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I have heard that the foam protection layer inside the helmet because "hard" over time and its impact absorption properties decrease. So how long does this take or is it urban myth?

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Apparently the air in and around the polystyrene "evaporates". They say you should replace your helmet every 3 years or so. Manufacturers only warranties the helmet for that period aswell.

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I smashed an old helmet last year into pieces, not sure how old the helmet was, would say easy 5 years.


I T-boned a car and landed on my head, it seemed to work perfectly, I'd say probably true but not too serious to worry about.


Just because its only warantied for certain period doesn't mean its useless thereafter(Think about a car for example)

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It's your head you are talking about.


I use bell helmets because of the crash replacement policy, and I do crash, but this lapses after 3 years, and what price is your head worth to you, I'm happy paying R1k every 3 years for this peace of mind.


B) oh well, there's always the Darwin Awards.

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My boet in law is an Engineer and this is one of his favourite fields: Energy transfer


I was discussing the issue with him when I told him I needed to replace my motor bike helmet (also at the advice of 3yrs) and this conversation moved onto cycling helmets. He is a biker but very knowledgeable on the manufacturing process of both helmets.


So he allowed me to first explain my understanding of why 3yrs.


After a pause in the conversation, he busted the myth for me. Its not environmental as we are led to believe, else helmets would only have a use by date like fresh produce (in a motorbike store they will be expose to more carbon monoxide and petrol fumes from the mechanics and workshop). Also the constant bumping of putting down your helmet dose not cause the foam to deteriorate - the energy is easily transferred in this process.


But, he did tell me that after a hard fall, replace without prejudice. He also proceeded to explain that a bicycle helmet is only designed to protect the noggin at 30km/h where my DOT motorbike helmet at 60km/h. He also warned me that the real damage is the unseen damage from these falls - coming of your bike at 20km you might not even see cosmetic marks as the outer plastic is not designed to absorb any energy but the inner foam has cracked. You then continue to use your helmet and the next minor fall, your screwed as there is no longer any protection.


So it all came down to the 3yrs is merely a guideline set by the manufacturers to get us to purchase more helmets. But we are lucky in South Africa and we can pass on our 3yr old helmets to those in need to justify the purchase on a new shell.

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A great resource for researching and understanding bicycle helmets : Bicycle Helmet Safety Institute


On their page on when to replace a helmet, they quote the following statement from MET:


"We are often asked 'For how long is a helmet safe?', or 'how often should I replace my helmet?”' Until now it has been difficult to find any reliable figures to help answer these queries. MET have now developed a series of tests which are conducted on aged helmets to determine a 'best before' date (unless the helmet is involved in an accident. In that case it should be replaced immediately.). The results indicate that, if used properly accordingly to our owner manual, our helmets will still do their job up to eight years after they have been made. Not only is that good news for the customer, it’s great news for the environment!"
(own emphasis)


Pretty interesting to see that one helmet manufacturer is actually trying to measure their helmets' lifespans. Some other good points to consider on that page, it's worth a read.


When I was researching which helmet to buy a few years ago, I found one item interesting on their helmet comparisons page: their concern over the growing popularity of spiky elements on modern helmets (Bell Sweep, for example) and what impact this may have in a crash. Also worth a read.


It is your head after all.





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I'm with cbrunsdon on the phylosophy that use a helmet until you have a hard fall. I'm also in the engineering industry, and some of the mining companies even require you to replace your "Hard Hat" every year. I mean, this is just rediculous, what could possibly happen to a hard hat in a year. It's just marketing to get the regular joe to spend even more money on cycling accessories.

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I'm also in the engineering industry, and some of the mining companies even require you to replace your "Hard Hat" every year. I mean, this is just rediculous, what could possibly happen to a hard hat in a year.

I also spent some time working with companies connected to mineral processing and there're some serious dumbasses working there (to use a kind word). It's probably easier to tell them to replace every year than try and explain the concept of 'if it's stuffed, you should replace it'. Alternatively, said dumbasses are also probably perfectly capable of breaking a hard hat before the year is up...

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