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Giro Synthe MIPS II Helmet



Solid and safe-feeling helmet that looks good, but a bit heavy for its high price, and you might not get on with the cradle
Substantial build
Cools well
Looks good
Relatively heavy
Relatively expensive

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 MIPS II helmet is sturdily safe, good looking and nicely made, but it's also a little heavy and expensive. Also, while the overall shape and fit is great, I personally found the cradle became uncomfortable as rides went on.

The Synthe has some impressive features. Obviously it has the MIPS system to allow a degree of 'float' between the outer shell and the bit strapped to your head (which helps reduce sudden, damaging rotations during a crash), but beneath the skin there's more.

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The Synthe hides an 'SL Roll Cage' skeleton inside its expanded foam padding, to better keep it in one piece under impact, while the job of securing the whole thing to your head goes to a Roc Loc 5 Air cradle that gives two-way tuning. That just means the rear band can be moved up and down the back of your skull, as well as cinched in tight with the usual dial.

The wide straps are easy to adjust both under your ears and at the buckle, and sit flat and comfortably. The X-Static padding is fairly minimalist both in thickness and area, but doesn't seem to suffer for it.

2021 Giro Synthe MIPS II Road Helmet - inside 2.jpg

Large cutouts in both the front padding and the retention band allow a decent amount of air through the otherwise broad plastic strap, and along with the 19 substantial vents, cooling seems good... although I tested this in winter. I didn't find it unusually chilly, though, and my guess is it'll also be fine – if not necessarily outstanding – in hot weather.

2021 Giro Synthe MIPS II Road Helmet - tension system.jpg

It's the sheer mass that makes me think this, as it feels pretty substantial and looks, on the scales, a little heavy. At 282g it's more than 20g heavier than the label claims (maybe that's in size small; this is a medium), and similar to some much cheaper helmets.

2021 Giro Synthe MIPS II Road Helmet - front.jpg

The Lazer Sphere MIPS, for instance, is a near-identical 280g and only £119.99, while the MET Rivale MIPS is significantly lighter at 236g, and cheaper too at £140.

> Buyer’s Guide: 19 of the best lightweight high-performance helmets

Even the Scott Centric Plus is £30 cheaper than this Giro, and at 222g it's fully 60g lighter too, yet it still has MIPS.

> All you need to know about MIPS

The overall shape of this lid suits me really well – I don't get on with very round lids, such as the Kask Mojito3, so it's obviously on the more elongated side.

2021 Giro Synthe MIPS II Road Helmet - side.jpg

The Roc Loc cradle I found trickier.

2021 Giro Synthe MIPS II Road Helmet - inside 3.jpg

While entirely comfortable at first, I found even before rides reached an hour I'd be shoving it around, trying to adjust out faint but irritating pressure points. Mostly these were at the back, and manifested just as slight sensitivities or hot spots that just got more noticeable. No matter where I adjusted the rear band, or how loosely/securely I wore it, the problem never went away.

2021 Giro Synthe MIPS II Road Helmet - Mips logo.jpg

It's odd, and I've never had this with another helmet – and I can only think it's just me. Certainly Mat didn't find Giro's Aether MIPS anything but comfortable, and that uses the same retention system.


I like the sturdy build, impressive safety features, great overall shape and good looks of this lid, and I think most people will find it comfortable and decently cool. The relatively high price and weight are a bit of a downer for everyone, though.


Solid and safe-feeling helmet that looks good, but a bit heavy for its high price, and you might not get on with the cradle test report

Make and model: Giro Synthe MIPS II Road Helmet

Size tested: Medium

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 says: "The Synthe MIPS II is an icon, updated to be cooler and more comfortable than ever before. The compact design slips through the air with ease yet offers impressive cooling power in a light-yet durable design that's been a rider favorite for years."

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

Giro says: 'It's packed with our best features, including the Roc Loc 5 Air fit system with 2-way fit tuning and integrated MIPS® (the Multi-directional Impact Protection System), the market-leading brain protection system designed to redirect rotational forces away from the brain and provide more protection in certain impacts."

Arguably the real 'market-leading brain protection system' is 'deleting Twitter,' but okay.

Rate the product for quality of construction:

Pretty neat and solid, though the EPS foam is not entirely protected under the front edge.

Rate the product for performance:
Rate the product for durability:
Rate the product for weight (if applicable)
Rate the product for comfort (if applicable)

I found the shape and padding great when first putting it on, but could never quite eliminate hotspots developing quite rapidly. Others find the same system comfortable, though, so it's probably just me.

Rate the product for value:

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

I didn't crash in it so can't really say, but it feels very secure and cools well.

Tell us what you particularly liked about the product

Quality build.

Tell us what you particularly disliked about the product

The longer I rode, the more aware of the cradle I became.

How does the price compare to that of similar products in the market, including ones recently tested on

It's a bit expensive – there's a good choice of MIPS helmets for £120-£150, and many are lighter too.

Did you enjoy using the product? For short bursts, yes.

Would you consider buying the product? No, but maybe my head is weird...

Would you recommend the product to a friend? Yes – unless their head was exactly the same shape as mine.

Use this box to explain your overall score

This is a reassuringly solid-feeling helmet with top-notch safety features, plus it's well shaped and cools well. I didn't get on with the Roc Loc retention but suspect that may just be me – the relatively high weight and price, however, are inescapable facts. It's not hard to find MIPS-equipped helmets that are both lighter and cheaper, which is why this quality lid is a 7 rather than an 8.

Overall rating: 7/10

About the tester

Age: 48  Height: 183cm  Weight: 78kg

I usually ride: Vitus Zenium SL VR Disc  My best bike is:

I've been riding for: 10-20 years  I ride: A few times a week  I would class myself as: Experienced

I regularly do the following types of riding: general fitness riding, mtb,

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Surreyrider | 2 years ago

Sturdy? I had a Synthe. For a few weeks. Then the 'roc loc' dial broke in normal use. It was fragile and made of the cheapest of the cheap plastic. Giro didn't give a s**t. Never, ever again will I buy anything from Giro. 

RobSC replied to Surreyrider | 2 years ago

Completely agree, I have an Aether and the cradle is made from super cheap plastic and the dial has also broken.  The plastic shell is also separating from the foam shell.  300 quid helmet.  Never buying Giro again

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