Why are bicycle helmets so flimsy?

April 25, 2006 12:15 PM

I got a new helmet about 4 months ago, and paid about $100. I wear it all the time, and value the safety it provides. However, I've noticed that nearly all bicycle helmets only have the harder plastic part on the OUTSIDE of the helmet, not also in the inside. I find my helmets always get dented on the inside or on the areas where there is no plastic covering. Why can't they manufacture ones that have it all around the foam areas? or at least on the surfaces that have contact with the table if I put it down on a table? Very frustrating to be always buying a new one, just because the foam gets damaged so easily. I'm willing to spend money to protect my brain, but it seems a little plastic would go a long way to make the helmet last a little longer. I know the helmet is supposed to absorb impact, but would it not absorb impact if there was plastic all around the inside and outside?
posted by jldindc to Sports, Hobbies, & Recreation (21 answers total)

If it were hard on the inside it would defeat the purpose. The foam is crushable because when the time comes that your head hits something, part of the energy of the impact will be used up crushing the foam, instead of crushing your skull.
posted by Steven C. Den Beste at 12:24 PM on April 25, 2006

The real purpose of the plastic on the outside of the helmet is so that it is slippery enough to slide on concrete, and you're less likely to snap your neck in a crash.

Also, the plastic cracks quite easily. You could get some nasty cuts if you had it against your scalp.
posted by teg at 12:26 PM on April 25, 2006

Why are you throwing out your helmets, because there are little dents on the foam on the inside? You shouldn't be. They stand up fine to normal bumps and drops and the like. Unless the helmet takes serious damage (I suppose one could be crushed by a pile of heavy textbooks or something), there's no significant difference between a mint-condition helmet and one with a slightly-dinged-interior.
posted by Plutor at 12:43 PM on April 25, 2006

Other than age or major impact, there's no reason to replace a helmet because of a couple of leetle scuffs or dings. Motorcycle helmets should be replaced if (say) they fall off your seat or tank onto concrete, or once they're older than 3 years, because the foam outgasses and becomes less pliant. I imagine similar is true for bicycle helmets, though since they weigh less it'd be less of a concern about dropping them on the ground.
posted by 5MeoCMP at 1:08 PM on April 25, 2006

jldindc posted "I got a new helmet about 4 months ago [...] I wear it all the time when I ride my bike, and value the safety it provides"

Watch the wording - sounds like you wear it 24/7, riding the bike or not. Could lead someone like me to make a joke at your expense.

Personally, I hang my helmet from the handlebars or set it on a table. Often put it upside down and use it to hold my biking gloves and assorted accessories. Doesn't hurt the helmet any, except for perhaps some small dings and dents here and there, but it's a cosmetic thing. Helmet is fine, either way. Don't sweat it. Nobody except you will really notice or even care much. Unless you're slamming it down on a pile of gravel, nothing you do to it during normal use should really hurt it as much as you make it sound.

If it really bothers you, I don't know what to tell you. You should most definitely NOT try to coat the foam with anything, as it could lead to weakening the helmet and reducing it's brain-protecting qualities. You bonk and get seriously injured when wearing a modified helmet, and your chance of suing the manufacturer for faulty equipment is zero.
posted by caution live frogs at 1:14 PM on April 25, 2006

Have you ever worn Tupperware on your head? If so, you'll know how a bike helmet would feel if there were hard plastic on the inside as well. Think of the foam inside as the crumple zone, like the 5mph bumper on cars - as Steven C. Den Beste said.

Bicycle helmets should be replaced every couple years, unless:

1. You live in a year-round hot climate
2. You are a heavy-sweating person, in which case they should probably be replaced annually.
3. You drop the helmet repeatedly

in which case helmets should be replaced annually. There's really no reason to replace it for a little scratch in the foam caused by setting it on a table.

Somewhat off topic, somewhat on: it's useful to know that every bicycle helmet sold, whether it costs $30 or $300, conforms to the same federal safety standards, so if you do end up buying a helmet annually it doesn't have to cost a fortune.
posted by pdb at 1:17 PM on April 25, 2006

Anyone ever fall of their bike and hit their head? I've fallen off my bike dozens of times as well as been hit by a car and have yet to hit my head. It's always a knee, hand, elbow or shoulder that gets the damage.
posted by any major dude at 2:36 PM on April 25, 2006

any major dude: I didn't exactly fall off my bike and hit my head - I hit my head, then fell off the bike. But yes, I stopped myself with my head (the telephone pole was in the way...) and would be dead or severely disabled if it hadn't been for the Bell Biker (...I'm dating myself here...) helmet I had just started wearing 2 months prior. As it was, I got off with compressed cervical vertebra and concussion that kept me in bed for almost a week.
Helmets save lives, don't doubt it for a minute.
posted by dbmcd at 2:44 PM on April 25, 2006

I'm not doubting that helmets save lives but it's been my experience that once a person knows they are going down arms and legs instinctively cushion the fall to protect the head. I'm just curious how many people reading this have fallen to the ground and hit their head since I haven't.
posted by any major dude at 3:17 PM on April 25, 2006

any major dude: I have fallen off my bike, broken my arm, and subsequently (since my broken arm, for some odd reason, couldn't stand the stress of my body weight pressing down on it) hit my head. True, the extremities take the brunt of most "routine" falls (like not clipping out in time for a sudden stop), but I've known enough people that have had head meet street to make me want to wear a helmet even on the two block ride from my house to the quickie mart.
posted by pdb at 3:17 PM on April 25, 2006

I don't think major dude was advocating not wearing a helmet just offering an observation which I have made myself. I ride pretty often but haven't come off my bike in close to twenty years but I had some hairy crashes when I was younger. I lost lots of skin but otherwise only cracked a collar bone once. I always wear a helmet these days but never once have I hit my head (it only takes once).

