Arai helmet head shape comparison - Photo: Angelica Rubalcaba.

Quantum Signet-larity: Arai’s Round Oval & Long Oval Head Shapes Compared

By Surj Gish, with Fish
Photos by Angelica Rubalcaba

Helmets are such a personal, important part of riding, and yet so many riders get it wrong. We complain of noise, when it’s likely the bike’s screen causing turbulence; about comfort, when we’re probably wearing the wrong size or head shape. We, as in riders, not CityBike staff—we’re smarter than that, eh?

We—CityBike staff this time—get our hands on and our heads into a lot of helmets, partly because we’re moto-journalists and it’s our job (that’s what we tell people), partly because we care deeply about the contents of our nuggets and want to keep the squishy stuff where it belongs—inside our skulls. A few years back, we examined the lifetimes of helmets (“The Truth About Helmets” – November 2014) with the help of the good folks at Bell, who gave us access to their labs, staff, and testing equipment. This time around, we wanted to gain a better understanding of fit, so I emailed my contact at Arai: “Hey, so… can you send us a pair of your latest street helmets, a Quantum-X and Signet-X? We want to write about head shapes and fit and stuff.”

Surprisingly, Arai’s media folks didn’t reply with, “Hey, so… you have any sand? Go pound it.” Instead, they sent us a pair of shimmering, diamond white street helmets, their updated Quantum-X and Signet-X.

Actually, it’s not surprising at all—Arai is one of a handful of real-deal companies in the motorcycle industry, fanatically dedicated to uncompromising safety and comfort in an industry sector where a lot of companies simply update that year’s “collection” with bold new graphics and market that shit as “innovation.”

Max wrote about this after attending the press launch for Arai’s then-new Corsair-X (“Arai: Everything That’s A-right With The Moto Industry” – October 2015) at Thunderhill Raceway, where he briefly shared the track with the Nicky Hayden. Remember how I said we get it wrong a lot? Max was measured and fitted by Mr. Akihito Arai himself, and told he should be wearing a properly fitted medium, not a large. The sport/track Corsair-X is an intermediate oval, by the way, the head shape midway between the round oval Quantum-X and long oval Signet-X that Fish and I compared. Arai says the intermediate oval is the most common head shape.

The Helmets

Arai says the Quantum-X and Signet-X are basically the same helmet other than the fit: “The entire helmet has to be redesigned in order to accommodate for the difference in fit, but they both include the same features like the PB-SCLC shell, the same number of vents, etc.”

PB-SCLC stands for Peripherally Belted – Super Complex Laminate Construction, which uses “multiple materials and techniques created internally by Arai that deliver both performance and affordability.”

It’s clear from the git-go that these are very nice lids—the diamond white paint is subtly gorgeous. Venting is extensive, with an intake under the shield, two in the shield, and two above the eyeport, and six exhausts in the rear. The airflow provided is exceptional. Fish called it fantastic: “I’ve never worn a helmet that flowed air in such an effective yet unobtrusive way.”

The diamond white X-helmets are priced at $699.95, although plain white and pearl black are $20 cheaper, with high-vis yellow listing at $709.95 and graphics going for $

829.95. Both helmets employ Arai’s Variable Axis System, which provides positive, smooth shield action and makes swapping shields super-easy—previously an area of many complaints, rightfully so. Swapping shields on Arai helmets from a few years back used to be a right proper pain in the ass, or at least what passes for a pain in the ass here in The Privileged West, where we unironically complain about such things with vigor.

Both Fish and I found that the shields in either helmet fog easily even in dry, warm environments, but Arai includes a Pinlock insert—problem solved. Not included with the helmet, but available for $89.25, is Arai’s Pro Shade system—a separate shield with a flip-down sunshade mounted on the outside. This system requires a bit of acclimation but works well, shielding the rider’s eyes from bright rays when needed, flipping up and out of the way when not. It’s a unique, slightly-funky solution to a problem that other helmet makers solve with an internal sun shield, a symbol of Arai’s uncompromising commitment to shell design and structure.

We had concerns about potential aerodynamic oddities due to the Pro Shade, but experienced very little. Fish found the helmet’s aerodynamics to be virtually unaffected by the shade’s position; I did hear a bit of whistling in the up position on one bike—likely the result of the airflow dynamics of the bike’s windshield interacting with the shade, as I didn’t hear it on other bikes.

A removable anti-microbial liner lets you wash the interior of your helmet when you notice that not-so-fresh feeling, and there’s a water-repellent chin cover that Arai says smooths airflow, increases the amount of air pulled from the mouth area, and reduces wind noise. That all sounds pretty good, and Fish says it works—I pulled mine off to give my beard room to fly its freak flag.

