Giro Synthe helmet – review

Aero road helmets have been multiplying in number, season on season, for the last few years. Most manufacturers are onto their second generation aero road lid now and it's easy to see that some real progress is being made in both design and aerodynamic terms. Giro have gone one step further with the Synthe, creating a helmet that they claim is not only best in class aerodynamically, but also as well-ventilated as their much vaunted Aeon.

Giro have made some pretty big claims with the Synthe, with one of the biggest being that it’s almost as efficient as the fastest TT helmets in the wind tunnel. The previous benchmarks in Giro’s range for aero efficiency and cooling have been the Air Attack and the Aeon respectively and Giro claim the Synthe performs better than either in those categories.

They also claim it’s faster than Specialized’s Evade, perhaps the most aero-looking (and looking is the operative word) of the aero road helmets on the market at the moment. Unfortunately at RCUK we don’t have Giro’s budget to take the Synthe and its competitors to the wind tunnel for a comparative test. So I’ll have to take Giro at their word when it comes to the aerodynamic claims.

But, as a general rule, since most wind tunnel testing is done at 50km/h (which I certainly don’t achieve on an average ride without a very healthy tailwind – or a stretch of downhill), and the resulting differences will be less significant around the 30-35km/h mark that most amateur riders can comfortably maintain, to a certain extent the aerodynamic benefits of the helmet are a moot point for us mortals. Giro say tests on the Synthe were done at 25mph (40km/h), but even that means at most peoples’ cruising speed the aerodynamic benefits will still be significantly diminished. However, the key message that Giro are trying to get across with the Synthe is that you don’t have to make a choice between a helmet that’s aerodynamic or one that’s well ventilated any more, now you can have both.

Construction-wise, there are a couple of particularly interesting things to look at. The first is the new retention system called the Roc Loc Air. The Roc Loc 5 is Giro’s standard fit system, used on the Aeon with a small dial at the back that you twist to tighten or loosen the lid. The Roc Loc Air on the other hand takes that same retention system, but lifts the outer shell of the helmet away from it, leaving a gap between head and shell for more air to flow over the head.

It’s only 3mm, but the difference is certainly noticeable and airflow in the Synthe is outstanding. It’s so good that unless it’s a warm day or you’re working extremely hard, you might even want  a headband or skull cap underneath – especially in the fresh spring weather we’ve had lately. Uphill the ventilation is a massive bonus, but downhill you learn the real meaning of wind chill.

The Roc Loc Air was used on the Air Attack as well, but what makes it so effective in the Synthe is the added ventilation. If you look at the front of an Air Attack, there are two slit-style vents on the front of the helmet and another two on top. The Synthe has five large vents at the front, two on top, two more at the side and a mesh section to boot.

The mesh section also apparently aids aerodynamics, Giro say, reducing drag by covering the edge of the side vents while the holes in the panels control the airflow’s boundary layer. Big vents on the side of a helmet apparently have a significant bearing on aerodynamics – hence why most aero helmets don’t have large, if any, vents on the side. On top of that, the two small vents at the front have been designed as docking ports for your sunglasses if you want to take them off. Smart.

Flip the Synthe over and you can see the internal channelling, also designed to aid airflow. There’s one large channel over the centre of the head supported by a complex system of minor vents, designed to make sure that no section of your head is missed before the air flows out of the similarly large vents at the back.

Fortunately, for us ‘normal’ riders, Giro haven’t forgotten about comfort either. The Roc Loc is simple to use and adjust and the cradle has three different positions, depending on whether you like it high up or low down on the back of your head.

And weighing in at 232g (for our size medium) means it’s light enough that you can almost forget you’re wearing it – always the sign of a quality helmet.

I say almost because the one thing that hasn’t changed is the straps. I’ve never been that big a fan of them as I find them a pain to adjust and difficult to get sitting exactly as I want. And once set, they tend to work themselves loose quicker than those of different brands.

Personally, I’d choose straps like those on Kask’s Mojito that have clearly been designed with more of an eye on comfort. But there’s no way a small gripe like that would stop me from buying one of these, as the Synthe is genuinely one of the most comfortable helmets I’ve ever used.

It’s also fair to say the Synthe is one of the best looking aero road helmets around, mostly because it doesn’t actually look like one.

Giro have managed to do away with the outlandish shapes and sizes and made what on first glance could easily be mistaken for a semi-covered version of the Aeon and it’s sure to appeal to a far wider audience.

It’s the sort of lid you could turn up to your local club run wearing without receiving suspicious glances from everyone else riding, so you won’t have to be prepared to sacrifice aesthetics in an attempt to glean performance gains. Plus it’s available in eight different colourways if you don’t fancy the fluoro highlighted version tested, including the same colour scheme as used by the Katusha squad.


The Synthe is sleek, comfortable, incredibly well ventilated and (apparently) pretty aero too. It’s a big step forward in aero road helmet terms as it makes the genre more accessible to the average rider who’s after comfort and acceptable looks as well as performance.

The price is high, but I’d expect to see elements of the Synthe’s technology start to trickle down Giro’s helmet range over the next 12 months, so even if you don’t fancy dropping £200 on a new helmet you’ll be able to see some of the benefits if you wait a while.

But if this is in you’re price range and you’re after a new top-of-the-line lid, the Synthe covers every base better than any road helmet I’ve ever used.

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