How to check your tyres

Safety: only do jobs you are confident with. Never work under a car supported only by a jack, and if a repair affects brakes, steering or suspension and you are unsure, have a garage do it or check your work.

In 2025, 8.4% of car MOT tests failed on tyres. Worn tread and cuts or bulges are the usual reasons. Checking takes five minutes and needs nothing more than a 20p coin, though a proper tread gauge costs about £3.

The legal limit

A car tyre must have at least 1.6mm of tread across the central three-quarters of its width, all the way round. Below that it is an MOT failure and illegal to drive on, with a fine of up to £2,500 and three penalty points per tyre. Stopping distances on a wet road get noticeably longer well before 1.6mm, and many drivers replace tyres at 3mm.

Checking tread depth

1. Park on level ground with the steering straight, then turn it fully to one side so you can see the front tyres’ full width.
2. The 20p test: put a 20p coin into the main grooves. If you can see the outer band of the coin, the tread is close to or below the legal limit.
3. The tread-wear bars: small raised blocks across the bottom of the main grooves. When the tread is level with them, it is at 1.6mm.
4. Check at three points across the width (inside, middle, outside) and at several places round the tyre. Roll the car forward half a turn to check the part that was on the ground.

What uneven wear tells you

• Worn on the inner or outer edge only: wheel alignment is out, often after hitting a kerb or pothole, or a worn suspension part. An alignment check costs around £30–£60 and saves tyres.
• Worn on both edges: the tyre has been run under-inflated.
• Worn in the centre: it has been run over-inflated.
• Patchy or scalloped wear: worn shock absorbers or an out-of-balance wheel.

The inner edge is the one people miss, because you can’t see it without turning the wheel or getting down low. It is a common MOT surprise.

Checking for damage

Run your eyes and hand (carefully) round both sidewalls and the tread. These fail the MOT:

• A bulge or lump in the sidewall. This means the internal structure is damaged and the tyre can fail suddenly. Replace it straight away.
• A cut deep enough to expose the cords, or longer than 25mm.
• Exposed cords anywhere on the tread.
• Objects embedded in the tread that have gone through, such as screws. A screw in the central tread can often be repaired for £15–£25; one near the sidewall cannot.

Fine cracking on the sidewall of an old tyre is not an immediate failure, but it is a sign of age. Tyres more than about six to ten years old are worth replacing whatever the tread depth. The age is the four-digit code on the sidewall: “2319” means week 23 of 2019.

Setting tyre pressures

1. Find the correct pressures on the sticker inside the driver’s door frame, inside the fuel flap, or in the handbook. There are usually two figures, normal and fully loaded.
2. Check when the tyres are cold: before driving, or after the car has stood for a couple of hours. Warm tyres read high.
3. Unscrew the valve cap, press the gauge firmly onto the valve, and read it.
4. Add air at a garage airline or with a 12-volt compressor, checking as you go. To let air out, press the pin in the centre of the valve.
5. Refit the valve caps; they keep dirt out of the valve.

Check pressures monthly and before long journeys. If your car has a tyre-pressure warning light that comes on after you’ve set the pressures, the system may need resetting (see the handbook) or a sensor may be faulty. A warning light that stays on is itself an MOT failure on cars first used from 2012.

Other MOT tyre rules

• Tyres on the same axle must be the same size and type (you can’t mix a run-flat with a normal tyre, or radial with cross-ply).
• The spare isn’t checked at the MOT, but it is worth checking anyway.
• A tyre fouling the bodywork or suspension when steering fails.

Which cars fail on tyres most?

From our analysis of every car MOT in 2025, these popular models failed on tyres most often. If you own or are buying one, it is worth checking this area more carefully. Older cars naturally fail more, so the figures partly reflect each model’s age.

See every model in our MOT data by model.

For the rest of the pre-MOT checks, see our MOT preparation checklist.