Originally Posted by
I-Like-To-Bike
Extract from Snell FAQ:
Why should you replace your helmet every five years?
The five-year replacement recommendation is based on a consensus by both helmet manufacturers and the Snell Foundation. Glues, resins and other materials used in helmet production can affect liner materials. Hair oils, body fluids and cosmetics, as well as normal "wear and tear" all contribute to helmet degradation. Petroleum based products present in cleaners, paints, fuels and other commonly encountered materials may also degrade materials used in many helmets possibly degrading performance. Additionally, experience indicates there will be a noticeable improvement in the protective characteristic of helmets over a five-year period due to advances in materials, designs, production methods and the standards. Thus, the recommendation for five-year helmet replacement is a judgment call stemming from a prudent safety philosophy.
This paragraph reads like it came directly from the marketing department. These theories have no scientific basis at all. If Snell wanted to make their point, they should have taken 1,000 (or more) five year old helmets and conducted the same drop tests as their 2015 models. They probably did but guess what, the results did not warrant buying a new helmet hence no scientific study. As a result, their marketing department was given the job to increase new helmet sales.