This is how often you need to buy a new motorbike helmet

BERLIN: Most helmets might feel like they're built for a lifetime, but soon enough comes the time when a new one is necessary, even if the old one still looks good.

Motorcyclists should always buy a new helmet after about five to seven years, according to the experts at Germany's IFZ institute for motorcycle safety.

Bicycle safety experts also suggest roughly the same time frame of around 5 years for cycling helmets - even sooner if it's been banged around lots or been in a crash.

Even well-maintained, crash-free motorbike and bike helmets that look as good as new can still pose a safety risk if they have simply become too old.

No matter how much the helmet is used, the material will start to wear in a way that you won't see from the outside. In the event of a crash, they may no longer provide sufficient protection.

So-called thermoplastic motorbike helmets should be replaced a little earlier, while thermoset helmets can last a little longer than five to seven years.

This is because even the outer shell of thermoset helmets, which is better protected against ageing, loses some of the damping quality of the inner shell. If in doubt, you're usually better off following the manufacturer's instructions.