Long Vs. Round

So yeah, these are super-sweet helmets, reflective of Arai’s top-notch reputation. But we’re here to talk head shapes. Arai told us there are three general types of head shapes: intermediate, long, and round ovals: “The intermediate ovals are slightly longer front to back than they are side to side, where the long ovals are considerably longer front to back, and the round ovals are more proportionate front to back and side to side.” Arai also pointed out that they’re the only company making helmets for all three of these head shapes, because, “Proper fitment isn’t just a matter of comfort: it’s a matter of offering the best protection to the wearer, because a helmet that doesn’t fit properly can’t protect properly.”

Arai helmet head shapes explained.

Here’s more on the three head shapes from Arai’s fit page:

  • Round Oval: used in the Quantum-X model; the most symmetrical shape, but not completely round.
  • Intermediate Oval: used in the most Arai models; middle of the road fit that works for a majority of riders right out of the box.
  • Long Oval: used in the Signet-X; fits long, narrow heads. (Think Xenomorph. Ok, not quite that long.)

Arai helmets offer what the company calls “micro-fitting,” the ability to further customize the helmet’s fit to your unique head shape by peeling away thin layers of foam or using optional thinner or thicker interior padding. Interestingly, Arai also says the round oval Quantum-X can be converted into an intermediate by “simply installing the head liner from a Signet-X or Corsair-X,” which makes us wonder about the veracity of that line about how the “entire helmet has to be redesigned in order to accommodate for the difference in fit.”

Fish and I both wear larges in most helmet brands, but we’ve noticed differences in comfort when swapping lids. Take a look at the photos and you can see why—our heads are obviously shaped differently, so it follows that we’d need different helmets, even if the overall size of our respective nuggets is similar.

We chose helmets for our initial round of testing in a very scientific way—the blind test. But finding and donning helmets while wearing blindfolds proved to be difficult, so I asked Fish to try both on, without telling him which was which. After all, the helmets are visually indistinguishable, at least at first glance.

Fish chose the long oval Signet-X. I would have chosen that one, too, but mostly because the long oval shape offers more room inside for the juvenile grizzly bear attached to my chin. That flawed selection process (“More room for my beard!”) again exposes the problems with how we choose helmets—the round oval Quantum-X turned out to be a more natural-feeling, comfortable fit for me, and presumably will protect my graying gray matter better as a result.

I should tell you that I also regularly wear Arai’s intermediate oval helmets, a Corsair-X and a VX-PRO4, and both fit me well. I’m sure if I was standing trackside with Mr. Akihito Arai, he’d help me understand why I think I’m equally comfortable in an intermediate or round oval, but I’ll save that conversation for the next time I’m trackside with Mr. Akihito Arai.

Fish and I wore our chosen helmets for a few weeks to verify good fit. We then swapped, to see what the other shape felt like—he to the round oval, and me to the long oval. There’s a bit of a flaw in our “science” here, because the helmets have now begun to break in to our respective heads, but it’s still possible to compare the shapes.

Here’s Fish on the differences:

“When we did the blind test, I noticed the long oval’s more uniform pressure on my head immediately. The round oval was simply less comfortable with the strap fastened. Prolonged wear first showed the shape difference with the way the breath guard made contact with my nose while wearing the round oval helmet. The round oval’s chin bar was also uncomfortably close to my mouth. My days spent with the long oval showed it to break in and really fit my head. It simply got more comfortable, and Arai’s quality really showed through, as it got better the longer I wore it.”

Similar to Fish’s front-to-back discomfort with the round oval Quantum-X, the way the long oval Signet-X fit the top left and right sides of my head was troubling, with significant hot spots developing in short order. Switching back to the round oval was like a deep breath of fresh air, the neutral fit comfortable and reassuring, with no hot spots for hours at a time.

The CityBike Fit System

Thanks to this most recent journey into the CityBike R&D labs, you now have a foolproof way to make sure you get the best head shape for your own noggin. Simply shave your head, take a photo, and compare to the pictures of me and Fish. If your head is shaped like mine, you’re gonna be a round oval, or maybe an intermediate. If your dome looks more like Señor Pescado’s, you’re a long oval. It’s that simple.

No, it’s not. Here’s the real CityBike fit system: go to one of the multitudinous local motorcycle shops in the Bay Area, the one with the best helmet selection near you. Try on a bunch of helmets, maybe even ask some questions. You don’t want it to be too loose at first, because it’ll break in—we generally look for a snug fit off the shelf.

Grab the chin bar and check for excessive vertical and horizontal movement, then grab the back and make sure the helmet can’t roll off when pulled forward.

When you find the one that seems to fit right, wear it while walking around the shop for a while, and make sure it still feels good. Buy that one.

This story originally appeared in our September 2017 issue, which you can read in all its high-res glory here.