How good is your helmet? Will it actually protect your brain in your next crash? These seem like easy questions, ones you probably think you can answer by reciting the lofty standards your helmet meets and the lofty price you might have paid for it. But the real answers, as you are about to see, are anything but easy. Is a SNELL rating worth the extra cost to find a helmet with this rating?
There’s a fundamental debate raging in the motorcycle helmet industry. In a fiberglass-reinforced, expanded-polystyrene nutshell, it’s a debate about how strong and how stiff a helmet should be to provide the best possible protection.
Why the debate?
Because if a helmet is too stiff it can be less able to prevent brain injury in the kinds of crashes you’re most likely to have. And if it’s too soft, it might not protect you in a violent, high-energy crash. What’s just right? Well, that’s why it’s called a debate. If you knew what your head was going to hit and how hard, you could choose the perfect helmet for that crash. But crashes are accidents. So you have to guess. To understand how a helmet protects—or doesn’t protect—your brain, it helps to appreciate just how fragile that organ actually is. The consistency of the human brain is like warm Jello. It’s so gooey that when pathologists remove a brain from a cadaver, they have to use a kind of cheesecloth hammock to hold it together as it comes out of the skull.
Your brain basically floats inside your skull, within a bath of cervical-spinal fluid and a protective cocoon called the dura. But when your skull stops suddenly—as it does when it hits something hard—the brain keeps going, as Sir Isaac Newton predicted. Then it has its own collision with the inside of the skull. If that collision is too severe, the brain can sustain any number of injuries, from shearing of the brain tissue to bleeding in the brain, or between the brain and the dura, or between the dura and the skull. And after your brain is injured, even more damage can occur. When the brain is bashed or injured internally, bleeding and inflammation make it swell. When your brain swells inside the skull, there’s no place for that extra volume to go. So it presses harder against the inside of the skull and tries to squeeze through any opening, bulging out of your eye sockets and oozing down the base of the skull. As it squeezes, more damage is done to some very vital regions.
The parts and anatomy of a motorcycle helmet
To prevent all that ugly stuff from happening, we wear helmets. Modern, fullface helmets, if we have enough brains to protect, that is. A motorcycle helmet has two major parts: the outer shell and the energyabsorbing inner liner. The inner lining is made of expanded polystyrene or EPS, the same stuff used in beer coolers, foam coffee cups, and packing material. Outer shells come in two basic flavors: a resin/fiber composite, such as fiberglass, carbon fiber and Kevlar, or a molded thermoplastic such as ABS or polycarbonate, the same basic stuff used in face shields and F-16 canopies.
The shell is there for a number of reasons. First, it’s supposed to protect against pointy things trying to penetrate the EPS—though that almost never happens in a real accident. Second, the shell protects against abrasion, which is a good thing when you’re sliding into the chicane at Daytona. Third, it gives Troy Lee a nice, smooth surface to paint dragons on. Riders—and helmet marketers—pay a lot of attention to the outer shell and its material. But the part of the helmet that absorbs most of the energy in a crash is actually the inner liner.
When the helmet hits the road or a curb, the outer shell stops instantly. Inside, your head keeps going until it collides with the liner. When this happens, the liner’s job is to bring the head to a gentle stop—if you want your brain to keep working like it does now, that is.
Helmet designers have devised a number of different liner designs to meet the different standards. The Vemar VSR uses stiffer EPS than most, but has channels molded in to soften the assembly (to ECE specs) and enhance cooling. The great thing about EPS is that as it crushes, it absorbs lots of energy at a predictable rate. It doesn’t store energy and rebound like a spring, which would be a bad thing because your head would bounce back up, shaking your brain not just once, but twice. EPS actually absorbs the kinetic energy of your moving head, creating a very small amount of heat as the foam collapses.
The helmet’s shell also absorbs energy as it flexes in the case of a polycarbonate helmet, or flexes, crushes and delaminates in the case of a fiberglass composite helmet. To minimize the G-forces on your soft, gushy brain as it stops, you want to slow your head down over as great a distance as possible. So the perfect helmet would be huge, with 6 inches or mosre of soft, fluffy EPS cradling your precious head like a mint on a pillow. Problem is, nobody wants a 2-foot-wide helmet, though it might come in handly if you were auditioning for a Jack in the Box commercial. So helmet designers have pared down the thickness of the foam, using denser, stiffer EPS to make up the difference. This increases the G-loading on your brain in a crash, of course. And the fine points of how many Gs a helmet transmits to the head, for how long, and in what kind of a crash, are the variables that make the helmet-standard debate so gosh darn fun.
