Originally Posted by
prathmann
There was a study published in the Journal of Biomech. Engr. that gathered almost 700 old worn helmets up to 26 years old (but not previously crashed) and subjected them to the standard certification crush tests used for new helmets. All but two passed and the conclusion was that there is only very minimal deterioration over time.
The five year thing is a lawyer thing, not an engineering thing.
The companies figure that after 5 years you have abused it, even if unintentionally, enough to potentially compromise it.
So they are washing their hands of liability by putting a 5 year "life" on them.