How long do helmets last?

Are there any materials scientists on the board? Here's a question that comes to my mind every now and then: what is the useful life of a helmet if you don't crash? They are mostly made of foam, after all, and their usefulness during an impact must be related to the shock absorption capacity of the foam. I assume that foam degrades over time, becoming stiffer, so perhaps it might be better to replace the helmet every couple of years. Since this is way out of my expertise, I have a tough time doing a good search of research papers.

Edited to add: The Bicycle Helmet Safety Institute recommends replacing the helmet every 5 years; Bell recommends every three years. There does not seem to be much testing out there. Here's the link: http://www.helmets.org/replace.htm

I have no expertise, but that rarely stops me from offering an opinion. :p:cool:

Not only BHSI, but Snell also, still have the 5-year rule on their websites, which has been in place for decades.

I've read some speculation that the newer, lighter, more ventilated bicycle helmets - which have much more surface area per volume of EPS than older helmets used to when the standards organizations came up with that 5-year recommendation - are consequently less durable. The idea makes sense to me.

I've also noticed that my current helmet, which is about 3-1/2 years old, is looking pretty beat up around the edges, even though I'm careful to take good care of it. It's never been crashed, may have been dropped from handlebar height once or at absolute most twice, it's stored in a ventilated bag when it's not being worn so that it dries quickly. When I transport it, it lives in the bag on top of my shoes, and the only things I put inside/on top of it are plastic sunglasses, HRM strap and, in season, a knit cap. And gloves, when I park the bike for a rest break, but not when it's being stored (so the gloves dry separately from the helmet). I can't say it's never been in a hot car, but I don't make a habit of that. Maybe a total of 20 hours in the lifetime of the helmet, never more than three hours at a time, and those are both high estimates. So it's truly "normal wear and tear," but the EPS is visibly deteriorated.

I haven't been in a huge panicked rush to replace it, but maybe I should be. I'm definitely going to replace it within the next three to four months.

Yes, I have heard the 5 year deal too. But I agree, it depends on how it looks.

If you are in the market for a new one, perhaps these new Rudy Project ones will come down in price. The Rudy Project Sterling comes in highly fluorescent colors:

http://www.e-rudy.com/index_inner_de...id=HL512101MUS

(page down and you will see the other colors)

But the price is off the wall. I have never spent more than $50 on a helmet. But those are soooo pretty!

There's an ad in last month's LAB magazine that gives members a hefty discount on Rudy Project helmets. If you're in the USA and considering one of those anyway, it's a great reason to join LAB and support bicycle-friendly transportation infrastructure.

I'm torn between ordering one of those vs. supporting my LBS.

I said before that I wasn't going to spend a lot of money on my next helmet. I estimate about a 20% difference in comfort between my $180 Giro Pneumo and the $40 Serfas I wore before that. But now that it comes time, the siren song of more expensive must be better, and a really expensive helmet at a 40% discount must be best of all. I'm such a sucker. :rolleyes:

I just replaced my Bell helmet after about 3-1/2 years. However, my reasoning really had nothing to do with safety, but rather two other factors:

1 - that old helmet stinks to high heaven and no matter what I do, it still stinks.

2 - the old helmet's chin straps, although I've cleaned them, must be harboring some horrible pimple germs because they are making my jawline and under my chin break out.

Now that I've replaced the thing, I'm glad to read that maybe I should've been replacing it for safety's sake as well!

Helmets are made from extruded polystyrene (EPS), a rigid foamed polymer. EPS is an extremely durable polymer... the same thing they make foam coffee cups from. It does not biodegrade (break down in the environment from exposure to oxygen, ozone, etc.) nor does it photodegrade (break down from exposure to sunlight). It might dissolve if you poured some sort of petroleum solvent or mineral spirit on it, it might melt if you heat it to more than 185 degrees F (85 degrees C), and it will burn if you put it in a fire.

A demonstration that I use in some of my League classes is to take a styrofoam coffee cup (also made of EPS) and talk about how durable it is in the environment (my real job is working for the state EPA). You can take this cup, throw it away, it goes into a landfill. 500 years from now, you could dig up that same cup, wash it & sanitize it, and it would be nearly as good as new. EPS is that durable (or persistent, depending on your view).

Next, I hold the cup up, and crush it in my hand. The plastic is still there, just as good as ever, but as far as putting coffee or any other liquid in that cup, it's just "used up" and unsuitable for that purpose. The same thing goes for your helmet if you crash it. The plastic may look okay, and you might be able to pull it back into some sort of cup shape, but it sure won't hold your coffee. Neither would your crashed helmet work to hold your brains in... and your brain can't heal itself when you hurt it.

