Giro Aries Spherical Road Bike Helmet Review

I’ll be honest: I didn’t expect a road bike helmet to change much about how I feel when I ride. I’ve worn a number of helmets over the years, and they all do their job: keep my head intact. So when I clipped into the Giro Aries Spherical for the first time, I assumed it would check the same box. Safe? Sure. Lightweight? Probably. Ventilated? Maybe.

Then I rode 25 miles on the Rio Grande Trail in Colorado’s Roaring Fork Valley with 84-degree heat, blazing sun, and zero breeze. A few days later, I hit the Crystal River Trail in nearly the same conditions. That’s when I realized the magic. This helmet doesn’t just work; it disappears.

The Aries Spherical is Giro’s top-tier road helmet with features like MIPS Spherical tech and best-in-class ventilation. Bonus: It’s also one of the top-scoring helmets for safety in Virginia Tech’s independent safety ratings. But beyond the specs, what impressed me most was how effortlessly this thing managed airflow and sweat while I cooked beneath the midday sun.

In short: The Giro Aries Spherical ($350) is one of the lightest, most breathable, and protective helmets on the market. It’s expensive, but in return you’ll get a featherweight feel and hot-weather comfort, all while protecting those brains.

See how the Giro Aries Spherical stacks up against the competition in our buyer’s guide to the Best Road Bike Helmets.

Giro Aries Spherical Road Bike Helmet Review

I started biking like I do most things: full send. When I was 23, my dad bought me my first roadie a year after I graduated from college. After my inaugural, 20-mile voyage on the classic Neva Loop outside of Boulder, Colo., I decided I was ready for more.

A few weeks later, I departed on a 3,893-mile, cross-country cycling trip that lasted 4 months. It was definitely a trial by fire, but I walked (biked?) away from that trip with massive quads and a deep love for anything with handlebars.

Since then, I’ve broadened my horizons. I now spend a lot of time on singletrack with my mountain bike, but also enjoy gravel biking and cruising up and down the Roaring Fork Valley on the Rio Grande, a 42-mile paved bike path that winds from Glenwood Springs to Aspen.

For this testing window, I logged a handful of 20-mile rides on the Rio Grande, as well as a couple of gravel rides on forest roads up near the Thompson Divide. (No, the Giro Aries Spherical isn’t technically a gravel helmet, but it still protects your head!) All of my testing experiences were in hot and dry weather with the occasional breeze, as Colorado didn’t see much moisture or even cloud cover this season.

Fit and Function

Right away, I noticed a difference in how the Aries hugged my head. Giro’s Roc Loc 5+ Air fit system isn’t new, but it’s fine-tuned on this helmet. Now, it’s adjustable both vertically and circumferentially. To deal with the standard circumference tweaking, there is a small, dime-sized dial on the back of the helmet.

Compared to the larger BOA dials found on mountain biking helmets, this one is quite dainty. Still, it’s easy enough to grab and tune, even while you’re riding.

What I most appreciated, however, was the vertical adjustment. I’ll focus on this more below in ventilation, but this system also helps with fit because you can adjust the height in the rear cradle to accommodate how you want the Aries to sit on your head. This isn’t something you do on the fly, but it’s not difficult.

You just locate the rear cradle arms (the U-shaped bit of plastic in the back), pull them out of the helmet, and choose a new spacing within the vertical adjustment track. You’ll know you’ve done it right when you hear them click into place. For me, this was helpful to adjust depending on where I wore my hair (ponytail, anyone?). Once I had this set, there weren’t any pinch points or fiddling while I was on the bike.

I have a larger head for a woman, so I typically wear a medium and the Aries was no different. The overall fit is very low-profile, but it’s not restrictive. Because it’s a featherweight — only 9.5 ounces — you don’t really feel it sitting up there. No bobblehead feeling, no neck tightness, nothing. It’s just a quietly protective shell perched on your dome.

Easy, Breezy Ventilation

Even though I live in the Colorado Rockies at an elevation of around 6,200 feet, it’s been a blazing hot summer with minimal wind, zero moisture, and a whole lot of wildfires. I prefer to get my rides in before the day heats up, but that doesn’t always work out. So, some of them have been quite toasty with temps in the mid-80s.

For me, this is sweat-dripping weather, especially when you’re biking on pavement. And yet, the Aries did a great job of keeping me (relatively) cool.

