Giro's new Aeon helmet mixes the DNA of its two top-end road helmets – the Ionos and Prolight – into a single model that offers the superb ventilation of the former but the lightweight of the latter.
The weight is indeed striking for a helmet that appears to make no compromises in its quest to shave grams. Our CE-certified small sample weighs just 190g, making it just less than 30g heavier than an equivalent Prolight (but still about 100g lighter than an Ionos) while CPSC versions will tack on only another 30g or so.
According to Giro product manager Warren Gravely, one of the main ways the company was able to bring the weight of the Aeon down so low was with the new Thermoformed SL roll cage, a one-piece internal reinforcement structure 49 percent lighter than the multi-piece fiber composite one in the Ionos. Interestingly, the Thermoformed SL structure is made of the same polycarbonate material as the Aeon's outer shell – effectively making the new helmet a dual-layered helmet with a shell within a shell.
Additional weight saving measures include size-specific (and safety standard-specific) foam densities, ultralight webbing material borrowed from the Prolight, and slimmer lockable sliders that still allow for full adjustment like the Ionos but with fewer grams. Though it wasn't done in time for the first production runs, Giro says 2012 model year helmets will also get a slightly lighter-weight buckle.
Carried over from the Ionos is Giro's highly adjustable Roc Loc 5 retention system.
The Thermoformed SL cage also allowed for bigger vents like on the Ionos, unlike the Prolight, which had to make do with smaller ports since there was no internal structure to help hold everything together in the event of an impact. Material has been removed from right next to the rider's head for more minimal contact, too, while the deep internal channels and 25 vents are oriented more inline front-to-rear for supposedly more direct airflow while the rider is moving.
Giro hasn't conducted any instrumented headform testing on the new Aeon yet – nor any aerodynamic drag studies – but says the "perceived ventilation" should be right about even with the Ionos. We wore a new Aeon during an unusually warm Touriste Ronde van Vlaanderen the day before the pro event and while we can't say yet that it's ventilated as well as an Ionos, its noticeably better than a Prolight for sure – not to mention better looking, too.
Giro will offer the Aeon in three sizes and five standard colors – black, white, red/black, blue/black, and matte titanium – plus three limited edition versions in Rabobank, Garmin-Cervélo, and Thor Hushovd world champion themes. Retail price is US$250/€250 and worldwide availability is set for May 1 (though some US dealers may have them a couple of weeks earlier).
The Giro Aeon in Rabobank colours