Why Tyre Age Matters as Much as Tread Depth

Most drivers judge whether a tyre needs replacing by looking at the tread to see if there's still plenty of rubber left, it must still be good. But tyres don't just wear out from driving on them. They also age; and a tyre with plenty of tread left can still be unsafe if it's simply old.

Rubber degrades even when it's not being used

Tyre rubber is a mix of natural and synthetic compounds that slowly harden and lose flexibility over time, through exposure to heat, UV light and simple ageing (a process called oxidation).

This happens whether the tyre is being driven on daily or sitting in a shed barely used, which is why a spare tyre or a tyre on a car that's rarely driven can still be a safety risk even with tread depth to spare.

How to find out how old a tyre actually is

Every tyre has a four digit code stamped into an oval on the sidewall, usually ending in "DOT" followed by a string of characters. The last four digits are the ones that matter: the first two are the week of manufacture, and the last two are the year (How to read a tyre sidewall). So a code ending in 2321 means the tyre was made in week 23 of 2021. It's worth checking this on all four tyres, plus the spare tyres don't always get replaced as a full set, so it's common for one or two to be considerably older than the others. 

The general rule of thumb

Most tyre manufacturers recommend replacing tyres once they reach around 6 to 10 years old, regardless of remaining tread, and inspecting them more closely from the 5-year mark onward. Warning signs of age related deterioration include fine cracks in the sidewall rubber (sometimes called weather cracking), a slightly discoloured or faded appearance, and a harder, less pliable feel to the rubber compared to a newer tyre.

Why this matters more than people assume

An aged tyre is more prone to sudden failure including on the highway, at speed, in hot weather, which is exactly when the consequences are worst. Because the tyre can still look fine and hold air normally right up until it fails, age related degradation is one of the easier safety issues to miss without actually checking the manufacture date.

Next time you're in for a service, ask us to check the manufacture date on all four tyres and the spare. It takes a minute and it's the kind of thing that's easy to overlook.

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