Tyre faults that will fail an MOT

The short answer: tread below 1.6mm in the measured band is an automatic failure, but so are cuts, bulges, exposed cords, mismatched tyres across an axle and a badly seated tyre. Most are visible in a five-minute check.

What the tester checks

• Tread depth — at least 1.6mm across the central three-quarters of the tread, around the whole circumference. Measured at several points.
• Cuts and damage — any cut longer than 25mm or 10% of the section width, deep enough to reach the cords.
• Bulges, lumps or tears. Automatic failure. The casing has already failed.
• Exposed cords or ply anywhere.
• Tyre type mixing — radial and cross-ply mixed incorrectly, or different structures across an axle.
• Correct fitment — right size and load/speed rating for the vehicle, and directional tyres fitted the right way round.
• Seating on the rim, and whether the tyre fouls any part of the vehicle.
• Valve condition — damaged or badly leaning valves.
• TPMS on vehicles first used from 2012, where a fault is a failure.

The ones people miss

Inner edge wear. Easily the most common surprise. You cannot see the inside shoulder without turning the wheels to full lock. Cars fail on inner edges that looked perfect from the outside.

The spare. Not tested on a normal MOT, but worth checking while you are down there.

Directional tyres fitted backwards. Look for the rotation arrow. It happens more often than it should.

TPMS warning light. On a 2012-or-later car, a lit TPMS warning is a failure in its own right. See what the light means.

A five-minute pre-MOT check

1. Turn the steering to full lock and look at the inner shoulder of both front tyres.
2. Check tread in three places across each tyre — inner, middle, outer — using a gauge or a 20p.
3. Run your hand around each sidewall feeling for bulges. Do it with the car stationary and cold.
4. Check the valve caps are on and the valves are not perished or leaning.
5. Roll the car forward half a turn and repeat the tread check — wear is not always even around the circumference.
6. Start the engine and confirm no TPMS light stays on.

If you find a problem

Getting it fixed before the test is cheaper than a retest, and we can come to you rather than you driving somewhere on a tyre you already know is marginal. Call 07989 606060.

Related: tread depth and the law.