When riding a motocross, you should always make sure that you wear a reliable safety helmet, but these products are not always effective. Helmets can deteriorate over time for a variety of reasons, including weather and frequent crashes. The right time to replace your helmet depends on how you store it, how often you use it, and the quality of the helmet itself.
Basic components of a helmet
As far as protection is concerned, there are two key components of a helmet. One is the outer shell of the helmet and the other is the liner of the helmet. The shell serves to dissipate impact energy and prevents objects from penetrating the shell to reach the skull. But the more important element is the expanded polystyrene layer of the helmet liner. This layer, known as eps,often made from foam and covered in fabric, the padding can degrade from sweat and hair oils,losing its ability to cushion the head effectively and absorb shocks from collisions or impacts. When your head hits something hard with a lot of force, the energy is absorbed by the eps.
Damage to the outer shell can render the helmet unsafe and therefore unusable. Most helmets are made from fibreglass, carbon fibre, Kevlar, ABS and polycarbonate. Studies have shown that these materials naturally degrade when exposed to UV sunlight for long periods of time. Manufacturers add stabilisers to help reduce this effect, but sunlight will continue to damage the exterior. Examine the helmet shell to see if the colour has faded. Some materials will turn a dull yellow colour, which is a sign that the sun is starting to affect them. You should also look for cracks, breaks, and other signs of structural problems.
It cannot be said that the eps is more important than the enclosure. Both the shell and the eps play an important role, but in most accident situations the eps will absorb most of the energy. Imagine hitting a piece of polystyrene with a hammer. You will compress the material and leave a dent. This is the normal situation for a helmet. This means the eps has done its job. But in the area where the eps is compressed, it will no longer absorb energy efficiently. eps can only be used once. The material does not bounce back. It has no memory. Once an eps is compressed, it cannot be expected to work again. Therefore, if the eps is compressed, the helmet should be replaced.
Some helmets, especially the better quality ones, have a painted eps liner. Usually, the liner is black or grey. The spray paint is there to show if it is deformed. If your skull hits the eps hard enough, the liner will deform and this deformation will cause cracks in the paint. So, if you see cracks in the paint, it's probably time to throw the helmet away.
When should a motocross helmet be replaced?
Like many safety products, motorbike helmets have a recommended shelf life. eps degrade over time. When we ride, we sweat and this moisture is absorbed by the eps. As the eps dries out, it shrinks a little, and when it does, it hardens, making it slightly less effective at absorbing impact energy. It is now believed that eps shrink by 3 to 5 per cent per year if the average annual mileage is 6,000 to 8,000 miles. Therefore, when the eps shrinks to a certain point, it is no longer effective enough to absorb energy. For this reason, helmet manufacturers recommend that helmets should ideally be replaced every five years from the date of manufacture, depending on how often you ride.
Unfortunately, you can't detect if an eps has hardened by just touching it with your finger, as the hardening usually goes deeper into the structure of the eps. Another way to look at this issue is to look at the number of miles expended rather than the time. If a cyclist averages between 6,000 and 8,000 miles per year, it might be advisable to replace the helmet once it has travelled between 40,000 and 50,000 miles.
It's a good idea to store your helmet in a dry, room-temperature place when you're not normally using it. This will help your helmet last as long as possible. Be sure to check your helmet regularly to ensure that all parts are still intact.