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Giro Synthe helmet



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

At every product is thoroughly tested for as long as it takes to get a proper insight into how well it works. Our reviewers are experienced cyclists that we trust to be objective. While we strive to ensure that opinions expressed are backed up by facts, reviews are by their nature an informed opinion, not a definitive verdict. We don't intentionally try to break anything (except locks) but we do try to look for weak points in any design. The overall score is not just an average of the other scores: it reflects both a product's function and value – with value determined by how a product compares with items of similar spec, quality, and price.

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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 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.


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

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Make and model: Giro Synthe (available January)

Size tested: Blue

Tell us what the product is for, and who it's aimed at. What do the manufacturers say about it? How does that compare to your own feelings about it?

Giro say:

"The Synthe is the pinnacle of road helmet design. It offers impressive cooling power, minimal weight, supreme fit and streamlined aerodynamic efficiency. It is a true synthesis of all features a modern rider wants in a high performance road racing helmet.

"The difference is clear in the wind tunnel '' our extensive testing reveals that the Synthe is nearly as efficient as the fastest time trial helmets. But the Synthe's greatest attributes are comfort and ventilation. At its heart you'll find our Roc Loc Air fit system. Micro adjustments allow you to custom tune tension and fore-aft tilt with one hand and a patented design suspends the helmet over the top of the skull, allowing airflow to pass freely over your head. Cooling power is further boosted by elaborate internal channeling and a series of massive vents; the Synthe sets a new bar for ventilation.

"You no longer need to choose between aerodynamics and cooling power '' with Synthe you get everything, all wrapped up in a compact and sleek silhouette."

So, Giro say that the Synthe is a top-level road helmet with added aerodynamic efficiency.

Tell us some more about the technical aspects of the product?

Giro list these attributes:


234g (CE Medium)


Wind Tunnel-Aided Design for Aero Efficiency on the Road

Integrated Aero Mesh Panels

Eyewear Docking Ports

X-Static Padding

Featherweight Webbing with Slimline Buckle


In-Mold polycarbonate shell with EPS liner


Roc Loc Air


19 vents, internal channeling

Rate the product for quality of construction:
Rate the product for performance:
Rate the product for durability:
Rate the product for weight, if applicable:
Rate the product for comfort, if applicable:
Rate the product for value:

If you want value, don't go for a top end helmet. You can get a big chunk of the performance at a fraction of the price. But if you want the very best performance, the Synthe is right up there.

Tell us how the product performed overall when used for its designed purpose

I can't comment on the aerodynamics but this is a lightweight and airy helmet that's super-comfortable in use.

Tell us what you particularly liked about the product

The cooling and the lightweight. It's a bit of a cliché but you hardly feel like you're wearing a helmet.

Tell us what you particularly disliked about the product

Most people will struggle with the £200 price tag.

Did you enjoy using the product? Yes.

Would you consider buying the product? It's expensive but I'd consider it because it really is a bit special.

Would you recommend the product to a friend? Yes.

Anything further to say about the product in conclusion?

Price aside, the Synthe definitely warrants a 9. You could easily argue that the price should bring that down to an 8 but the modal category score we've given is 9 so we'll go with that on this occasion because it is an exceptional helmet.

Overall rating: 9/10

About the tester

Age: 43  Height: 190cm  Weight: 75kg

I usually ride:   My best bike is:

I've been riding for: Over 20 years  I ride: Most days  I would class myself as: Expert

I regularly do the following types of riding: commuting, club rides, sportives, general fitness riding,


Mat has been in cycling media since 1996, on titles including BikeRadar, Total Bike, Total Mountain Bike, What Mountain Bike and Mountain Biking UK, and he has been editor of 220 Triathlon and Cycling Plus. Mat has been technical editor for over a decade, testing bikes, fettling the latest kit, and trying out the most up-to-the-minute clothing. We send him off around the world to get all the news from launches and shows too. He has won his category in Ironman UK 70.3 and finished on the podium in both marathons he has run. Mat is a Cambridge graduate who did a post-grad in magazine journalism, and he is a winner of the Cycling Media Award for Specialist Online Writer. Now over 50, he's riding road and gravel bikes most days for fun and fitness rather than training for competitions.

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