Four types of motorcycle helmet safety standards
The Schuberth S1 uses five separate foam parts glued together to meet the ECE standard. Standardized Standards To make buying a helmet in the U.S as confusing as possible, there are at least four standards a street motorcycle helmet can meet. The price of entry is the DOT standard, called FMVSS 218, that every street helmet sold here is legally required to pass. There is the European standard, called ECE 22-05, accepted by more than 50 countries. There’s the BSI 6658 Type A standard from Britain. And lastly the Snell M2000/M2005 standard, a voluntary, private standard used primarily in the U.S. So every helmet for street use here must meet the DOT standard, and might or might not meet one of the others. Just by looking at the published requirements for each standard, you would guess a DOT-only helmet would be designed to be the softest, with an ECE helmet very close, then a BSI helmet, and then a Snell helmet. Because there are few human volunteers for high-impact helmet testing—and because they would be a little confused after a hard day of 200-G impacts— it’s done on a test rig.
The helmets are dropped, using gravity to accelerate the helmet to a given speed before it smashes onto a test anvil bolted to the floor. By varying the drop height and the weight of the magnesium headform inside the helmet, the energy level of the test can be easily varied and precisely repeated. As the helmet/headform falls it is guided by either a steel track or a pair of steel cables. That guiding system adds friction to slow the fall slightly, so the test technician corrects for this by raising the initial drop height accordingly. The headform has an accelerometer inside that precisely records the force the headform receives, showing how many Gs the headform took as it stopped and for how long.
If you test a bunch of helmets under the same conditions, you can get a good idea of how well each one absorbs a particular hit. And it’s important to understand that as in lap times, golf scores and marriages, a lower number is always better when we’re talking about your head receiving extreme G forces.
What is the SNELL Standard
On the stiff, tough-guy side of this debate is the voluntary Snell M2000/M2005 standard, which dictates each helmet be able to withstand some tough, very high-energy impacts.
The Snell Memorial Foundation is a private, not-for-profit organization dedicated to “research, education, testing and development of helmet safety standards.”
If you think moving quickly over the surface of the planet is fun and you enjoy using your brain, you should be grateful to the Snell Memorial Foundation. The SMF has helped create standards that have raised the bar in head protection in nearly every pursuit in which humans hit their heads: bicycles, horse riding, harness racing, karting, mopeds, skateboards, rollerblades, recreational skiing, ski racing, ATV riding, snowboarding, car racing and, of course, motorcycling.
But as helmet technology has improved and accident research has accumulated, many head-injury experts feel the Snell M2000 and M2005 standards are, to quote Dr. Harry Hurt of Hurt Report fame, “a little bit excessive.”
The killer—the hardest Snell test for a motorcycle helmet to meet—is a two-strike test onto a hemispherical chunk of stainless steel about the size of an orange. The first hit is at an energy of 150 joules, which translates to dropping a 5-kilo weight about 10 feet—an extremely high-energy impact. The next hit, on the The helmets are mounted on a 5-kilo (11 pound) magnesium headform and then dropped from a controlled height onto a variety of test anvils to simulate crash impacts on various surfaces and shapes. In the real world, your helmet actually hits flat pavement more than 85 percent of the time.
All the Snell/DOT helmets we examined use a dual-density foam liner. The upper cap of foam on this Scorpion liner is softer to compensate for the extra stiffness of the spherical upper shell area. Some manufacturers, including Arai and HJC, use a one-piece liner with two different densities molded together. same spot, is set at 110 joules, or about an 8-foot drop. To pass, the helmet is not allowed to transmit more than 300 Gs to the headform in either hit.
Tough tests such as this have driven helmet development over the years. But do they have any practical application on the street, where a hit as hard as the hardest single Snell impact may only happen in 1 percent of actual accidents? And where an impact as severe as the two-drop hemi test happens just short of never?
Dr. Jim Newman, an actual rocket scientist and highly respected head-impact expert—he was once a Snell Foundation director—puts it this way: “If you want to create a realistic helmet standard, you don’t go bashing helmets onto hemispherical steel balls. And you certainly don’t do it twice.
