Even with no hard bangs, you should replace your mountain bike helmet every three years (on average) to ensure that the helmet you’re currently wearing is best able to do what it was designed to do – protect your brain from injury. Your helmet may look quite fine after three years.
You may never have had a tumble where your helmet took an impact. But mountain bike helmets are made of materials that are intentionally light to ensure comfort while protecting your head. Unlike a pair of hardy Shimano SPD pedals, these materials in modern helmets don’t last forever.
Significant changes in temperature as well as lengthy exposure to UV light can degrade the EPS (expanded polystyrene), which is the core/shell of the modern cycling helmet. Some sunblocks contain substances that can erode EPS and sweat can also gradually wear into your helmet’s EPS and affect its structure. By replacing your mountain bike helmet every three years, you are giving yourself both peace of mind as well as optimal protection.