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Item # GIR0268

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Item # GIR0268


Why is the Giro Ionos our all-time best-selling helmet at Competitive Cyclist? It boils down to a few key points: One is its weight. Giro makes liberal use of lightweight composites to make the Ionos nearly 10% lighter than its predecessor, the Atmos. And then there's its ventilation. You get 21 huge vents -- in fact Giro states that they designed the structure of the Ionos around the vents, specifically to maximize head coolness. Giro calls it "Wind Tunnel Technology", and their testing indicates that you get 15% more airflow over your head in comparison to the Atmos. And with its Roc Loc 5, Giro's latest retention system, it's even lighter and more comfortable than ever before.

Roc Loc 5 is Giro's latest, and if you've worn it you'll know, greatest retention system. First and foremost, Giro engineers took out 40% of the weight of the popular Roc Loc 4 system at the same time they made it more adjustable and more comfortable. What's different you might ask? For starters,Giro Ionos Helmet  Detail the indexed Micro Dial on the back lets you adjust the tension to perfection with a two fingered twist. It's that simple. And the Three Position Bracket allows 15mm of vertical adjustment in the retention basket -- enough to fit any head shape comfortably. But what's comfort without ease of use? Giro facilitates quick donning of your casque with clever strap management. The retention basket has strap holders to ensure that they'll be right where you want them by the time the helmet falls into place on your melon.

The in-mold construction of the Ionos fuses the four-piece outer shell with its impact-absorbing EPS liner, allowing the two materials to reinforce each other for maximum safety. You can think of it as a super-strong exoskeleton, and it's bolstered by the composite sub-frame that runs throughout the helmet's liner and around the vents. This sub-frame provides structural support, impact-dispersion, and resistance to penetration. This complex structural design is the key to making the Ionos lighter, tougher, and more ventilated than any other helmet in the marketplace.

The Giro Ionos is available in Black/charcoal, Black/yellow, Blue/black, Matte Black/red, Matte Titanium, Red/titanium, White/silver, and Yellow/black. Small fits heads 51-55cm, Medium fits size 55-59cm, Large fits 59-63cm. By the way, if you sweat like crazy we sell replacement X-Static pads to keep the interior of your Ionos looking, feeling, and smelling fresh.

Tech Specs

[shell] plastic, foam
Recommended Use:
Manufacturer Warranty:
1 year

Size chart


Adult Cycling Helmets
 SS/MMM/LLXLAdult UniversalWomen's Universal
Head Circumference 20 - 21.75in
(51 - 55cm)
20 - 22.5in
(51 - 57cm)
21.75 - 23.25in
(55 - 59cm)
21.75 - 24in
(55 - 61cm)
23.25 - 24.75in
(59 - 63cm)
24 - 25.55in
(61 - 65cm)
21.25 - 24in
(54 - 61cm)
19.75 - 22.5in
(50 - 57cm)
Head Circumference 20 - 20.75in
(51 - 53cm)
21.25 - 22in
(54 - 56cm)
22.5 - 23.25in
(57 - 59cm)
23.5 - 24.25in
(60 - 62cm)
How to Measure:
For best results, use a tape measure to measure around your head where your hat would fit comfortably.

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Cool (literally) Helmet

  • Familiarity: I've put it through the wringer

I've been riding Giro helmets for years now, but this one takes the cake. It's not the lightest you can buy, but I rode all summer with it (100+ degree days in Tucson, AZ) and my doo-rag never once got wet with sweat. It's 'wind tunnel' affect really does buy you a nice cooling action. It complements my kit (isn't that really all that matters?) but is very functional. I've ridden with it commuting and riding a 234 mile event and it never felt heavy, hot, or noisy.

Now that winter is coming, the provided barrier is helping with the helmet, though for cold days (below freezing) I'm going to go with something else. Overall, for the price (much less than I paid for it on Realcyclist) you really can't beat it. Sorry, though I've been hit by a van while riding with it, I didn't hit the helmet so no idea about damage prevention, but it's size (compared to my old Giro) suggests I would have very good coverage of all the important bits.

Update 9/14 -

A car attempted to t-bone me and I went down, hitting my head hard on the pavement. The helmet crushed in pretty well, and I was forced to discard it. I miss it already, and will buy an updated version soon.

Love it!

    My rides are usually less than 100 miles but I've never once noticed that it was on my head. Very comfortable. I will say that it seems to create a lot of wind noise but that has only been noticable when I'm trying to listen to music

    Unanswered Question
    Avg. ride time: 5m per week
    • Average ride time is based on Strava activity over the last 3 months. Give your reviews credibility by connecting your account.

    Does this helmet meet the Australian Safety...

    Does this helmet meet the Australian Safety standard AS 2063 (silver and red sticker inside the helmet)?

    Unanswered Question

    Write your question here...Does anyone...

    Write your question here...Does anyone know where to get replacement inserts for the Giro Ionos Helmet. Love this helmet, but keep loosing the inserts when I take it off my head.

    Hi! I have vision glare issues and need...

    Hi! I have vision glare issues and need to wear a brimmed cycling cap underneath my helmet. Does the Giro Ionos accommodate such a cap?


    With ease, do it all the time.

    Light Weight, Good Fit

      I have trained and raced in the Ionos helmet since May of 08, and continue to use it. The Giro Ionos helmet is one of the coolest best fitting helmets I have worn. The 21 vents have really come in handy in the heat of summer when you wish you had a fan on your face. The padding inside, X-Static, is precisely placed to provide comfort from the shell and is removable so you can wash the stench out. The adjustment in the back is easy to use, even while riding you can make micro. adjustments easily. Another thing I like is the fact that the helmet weighs in at a mere 309 g, I wear a medium. I use the helmet for the Road as well as on my MTB. Your head is worth the price. Ride On.