A lot of riders don't know that the life of a crash helmet is five years from the date of manufacture, including any shelf life.
At our LSR meetings helmets are looked at by the scrutineering team along with your bike and leathers etc. As well as condition and conformity, Snell or ACU, the date label is checked. Over five years and you don't use it.
A discussion about this often generates a lot of debate from riders who's favourite helmet is in "perfect" condition, never scratched or dropped but maybe ten years old. They are surprised when the deterioration of the expanded polystyrene inner liner is revealed as the reason. Compression from years of wearing the helmet plus hardening from both airborne contaminants and contact with the rider's head means it's no longer going to absorb the shock when your head hits something hard, like the road. Instead of decelerating your head in a way that means you survive your brain smashes into the inside of your skull - meaning you probably won't.
A bit of a pithy topic but well worth the time to read, it may even save your life. A dealer friend of mine is quite hot on this and also dissuades customers from buying cheap helmets. He says "if you've got a cheap head then buy a cheap helmet". Wise words.
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