So, there's no chemical reason to discard your helmet simply based on the passage of time. The major reasons I've found for replacement (other than the occasional crash) is that some of the non-EPS components can break or wear out... such as the pads inside, the suspension system, or maybe the plastic coating over the EPS foam may fade or peel away.

Tom

Tom, I always read and understood that it was UV plus the acids and oils from skin and hair that degrade the EPS.

If you've ever done beach or river cleanup, you've found pieces of styrofoam coolers or crab pot markers that have been in the sun for extended periods of time. The bonds between the beads are weakened and the EPS is brittle and crumbly.

You've seen EPS cups degraded by petroleum solvents such as lipstick, or by touching them with greasy, oily or gassy hands in the garage. Those burn right through EPS. I understand that petroleum products don't have the same structure as animal fats, but it's plain that SOME oils can degrade it, and I don't like to take a risk quibbling about WHICH oils. Obviously animal fats WILL degrade EPS when exposed to heat - if you've ever reheated food containing cheese in the microwave, in an EPS restaurant tray. Not that I do that any more or encourage anyone else to do it, but most of us oldsters have probably done it in the past. Again, the EPS will be intact when the contents are water-based only (showing that it's not the heat alone that dissolves the EPS, but heat plus animal fat). Does the heat merely accelerate the animal fat's ability to dissolve EPS - so that it will still happen over years at a helmet's normal temperatures? Or does it actually change the reaction somehow? I'm not willing to take the risk that it's the latter.

Plus, many hair pomades, skin moisturizers, and sunscreens that could come in contact with a helmet, DO contain petroleum solvents.

Acids - maybe you did a science experiment in grade school. I've never forgotten how the lemon extract that one student brought in, literally melted the inside of the plastic measuring cup that our third grade teacher was using. At that age and at that distance of years, I don't know what kind of plastic it was, but it definitely could have been clear polystyrene. Again, obviously a much stronger acid than sweat, but I've read that sweat has a pH of 4 to 4.5, and the exposure is constant and very long term unless you rinse your helmet after every ride (which would still leave the oils).

Not a risk I'm willing to take, is the bottom line. I'm lucky to have a local recycler of EPS (in most places, unfortunately, the carbon cost of transporting it is greater than what's recovered by recycling). Even with that, obviously replacing my helmet often isn't totally carbon neutral, but I'm walking and talking because of a helmet I wore - Tulip and Mel's daughter are alive because of their helmets - I'm not taking the risk.



As far as putting it in the landfill, isn't the same thing true of a peanut butter sandwich on organic whole wheat bread? I wouldn't take lack of decomposition in a landfill as an indication of what might happen to something more exposed.

:eek:True... Over ten years or so, I haven't seen much chemical degradation of the foam in the batches of helmets I've gone through, though it's a wholly different story with the little cushioning pads, straps, etc. I keep my hair trimmed fairly short, and don't use anything but shampoo and water on it. My helmets' risk are way more physical than chemical ;-) Somebody who uses a lot of other stuff on their hair may very likely have a different experience.

I still wind up replacing my helmet about every year and a half or so, simply because the pads wear out or get really ratty, or I find a "prettier" lid. While I went through a number of helmets in in younger and wilder days, I haven't actually crashed one in a little over three years now, other than getting hit by a drunk driver back last February...

And personally, I wouldn't recycle that cup from the landfill... and certainly not the sandwich. Sanitary landfills aren't really that sanitary, nor are they all that leak-proof. Lots of nasty stuff sitting down there against the liner
:eek:

Tom

Quote:

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Originally Posted by OakLeaf

.... I can't say it's never been in a hot car, but I don't make a habit of that. Maybe a total of 20 hours in the lifetime of the helmet, never more than three hours at a time, and those are both high estimates.......

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Ummm, this matters?

:eek:

Quote:

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Originally Posted by Catrin

Ummm, this matters?

:eek:

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Yep. Since it can easily reach into the 100s in a closed car in summer, that probably accelerates the breakdown of the plastic.

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Originally Posted by Owlie

Yep. Since it can easily reach into the 100s in a closed car in summer, that probably accelerates the breakdown of the plastic.

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Uhoh...guess I should consider a new helmet. It looks pretty beat-up anyway :o

I was reading VeloNews (this column) and I found this:

"Nick,
I’ve heard that helmets deteriorate over four or five years, even unused ones. True of false? -Phil
[...]
Helmets do deteriorate over time and especially when exposed to UV. Nic Sims at Specialized told me Specialized destroys any helmets in its warehouse that are four years old or older. So, Phil, you’re better off looking for a new lid."

How long do helmets last?
Depends on how well you ride or how others drive.

Quote:

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Originally Posted by Zen

How long do helmets last?
Depends on how well you ride or how others drive.

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It would be great to go 4 years without smacking my noggin on the tarmac. Did I mention that I always wear a helmet when I ride? (I should probably keep it on just for walking around.)