Why change every 5 years?

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The full question is if you buy a premium helmet from one of the top manufacturers, why they only guarantee your helmet for 3 to maximum 5-years.

The truth is that you not even should trust the maximum safety of any international motorcycle helmet manufacturer specs in Thailand.

UV-light has a devastation effect over time on all man-made materials, even carbon fiber what is many times stronger than steel will in time turn useless by ultra-UV radiation.

You cannot hide from UV-radiation, so all things man made have an expired date. (even frames of very expensive motorcycles).

But UV-radiation and helmets are basically a direct contact object, and as UV-radiation is in Thailand 30% higher than in Europe.

I would scale down the real safety of a motorcycle helmet tested in Europe from 5-years back to 3-years in Thailsnd

In the movie TT3D Closer to the edge. When asked about superstition John McGuinness, the current lap record holder, said that he always wears the same helmet at the TT.

So I think even the 5 years is a bit conservative. If you keep the helmet in a bag in a cupboard when not riding, change it when the strap breaks or the inside gets too ratty for your liking.

The reduction in guarantee has more to do with lawyers than reality.

On the flip-side if you commute everyday here and get all hot and sweaty twice a day, a 3 year-old helmet will acquire enough culture to be eligible for classification by Unesco.