There is a piece of motorcycle wisdom that often comes as a surprise to riders new and old. Helmets expire. Five years after a helmet was made, whether it saw daily use or lived in your closet, you should assume a helmet is past its prime, and it should be replaced. Manufacturers cite the five-year limit, race and track organizations won’t let moto pilots fly without a fresh lid and instructors wouldn’t hear of handing out old helmets to new riders.
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So why is five years the limit? Which part of a helmet silently and menacingly deteriorates past the point of use, even while it sits on a shelf?
The answers are complicated—part myth, and part fact. But one thing is true. The five-year replacement advisory always comes back to the Snell Memorial Foundation. Asked about the five-year limit, helmet manufacturers tend to point to studies conducted by the respected not-for-profit safety certification outfit, which was established in 1957 by Dr. George Snively after the tragic death of race-car driver William Snell.
DOT might be the official safety designation required in the U.S., but a Snell certification stands as a separate, even more virtuous mark of approval. So it’s only natural that the authoritative organization receives a constant stream of inquiries from riders who wonder why they have to toss out their perfectly shiny-looking helmet because of a date stamp.
The answers, often penned by Snell Executive Director Ed Becker, are eloquent and provide an overview of Dr. Snively’s research. But their conclusions are fairly blunt: “Your twelve-year-old helmet could be as good as the day it was made, but no one here thinks you should be willing to bet your head on it.”
That’s what it comes down to, right? The question of whether you’re willing to risk a brain container that might have gone bad, leaving you unprotected in a crash.
The research that Snell’s five-year maxim is based upon is in itself a bit mythological. Established through two studies conducted by Dr. Snively in the late 1970s, there isn’t much data, only hunches. In his responses to queries, Becker often reports that these studies were “never written up or published.” Even so, few would question the renowned outfit’s good intentions.
The first of these oft-cited unpublished studies was conducted with used helmets donated by officers retiring from the California Highway Patrol (CHP), and the other was an experiment which Dr. Snively conducted by leaving a bunch of brand-new helmets on a garage roof in the Sierras to expose them to the elements over several years. Evaluations of these helmets are what Snell’s five-year replacement advisory are based upon today.
Essentially, Dr. Snively’s tests showed a great inconsistency in the lifespan of helmets. Whether they were of the same make and model, exposed to the same elements on a rooftop over years, or they were the battle-worn helmets of police officers, tests showed that over time some performed flawlessly while others were inadequate. Becker explained that among the CHP helmets, Dr. Snively “found that some as old as 12 years tested as if they had just rolled out of production, while others of the same vintage failed miserably.”
More baffling was the fact that there were no identifiable exterior signs that a helmet had deteriorated. So there was no easy way to say that a helmet was past its prime. From there, Becker described, Dr. Snively “concluded that after five years of use, he could not assure himself or anyone else that a helmet could continue to protect.”
Meanwhile, the rooftop helmets “continued to perform like new, even after several seasons of the elements,” Becker said, leading Dr. Snively to conclude “that it was wear and tear, and not time or exposure to weather that took helmets down.”
So that’s the somewhat mystifying and paradoxical history of the five-year rule, but since those early days of standard-setting, helmet manufacturers have conducted their own research.
“We have to look at helmets as a piece of gear designed to do a very important job, and that job is not to last forever, or take abuse and still deliver performance as designed,” explained Brian Weston, Managing Director of Arai Helmet. “It was designed to get between the rider and the impact, destroying itself in the process so as to reduce as much of the impact energy before it reaches the rider. Even at low speeds, that is a tall order for a mere 1/8” shell and 1-1/2” of foam. And, since helmets don’t have wear bars in the tread to indicate when it’s time to replace it, some measure of when a helmet should be retired and replaced is necessary, and as visual inspection of worn helmets can be very subjective, time seems to be the best rule.”
Having seen helmets buffeted by all manner of care, use and abuse over the 32 years he’s been with Arai, Weston pointed out the various ways in which material deterioration affects helmet safety, noting that plastics and rubber components dry out and lose elasticity, and glues holding trim and liner components dry out and lose their grip. Additionally, all components, including the shell and liner, “simply age over time and can also be adversely affected by chemical exposure, reducing performance as designed.”
Even if Dr. Snively’s rooftop tests seemed to indicate that exposure to the elements was irrelevant to the life of a helmet, the exposure factor remains a cause for concern among manufacturers. “The hard outer shells are very strong, but the softer EPS liner inside a helmet can be damaged if stored improperly or subjected to heat and/or chemicals,” observed Matthias Beier, Marketing Coordinator for SHOEI Safety Helmet Corporation. Safety performance is reduced when, “Over time, the EPS materials can absorb deposits (sweat, oils, carbon from the atmosphere, etc.) into the EPS and become brittle and not crush properly anymore.”
As the liner materials compress and lose resiliency over time from normal use, the helmet gets loose. Which, Arai’s Weston elaborated, affects safety in many ways: “A loose helmet moves around and can be distracting and noisy, and in an impact a loose helmet will not manage impact energy as well as a newer helmet that is properly fit and snug.”
Where you store your helmet matters, too. Think twice about leaving it with your bike in the garage, because as the Snell website warns: “Petroleum-based products present in cleaners, paints, fuels and other commonly encountered materials may also degrade materials used in many helmets.”
All of this science and myth leads to some pretty murky reasoning as to why we need to replace our helmets after five years. But actually, just one look at the latest models of “smart helmets” would indicate that head protection is not immune to the onward march of technology, and older models probably should be retired in favor of newer options. Snell itself advises on its website, “Experience indicates there will be a noticeable improvement in the protective characteristic of helmets over a five-year period, due to advances in materials, designs, production methods and the standards. Thus, the recommendation for five-year helmet replacement is a judgment call stemming from a prudent safety philosophy.”
And that’s a safety philosophy that has withstood the test of time, according to Snell’s Becker. If you want to argue that Dr. Snively’s original tests on helmets made in the 1960s would no longer apply today, he says, “Helmet materials and technology have not changed so greatly that Dr. Snively's conclusions would no longer apply. Still, the five-year replacement recommendation is conservative. Most helmets don't get the sort of use I'd expect customary for CHP-issue headgear. And it is a recommendation, rather than a requirement.”
Would you take that recommendation, or are you willing to bet your head on it?
Kirsten Nelson (@writetoride) is Content Director of The Throttle Stop at BikeMinds. A writer and editor based in New York since 1998, she became fully immersed in motorcycling while briefly living in Utah, where adventure, sport and touring rides are a part of daily life. There she also became obsessed with MotoGP racing, and so it happened that when she moved back to Brooklyn, she added moto journalism to her 17-year career in technology and culture writing. Now she's finally taking her motorcycle knowledge to the streets as a rider in training in NYC.
Header Image courtesy of Arai.
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