“Over the last 30 years,” continues Newman, “we’ve come to the realization that people falling off motorcycles hardly ever, ever hit their head in the same place twice. So we have helmets that are designed to withstand two hits at the same site. But in doing so, we have severely, severely compromised their ability to take one hit and absorb energy properly.
“The consequence is, when you have one hit at one site in an accident situation, two things happen: One, you don’t fully utilize the energy-absorbing material that’s available. And two, you generate higher G loading on the head than you need to. “What’s happened to Snell over the years is that in order to make what’s perceived as a better helmet, they kept raising the impact energy. What they should have been doing, in my view, is lowering the allowable G force.
“In my opinion, Snell should keep a 10-foot drop [in its testing]. But tell the manufacturers, ‘OK, 300 Gs is not going to cut it anymore. Next year you’re going to have to get down to 250. And the next year, 200. And the year after that, 185.'”
Is SNELL a marketing gimmick?
“The Snell sticker,” continued Newman, “has become a marketing gimmick. By spending 60 cents [paid to the Snell foundation], a manufacturer puts that sticker in his helmet and he can increase the price by $30 or $40. Or even $60 or $100.
“Because there’s this allure, this charisma, this image associated with a Snell sticker that says, ‘Hey, this is a better helmet, and therefore must be worth a whole lot more money.’ And in spite of the very best intentions of everybody at Snell, they did not have the field data [on actual accidents] that we have now [when they devised the standard]. And although that data has been around a long time, they have chosen, at this point, not to take it into consideration.”
Expert opinions on the SNELL Standard
Dr. Hurt sees the Snell standard in pretty much the same light. “What should the [G] limit on helmets be? Just as helmet designs should be rounder, smoother and safer, they should also be softer, softer, softer. Because people are wearing these so-called high-performance helmets and are getting diffused [brain] injuries … well, they’re screwed up for life. Taking 300 Gs is not a safe thing. “We’ve got people that we’ve replicated helmet [impacts] on that took 250, 230 Gs [in their accidents]. And they’ve got a diffuse injury they’re not gonna get rid of. The helmet has a good whack on it, but so what? If they’d had a softer helmet they’d have been better off.” The Z1R ZRP-1 uses a soft, one-piece liner to soak up joule after joule of nasty impact energy. How does the Snell Foundation respond to the criticism of head-injury scientists from all over the world that the Snell standards create helmets too stiff for optimum protection in the great majority of accidents?
“The whole business of testing helmets is based on the assumption that there is a threshold of injury,” says Ed Becker, executive director of the Snell Foundation. “And that impact shocks below that threshold are going to be non-injurious. “We’re going with 300 Gs because we started with 400 Gs back in the early days. And based on [George Snively’s, the founder of the SMF] testing, and information he’d gotten from the British Standards Institute, 400 Gs seemed reasonable back then. He revised it downward over the years, largely because helmet standards were for healthy young men that were driving race cars. But after motorcycling had taken up those same helmets, he figured that not everybody involved in motorcycling was going to be a young man. So he concluded from work that he had done that the threshold of injury was above 400 Gs. But certainly below 600 Gs.
“The basis for the 300 G [limit in the Snell M2000 standard] is that the foundation is conservative. [The directors] have not seen an indication that a [head injury] threshold is below 300 Gs. If and when they do, they’ll certainly take it into account.”
So nobody is being hurt by the added stiffness of a Snell helmet, we asked. “That’s certainly our hope here,” answered Becker. “At this point I’ve got no reason to think anything else.”
The ECE Standard of helmet testing
The Snell Foundation may have no reason to think anything else. But every scientist we spoke to, as well as the government standards agencies of the United States and the 50 countries that accept the ECE 22.05 standard, see things quite differently.
The European Union recently released an extensive helmet study called COST 327, which involved close study of 253 recent motorcycle accidents in Germany, Finland and the U.K. This is how they summarized the state of the helmet art after analyzing the accidents and the damage done to the helmets and the people: “Current designs are too stiff and too resilient, and energy is absorbed efficiently only at values of HIC [Head Injury Criteria: a measure of G force over time] well above those which are survivable.” As we said, it’s a lively debate.
You can also find independent safety ratings for helmet here: https://sharp.dft.gov.uk/
