and ventilation is poor either way (Image credit: James Huang/BikeRadar)
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The Specialized S-Works Venge is showing its age but it still tests very well in the wind tunnel

The Specialized S-Works Venge is showing its age but it still tests very well in the wind tunnel (Image credit: James Huang/BikeRadar)
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Kask's new Protone rounded out the podium with a great balance of aerodynamic performance and ventilation. The very high price is a drawback, though

Kask's new Protone rounded out the podium with a great balance of aerodynamic performance and ventilation. The very high price is a drawback, though (Image credit: James Huang/BikeRadar)
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The Louis Garneau Course helmet may not look particularly aero with its distinctly open architecture but the wind tunnel proved that the shape works

The Louis Garneau Course helmet may not look particularly aero with its distinctly open architecture but the wind tunnel proved that the shape works (Image credit: James Huang/BikeRadar)

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:

Aerodynamics

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.

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 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.

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.

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.

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.

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.

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?

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.

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.

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."