In total, there are 24 large vents spaced around the helmet, including gigantic ones on the front and top of the helmet. The number itself is a bit generous, but it stems from Giro touting their design. The secret is something called the Aura II.

In this case, it’s a trio of thin strips of polycarbonate that run horizontally across the helmet to reinforce the structure. (And to get to 24, you have to count the five spaces between two of the arches.) But, it doesn’t block the vents or airflow so you effectively have a helmet with some delightfully massive holes.

But, there’s more. Remember the vertical adjustment I was raving about earlier? It also helps with airflow. Since you can adjust the height of the helmet with the rear cradle, you can maximize the space between the top of your head and the helmet itself. On paper, this also maximizes the internal air channels, with special attention toward the ones that pull air over the top of your head and out the back.

Good news: It works in real life, too. I don’t race on road bikes so I don’t have much use for an aero helmet. But the Aries works in the same way in that it pulls airflow in through the front inlet and out through the four back outlets. Even at low speed, I could feel a light breeze tickling my hair — and it was all-around glorious on those steamy hot days. Did it eliminate sweat? I wouldn’t go that far. But it definitely helped.

Bonus: The padding on the inside of the helmet boosts comfort but also absorbs sweat, so I never dealt with it trickling into my eyes. Maybe that’s gross, but it was a win for me.

Safety Matters Most

We all wear helmets when we bike to protect our heads. Thankfully, I didn’t crash while wearing the Aries Spherical. That said, it does have some fantastic talking points in this regard.

When it first came out in 2023, this helmet took the top spot for safety in the Virginia Tech independent ratings. Since then, it’s slid down a bit, but it still has a five-star review. Currently, it owns the third spot for road biking helmets (behind the POC Cytal and the P2R A20). Bottom line: The Aries Spherical is a helmet you can trust with your brain.

For starters, the helmet comes with MIPS Spherical, a safety technology unique to Giro. It’s almost like the ball-and-socket in your hips, only Giro does it with the inner and outer sections of the helmet itself. The two layers have the freedom to move independently from each other by a few millimeters. In fact, you can grab the two layers with your hands and move them around to see it for yourself.

This means the Aries Spherical has the same head protection against rotational impact, but Giro didn’t have to worry about the internal design messing with safety. They could go ahead and add the vertical adjustment system without it tampering with the anti-rotational impact technology.

In real-life riding scenarios, you (hopefully) won’t ever need the MIPS Spherical protection. But you will notice it’s there, especially if you reach up to adjust your helmet while pedaling and push on the wrong spot.

Because the two layers move so independently from each other, you have to push on the exact right zones to actually move the helmet instead of adjusting one layer. It’s not difficult, nor is it problematic. But if you aren’t used to using the MIPS Spherical system, you’ll notice it as different the first few times.

I’ve only been using the helmet for a month, so I can’t speak to its long-term durability. But thus far, this featherweight resists small dings and scrapes from everyday wear and tear (like my daughter spiking it into the back of our car). I suspect it’ll be good to go for the long haul.

Room for Improvement

Nothing is perfect, but my gripes with the Giro Aries Spherical helmet are minor. While I find the helmet plenty comfortable, it’s not as plush as some other versions out there with a lot more padding. But it’s also incredibly light, so that’s the tradeoff you have to accept for shaving ounces.

More noticeable, however, is the price. The Aries Spherical clocks in at $350, which is a lot of cash. Yes, you get a lot for that price: a lightweight, sleek helmet with tons of ventilation, comfort, and high safety standards. But it’s certainly a price point that will prevent beginner or even intermediate cyclists from considering it (especially now that Virginia Tech’s second-highest-ranked road biking helmet is the P2R A20 at $55). But for the experienced pedalers looking for performance, style, comfort, and safety, it’s tough to beat.

Final Thoughts

Everything about the Giro Aries Spherical is a flashy brain bucket, from its spherical technology to its vertical rear adjustment. Heck, even the colorful pattern on the version I tested was delightfully snazzy with pinks and pops of turquoise. And that’s what I love about the helmet.

The Aries is unapologetically a road bike helmet that delivers on everything a cyclist could want. It’s lightweight, comfortable, and extremely well-ventilated. The design is sleek and stylish, and it’s one of the safest options out there.

While the cost may price out beginners or intermediates, the Aries Spherical is a great choice for any cyclist — if you can afford it.