This question caused me to take a look at my two year old Bell Fusion. There is no plastic inside the helmet but the edge around the opening is covered by plastic. There isn't a nick or dent inside. I've never taken special care to avoid abusing it. Maybe you need to reassess how you are handling the helmet.
posted by Carbolic at 4:08 PM on April 25, 2006

I know I've had my life saved by a helmet. Maybe not saved from sure death, but definitely saved from a lifetime as a freakin' vegetable. Which is, IMO, nearly infinitely worse.
posted by five fresh fish at 4:51 PM on April 25, 2006

any major dude, A little over one month ago, I had a serious crash at Bootleg Canyon.
I was wearing a full-face TLD D2 Carbon. After about a 6 foot free-fall, I landed on my head so hard, that the carbon shell cracked, and the foam was compressed internally.

I was able to limp away from this crash with no head injuries, and gladly paid for a crash replacement helmet when I got home.
posted by whoda at 6:52 PM on April 25, 2006

I witnessed an accident where someone fell and hit his head. He wasn't wearing a helmet. He started moaning and went into convulsions.
posted by dirigibleman at 7:40 PM on April 25, 2006

Keith Alexander hit his head, without a helmet, last summer. He was buried 2 days later.

It happens, wear the helmet, replace it as needed.
posted by SuzySmith at 9:29 PM on April 25, 2006

I got a new helmet...I wear it all the time, and value the safety it provides.

The protection provided by cycle helmets is extremely limited. The design limits for most helmets can be exceeded with a simple fall onto hard ground from a standing position.

The evidence that cycle helmets actually reduce injuries overall is shaky at best. Some large-scale epidemiological studies actually suggest that they make things worse. Please don't think that wearing a cycle helmet wll make you safe: What makes you safe is riding style and awareness of what's going on around you. Avoiding an accident is always better than being in one, regardless of what safety equipment you use.

What will make you less safe is believing that wearing a helmet makes you safer than you really are.

Keith Alexander hit his head, without a helmet, last summer. He was buried 2 days later.

It's practically impossible to second guess what would have happened in any individual accident had the circumstances been difference: that said ISTR that Keith Alexander hit a concrete pillar head on at speed whilst trying to avoid a child who jumped into his path. Had he been wearing a helmet, this impact would probably have exceeded its design limits. Sometimes you're just unlucky :(

Personally I'd wear a helmet wherever there was a good chance of low-speed falls: off-road stuff, bmx-style riding etc etc. Out on the streets mixing with traffic, the evidence says that helmets don't make a measurable difference. Wear one if you like, but please don't think it makes you any safer.

Re: helmet replacement. There was an in depth article on cycle helmet design and manufacture in a recent edition of Cycle, the magazine of the British Cycle Touring Club, in which the author (an authority on these matters) said that unless a helmet has been damaged in some way there was no need to replace it — the foam doesn't age in a way that affects its performance. Of course, if you leave it out in sunlight, or drop it onto concrete then it should be replaced. I can track down my copy of the article if anyone's interested.
posted by pharm at 5:14 AM on April 26, 2006

Response by poster: Interesting comments everyone. Funny, as we were all commenting, I took another look at my helmet last night, and noticed a hairline crack in the front, right through the main area that holds the foam together. It's not large, but I'll replace it now since the integrity seems compromised. It's strange this crack should even appear, since I've not fallen on this helmet, fallen while wearing it, or whatever. The only thing I've done is put it in my messenger bag when I get off the bike and into the train, coffee shop, etc. And with just that kind of use, it's already cracked. Sounds like the Bell Metropolis is possibly what I'll purchase, or else a more durable "harder" shell helmet, as those used by freeriders or skateboarders. Why is the exterior shell on helmets as thin as it is?
posted by jldindc at 6:02 AM on April 26, 2006

My helmet(s) have only saved me from low-hanging branches. I'm a mountain biker. I am currently wearing a child's helmet, because that was the one that fit best at Walmart. They last forever, I basically replaced the last one because it was geeky looking. I can't imagine paying $100 for a helmet.
posted by JamesMessick at 8:27 AM on April 26, 2006

pharm: sources for the idea that bike helmets don't help on the streets? I'd be interested in seeing that. thanks!
posted by drewbeck at 11:25 AM on April 26, 2006

pharm: sources for the idea that bike helmets don't help on the streets? I'd be interested in seeing that. thanks!

The inestimable Guy Chapman (who I first came across on uk.rec.cycling) has an excellent list of references on the subject of cycle helmets and injury prevention. See cyclehelmets.org for the rundown, as well as his personal site on the topic.

Professor John Adams has done a lot of work on risk compensation and road safety.

Perhaps I should do an FPP on risk compensation. It's an interesting subject.
posted by pharm at 8:20 AM on April 27, 2006

whom I first came across. argle.
posted by pharm at 9:05 AM on April 27, 2006