Giro Synthe helmet

The Giro Synthe is a new aero road helmet that's lightweight, comfortable and very well ventilated.

This is Giro's top end helmet that debuted on the heads of riders from BMC, Katusha and IAM Cycling at the Tour de France earlier in the year. They call it the Synthe because they reckon it synthesises all the features you'd want in a high-performance road helmet: a low weight, plenty of ventilation, a good fit and aerodynamic efficiency.

The easiest of those to quantify is the weight, so let's deal with that first. Our medium sized test model hit the road.cc Scales of Truth at 223g which, in a radical break from tradition, is actually lighter than the manufacturer's own figure of 234g.

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That's impressively light, just 27g more than the non-aero Giro Aeon /content/review/114542-giro-aeon-helmet and considerably lighter than Giro's Air Attack aero lid. The last place you'd want to get involved in a grams arms race is in safety equipment, but the fact that the Synthe feels so light certainly adds to the comfort.

Speaking of comfort, the Synthe has plenty on offer. That's largely down to the use of Giro's Roc Loc Air fit system which is adjusted via a clicky wheel. The Roc Loc Air is a flexible plastic cradle that attaches to the helmet body at the back (where you can choose from three different height positions) and the temples, continuing right across your forehead and then backwards across the top of your head.

This has two key effects. First, by surrounding the head totally, the Roc Loc Air system means the helmet fits the vast majority of head shapes.

Second, it lifts the EPS (expanded polystyrene) body of the helmet off your head very slightly. This does away with the need for much padding – there's just one X-Static anti-microbial pad across the forehead – and allows air to flow easily through the helmet's internal channels.

In terms of ventilation, this is one of the best helmets I've ever used. Giro reckon that using a heat-sensing headform reveals the Synthe to be cooler than the existing Aeon and nearly as cool as a bare head. After using it extensively over many weeks since August, including a stint in the South of France, I can certainly believe that.

As I've mentioned, the Synthe is designed with aerodynamics in mind – like pretty much everything else in the road bike world at the moment – and it's aero considerations that have led to the distinctive 'aero mesh' perforated panels on the sides of the helmet.

Giro reckon that these reduce drag by covering the edges of the side vents. They also say that the holes in the panels alter the boundary layer of air in this area by slowing down the movement of air from the inside to the outside of the helmet, improving the aerodynamic efficiency.

"Using Wind Averaged Drag, a formula that takes into account 72 different yaw angles and calculates a single drag measurement for a standard head angle of 30 degrees and speed of 25mph, the Synthe is more aerodynamically efficient than any road helmet [we] tested, including the acclaimed Air Attack," say Giro.

We can't validate any aero claims so you can either take 'em or leave 'em. If true, we'd struggle to see why anyone would now buy the Air Attack.

Those large holes at the front of the aero mesh panels are for docking your eyewear. I tried a whole load of different models in there and they all fitted fine although some were more rattly than others. My Oakleys sat in there a treat – absolutely rock solid even when climbing out of the saddle.

Verdict

Lightweight, comfortable and very well ventilated helmet designed for aerodynamic efficiency