What is the most common reason a car fails its MOT?

Lights and electrics fail more MOTs than anything else, at 9.9% of tests. Suspension (7.9%), brakes (5.9%) and tyres (5.5%) come next. Many of these fails are bulbs, wipers and tyres you can check at home.

How much tread do tyres need to pass an MOT?

The legal minimum is 1.6mm, measured across the central three-quarters of the tyre's tread. Tyres worn close to that limit are one of the most common MOT advisories, so check them regularly.

What happens if my car fails its MOT?

A fail means a major or dangerous defect was found. A dangerous defect means the car must not be driven. Driving without a valid MOT risks a fine of up to £1,000, unless you're heading to a booked test or repairs.

How thin can brake pads get before they fail an MOT?

Brake pads fail the MOT below 1.5mm. Worn or pitted brake discs and thin brake pads are among the most common advisories, so check them before your test.

The Most Common MOT Failures (and How to Avoid Them)

What fails most

Lights and electrics fail more MOTs than anything else, with 9.9% of tests failing on them. Suspension (7.9%), brakes (5.9%) and tyres (5.5%) follow. Many of these fails are bulbs, wipers and tyres you can check yourself before you buy.

Walk round the car with a helper. Check every bulb, including indicators, brake lights and the number plate light, then test the wipers and washer jets. Look closely at the tyres. The legal minimum is 1.6mm of tread across the central three-quarters, so use a tread depth gauge rather than guessing.

Brakes and suspension need a closer look. The most common advisories are tyres worn close to the legal limit, brake discs worn or pitted, tyres cracking or perishing, and brake pads wearing thin. Brake pads fail below 1.5mm, so get them measured if you're unsure. Repeat advisories on the MOT history show what has been left unfixed, so check it before you agree a price.

Checks you can do before the test

Lights and electrics fail more MOTs than anything else. They account for 9.9% of tests, followed by suspension, brakes and tyres. The good news is that many of these fails are bulbs, wipers and tyres you can check yourself before you pay a penny.

Walk round with the seller and check: - Every light works: headlights, indicators and brake lights. - The washer squirts and the wipers clear the glass cleanly. Top up the fluid if needed. - Each tyre has at least 1.6mm of tread across the central three-quarters. Use a tread gauge. - No warning light stays on once the engine is running.

Brake pads fail below 1.5mm, so ask when the brakes and tyres were last looked at. Check the plate fits the car's age too: a private plate can make a car look older, never newer. The newest is the 76 plate, from 1 September 2026. If anything doesn't add up, check the MOT history free at GetFreeCarCheck before you go further.

Which cars fail most

Older cars fail more. The average car fails 28.4% of first MOT tests, and the older the car, the more worn parts it has to show. Lights and electrics lead at 9.9% of tests, then suspension at 7.9%, brakes at 5.9% and tyres at 5.5%.

Many of these fails are easy to spot before you buy. Check the bulbs, wipers and tyres yourself. Tyres need at least 1.6mm of tread across the central three-quarters, and brake pads fail below 1.5mm. Cracked or perishing tyres and worn brake discs are common advisories, so ask the seller about them.

Our reliability index shows how models and years compare, so you can see which cars tend to need more repairs before you view one. Then check the MOT history of the car you're considering, looking for any drop in mileage between tests.

The most common MOT failures