How to Check Your Tyres: Tread Depth, Pressure and Age

Tread depth: the legal minimum and what it means in practice

For cars, the legal minimum tread depth in Great Britain is 1.6mm across the central three-quarters of the tyre's width, and around its whole circumference. Vans and some other vehicle types have different requirements, so check the current rules for yours.

Treat 1.6mm as the line you must never cross, not as a target. A worn tyre clears water much less effectively, so wet braking distances stretch out well before the tread reaches the legal limit. Many drivers choose to replace tyres comfortably before they get that low, particularly ahead of winter.

The 20p test, and why it is only a rough guide

Slot a 20p coin into the main grooves. If the dark outer band of the coin is hidden by the tread, the groove is probably deeper than the minimum. If you can see the whole band, the tyre is at or near the limit and needs looking at.

The caveat is that a coin is a quick screen, not a measurement. It will not tell you whether you are at 1.6mm or a little above, and it only checks the spot you push it into. Wear is often uneven, so test several places across the tyre and on all four, and use a proper gauge if you want a real number.

• Check the inner, middle and outer parts of each tyre
• Look at all four tyres, not just the front pair
• Run your hand around the tread to feel for steps or feathering
• If the coin test is borderline, get a tread gauge reading or ask a garage to measure it

Pressure: the check people forget

Correct pressures for your car are in the handbook and usually on a sticker in the door frame or fuel flap. There is often one figure for normal use and another for a fully loaded car, so read the label properly.

Check pressures when the tyres are cold, ideally before a journey, because driving warms the air and raises the reading. A tyre that is under-inflated overheats, wears on both shoulders and increases fuel use. One that is over-inflated wears down the centre and gives a harsher ride. Remember to look at the spare if you carry one.

Reading the age of a tyre

On the sidewall you will find a code beginning with the letters DOT. The last four digits are the date of manufacture: the first two are the week and the last two are the year, so 2619 would mean the twenty-sixth week of 2019.

Rubber hardens and cracks with age, even when a tyre has barely been used. Cars that sit on a drive for long periods, caravans and spare wheels are the usual culprits. There is no single age at which every tyre must be scrapped, but if your tyres are getting old, or show fine cracking in the grooves or sidewall, have them looked at rather than guessing.

Sidewall damage, bulges and what to do

Run a torch around both sidewalls and the inner edges you cannot easily see. You are looking for bulges, bubbles, cuts, cracks, exposed cord or nails and stones lodged in the tread.

A bulge in the sidewall means the internal structure has been damaged, often by a pothole or kerb strike, and the tyre can fail without warning. Do not drive on it. Fit the spare or call for recovery and have the tyre replaced. If a nail or screw is in the tread, do not pull it out at the roadside, as the tyre may deflate quickly. Get it checked, as a puncture repair may be possible depending on where the damage is.

Frequently asked questions