Take the 2-minute tour ×  I read the answers to "When or how
often should I replace my bike helmet?", but unfortunately none
of the answers there cites any references.  Have there been any
studies quantifying the claim of reduced protection after single
impact, e.g. in terms of increased risk of injury?  It's easy to
see reasons why manufacturers would want you to believe any
impact kills the helmet - it's hard to set limits on potential
damage, and buying a new helmet means additional profit.  Horse
riding helmets come with similar warnings, but my first one
seemed to survive several years while I was learning show
jumping - including way more falls than I could have afforded
new helmets.  share|improve this question add comment  2 Answers
up vote 11 down vote accepted  There is a lot of good
information about this here. One paragraph from the article
outlines the basic idea of this:  Crushing the cell walls
destroys the impact management ability for most stiff foams, so
the helmet has to be replaced after