why the five year life span on helmets?

[Kev m]

So, out of curiosity, I looked up the degradation of expanded polystyrene (styrofoam). The sources stated that polystyrene is chemically inert and so resistant to acids and bases ( so much for the body oil argument. It also went on to mention the environmental problem with its resistant to natural breakdown. That seems to have the ring of truth also.  If polystyrene just fades away, then there wouldn't be such a hue and cry about our overloaded landfills.

So far, science is lining up with the "this is BS " side of the fence.

I don't think what I'm reading from Snell or the helmet manufacturers suggest the lining disintegrates, I'm reading that it HARDENS.

The impact protection is provided by the give in the material. The gradual deformation under load to absorb the impact. If it hardens either through natural aging/atmospheric exposure it would still occupy landfills as well as your old helmet, but in the latter case it might not deform as well, transmitting higher forces to the wearer's head.

And I'm thinking I once read that part of the hardening occurs just from using it. That is, that the very act of wearing it (and it breaking into your head shape a bit) starts to compress the impact absorbing liner.

This also would account for why a helmet tends to loosen up over time.

[Triple Jim]

My guess is that the thin layer of soft foam rubber of the liner is the majority of what compresses over time and makes the helmet feel looser.  It's definitely what disintegrated in my 30 year old Electro helmet, causing rubber powder to get in the wearer's eyes.

[Arizona Wayne]

My guess is that the thin layer of soft foam rubber of the liner is the majority of what compresses over time and makes the helmet feel looser.  It's definitely what disintegrated in my 30 year old Electro helmet, causing rubber powder to get in the wearer's eyes.

That's the part that your body oils, sweat degrade and if you wear something between that and your actual hair/skin like I and others do it will last a lot longer. 

[Kev m]

OK, just to add to the confusion (but in the interest of full disclosure). Here is source (bicycle in origin) that is citing 2 studies (one supposedly Snell testing old motorcycle helmets, and another bicycle helmet test) that tested aged (on the shelf) helmets and saw NO DEGREDATION OF THE ENERGY ABSORING LINERS.

So this seems to be in direct contradiction to what I've been posting from other sources (ironically including SNELL). But it seems to support what Boatdetective has been saying from a materials standpoint.

 

http://www.bhsi.org/replace.htm

Occasionally somebody spreads rumors that sweat and ultraviolet (UV) exposure will cause your helmet to degrade. Sweat will not do that. The standards do not permit manufacturers to make a helmet that degrades from sweat, and the EPS, EPP or EPU foam is remarkably unaffected by salt water. Your helmet will get a terminal case of grunge before it dies of sweat. Sunlight can affect the strength of the shell material, though. Since helmets spend a lot of time in the sun, manufacturers usually put UV inhibitors in the plastic for their shells that control UV degradation. If your helmet is fading or showing small cracks around the vents, the UV inhibitors may be failing, so you probably should replace it. Chances are it has seen an awful lot of sun to have that happen. Otherwise, try another brand next time and let us know what brand faded on you.

At least one shop told a customer that the EPS in his three year old helmet was now "dried out." Other sales people refer to "outgassing" and say that the foam loses gas and impact performance is affected. Still others claim that helmets lose a percentage of their effectiveness each year, with the percentage growing with age. All of that is nothing but marketing hype to sell a replacement helmet before you need it. There is some loss of aromatics in the first hours and days after molding, and helmet designers take account of that for standards testing. But after that the foam stabilizes and does not change for many years, unless the EPS is placed in an oven for some period of time and baked. The interior of your car, for example, will not do that, based on helmets we have seen and at least one lab crash test of a helmet always kept in a car in Virginia over many summers. Helmet shells can be affected by car heat, but not the foam. The Snell Memorial Foundation has tested motorcycle helmets held in storage for more than 20 years and found that they still meet the original standard.

 

Test Lab proof that performance holds up

In 2015 MEA Forensic reported on their extensive testing of used (but not crashed) bicycle helmets shows that the foam liners retain their performance over many years. Some of the helmets were as old as 26 years. They crash tested 675 helmets in their lab. Their analysis showed that there was no significant impact performance change with age. Their data including all 675 helmets tested produced only a 0.7g per year increase in impact readings at the higher drop height. After crash testing the helmets on a standard test rig, MEA took core samples from an uncrashed area of 63 helmets and tested them. This generated data based solely on the foam performance. Again, the findings indicate that helmet liner foam does not deteriorate with age. We have more on this landmark study in this Update newsletter.

[Triple Jim]

Thanks Kev.  It's always nice to read that testing confirms my gut feelings.   

[Kev m]

Thanks Kev.  It's always nice to read that testing confirms my gut feelings.   

 

Hey, just trying to find the facts, whether they agree with what I previously thought or not. lol. 

[oldmxdog61u]

Almost as good as an oil thread!
Having had my share of testing helmet structures over many years of mx racing, including splitting one from impact, my opinion is that a properly fitted new helmet is a wonderful thing compared to a sweated out, liner compressed old faithful. Plus, helmet technology is evolving, and i can say that shots i took later in my career and walked away from i do not think i would have back in the day.  I want the best noggin cushion i can afford, having compressed the hell out of more than my fair share and lived to say "glad i had a good helmet on", without traumatic brain injury.

[Testarossa]

without traumatic brain injury

Whenever I say something similar, my daughter asks "Dad, are you sure?"

[Lcarlson]

<<I'm still using my white 1976 Shoie full face helmet. >>

Notwithstanding the question of materials degradation, Got to figure there have been some improvements in helmet design in 39 years....

[charlie b]

Maybe and maybe not as far as safety goes.

Shell is still fiberglass (unless you have a plastic helmet).

Safety foam is still EPS.

Chin strap, yes.

Visors have improved a little bit as well as the size of the viewport.

I would bet if I still had my old Bell Star it would probably still pass the snell test that it was originally certified with.

But....I love the modular designs, internal sun visors, better venting and better comfort cushions which is why I have a newer helmet.

It isn't really a question of if I want a new helmet, it is, MUST I get a new helmet to be safe?  I think the answer is no. 

[Kev m]

Charlie, honest question as I don't know the answers, but I'd THINK even if the basic materials of the shell and liner are the same, don't you think they may have improved the fabrication techniques?

I'm under the impression helmets have gotten lighter and quieter. I guess I've assumed they've also gotten safer?

[johnr]

I think sometimes we get a little precious about helmets.

I will replace a helmet if I feel I need to because the old one is either a/ damaged, or b/ gotten all lose and sloppy.

I do not believe that an empty helmet falling off a table or a bike will harm it in any significant way.  It is after all designed to protect you from concussion level impacts. (with you in it)

All helmets offer some protection regardless of condition or type. None of them offer anything like the level of protection we would like to think they would. (they also increase the likelihood of walloping your head on the ground in the first place)

A 'use by date' there for is an artifice and is irrelevant.  You are going to want to replace your helmet in any case long before it's effectiveness, such as it is, is seriously compromised.

[JayDee24ca]

<<I'm still using my white 1976 Shoie full face helmet. >>

Notwithstanding the question of materials degradation, Got to figure there have been some improvements in helmet design in 39 years....

Yeah, I suppose. But I also have a first generation Schuberth modular that I paid way too much money for, and it is the noisiest piece of crap I have ever had the misfortune to put on my head. My old Shoei is down right peaceful compared to it. I wear ear plugs whenever I am on a bike.
JD

[rbm]

For some reason a helmet always fits looser after a visit to a psychiatrist.

Ahhh, but how many motorcycles have you see parked outside a psychiatrist's office? Not many, I'm sure.  Motorcycling is the therapy.

[canuguzzi]

Two materials and both receive the same impact. One cracks and deforms somewhat, the other shows no sign of damage.

Which transmitted more energy to whatever was on the other side?

[Lcarlson]

<<Yeah, I suppose. But I also have a first generation Schuberth modular that I paid way too much money for, and it is the noisiest piece of crap I have ever had the misfortune to put on my head. My old Shoei is down right peaceful compared to it. I wear ear plugs whenever I am on a bike.
JD>>

I also had the early gray market Schuberth helmet, and I entirely agree with your assessment. Worst helmet I've ever had. I also wear earplugs on any long or high-speed rides. And no, you don't need to replace your helmet if it whacks the ground without your head in it, at least not according to the Director of the Snell Foundation, who said that was an Urban Legend.

[charlie b]

Charlie, honest question as I don't know the answers, but I'd THINK even if the basic materials of the shell and liner are the same, don't you think they may have improved the fabrication techniques?

I'm under the impression helmets have gotten lighter and quieter. I guess I've assumed they've also gotten safer?

And I assume they are just made to meet the standards, Snell, ECE and/or DOT.  If the materials improved then I would expect them to use less of the material to make the helmets lighter (which has happened in some cases).

Fabrication techniques.  Heck, Arai advertises that they have 15 guys sitting there hand laying the helmet fiberglass.  Can't get more old school than that.  Same way my 1970's helmet was made.

And EPS forming is still done the same way.

So, yeah there are reasons to buy a new helmet, but, I don't think safety is one of them.  Of course, if you are like me and drop your helmet often, then after a while you probably do need to buy a new one :)

[ajwood]

Interesting link on coating a helmet shell with plasti-dip:

https://www.youtube.com/watch?v=o_aingfOl8k

[Triple Jim]

Of course, if you are like me and drop your helmet often, then after a while you probably do need to buy a new one :)

Just do it the way I do... when I drop mine, it always bangs the shield and not the shell.  The shell is spared any damage, but I can hardly see to ride.

[Kev m]

And I assume they are just made to meet the standards, Snell, ECE and/or DOT.  If the materials improved then I would expect them to use less of the material to make the helmets lighter (which has happened in some cases).

Fabrication techniques.  Heck, Arai advertises that they have 15 guys sitting there hand laying the helmet fiberglass.  Can't get more old school than that.  Same way my 1970's helmet was made.

And EPS forming is still done the same way.

So, yeah there are reasons to buy a new helmet, but, I don't think safety is one of them.  Of course, if you are like me and drop your helmet often, then after a while you probably do need to buy a new one :)

Though standards have changed since the 70's, no?

And there is meeting standards, but don't SOME exceed standards?

 

[steven c]

 I still have my mid 70's era Arai which i don't wear and  the foam is much thinner then what you find in a modern helmet.