Key takeaways
- The most common tyre MOT failures are tread below the 1.6mm legal minimum and visible damage such as cuts, lumps and bulges.
- The tester also checks tyre size and type, security on the wheel, exposed cord or ply, and the valve condition.
- On cars first used from 1 January 2012, a tyre pressure monitoring (TPMS) warning is an MOT failure.
- Most tyre MOT failures are easy to spot with a quick check beforehand, so they are largely avoidable.
Tyres are one of the most common reasons cars fail their MOT, and almost every tyre failure is avoidable with a five-minute check beforehand. The MOT inspects each tyre against the DVSA MOT testing manual, covering tread, damage, size, security and the pressure warning light. Here are the faults that catch people out and how to spot them first.
What tyre checks are in the MOT?
During the MOT, the tester examines each tyre for tread depth, condition, correct size and type, secure fitment and exposed cord, and checks the valve and the tyre pressure monitoring system where fitted. The standards come from the DVSA MOT testing manual. If any tyre falls short on these points, the car fails. Most of them you can check yourself in minutes.
Tread below 1.6mm
Worn tread is the tyre fault that catches most drivers out. The legal minimum tread depth is 1.6mm across the central three-quarters of the tread and around the whole circumference. If any part of that central band drops below 1.6mm, anywhere on the tyre, it fails the MOT and is illegal to drive on.
You can check quickly with the 20p test: if the outer band of a 20p coin is hidden when pushed into the main grooves, you are likely above the limit. Our guide to checking tread depth walks through it, and the legal tread depth rules explain the law.
Cuts, lumps, bulges and damage
The tester fails any tyre with a cut deep enough to reach the cords, or a lump or bulge that shows the structure has been damaged. A sidewall bulge usually means internal damage from hitting a kerb or pothole and the tyre must be replaced, it cannot be repaired. These are easy to miss because they often sit on the inner sidewall.
- Bulges or blisters in the sidewall, internal damage, replace immediately.
- Deep cuts or tears over a set length that expose the plies.
- Lumps caused by impact damage.
Run your hand around both sidewalls, including the inner face, to find damage you cannot see from outside. Our guide to sidewall damage explains why these cannot be repaired.
Wrong size, type or exposed cord
A tyre fails if it is the wrong size or type for the vehicle, if the two tyres on an axle are different sizes or different structures, or if the ply or cord is exposed anywhere. Mismatched tyres across an axle and incorrect speed or load ratings are common surprises after someone has had a single tyre replaced cheaply elsewhere.
| Failure item | What the tester looks for |
|---|---|
| Tread depth | Below 1.6mm in the central three-quarters |
| Damage | Cuts to the cords, lumps, bulges |
| Exposed cord/ply | Visible cords or ply anywhere |
| Size and type | Wrong size, mismatched across an axle |
| Security and valve | Loose tyre, badly seated, damaged valve |
| TPMS (2012+) | Warning light on or system not working |
The TPMS warning light
On cars first used on or after 1 January 2012, a faulty tyre pressure monitoring system is an MOT failure. If the TPMS warning light stays on, the car fails. The light can come on from a genuine low tyre, a failed sensor or a flat sensor battery, so do not just ignore it before your test.
Check your pressures first, as a simple top-up often clears it. If the light stays on with correct pressures, a sensor may need replacing, see our guide to the TPMS warning light and our TPMS replacement service.
Other tyre points to check before the test
Beyond the headline items, a few less obvious points catch drivers out. They involve the valve, how the tyre sits on the rim and any old repairs, so they are easy to overlook. The tester only inspects the tyres on the road wheels, not the spare, but a quick look at each of these closes the gaps before test day.
- Damaged or perished valve: a valve so badly damaged or misaligned that it could let the tyre deflate suddenly is a failure, and a cracked stem also causes slow pressure loss.
- Tyre not seated or fouling: a tyre sitting badly on the rim, or one rubbing on the bodywork or suspension, is a failure.
- Old repairs: the tester judges the tyre's condition rather than its paperwork, but a plug in the shoulder or sidewall is a warning sign in itself, because a proper BS AU 159 repair only ever sits in the central tread area.
If a previous puncture repair worries you, our guide to whether a punctured tyre can be repaired explains the rules a safe, legal repair must meet.
Avoiding a tyre MOT failure
Almost every tyre MOT failure is preventable with a quick pre-test check: tread with a 20p coin, a look around all four sidewalls for damage, correct pressures and no warning lights. If you find a problem, Fast Tyre can fix it before test day. Our mobile tyre fitting service comes to your home or work across London and the surrounding counties, usually within 30 to 60 minutes, so you can pass first time.
Frequently asked questions
Tyres wear gradually, so many drivers do not notice tread dropping below 1.6mm or damage on the inner sidewall until the test flags it. Because the checks are visual and easy to overlook, tyres consistently rank among the top MOT failure items, even though they are simple to check beforehand.
Yes, on cars first used on or after 1 January 2012. If the tyre pressure monitoring warning light stays on, the car fails the MOT. Check your pressures first, as topping up often clears it. If the light persists, a sensor may have failed and need replacing before the test.
No. A lump or bulge in the sidewall shows internal structural damage and is an automatic MOT failure. The tyre cannot be repaired and must be replaced. Bulges often appear after hitting a kerb or pothole, so check both sidewalls, including the inner face, before your test.
At least 1.6mm across the central three-quarters of the tread and all the way round the tyre. Anything below that on any part of the central band fails. Many drivers replace at around 3mm for safety, as wet grip drops off sharply below that, well before the legal limit.
Not of a different size or structure. Two tyres on one axle that differ in size, or mix constructions such as radial and cross-ply, are an MOT failure and can affect braking and handling. Different brands are not a failure in themselves, but matching the pair is still the better choice. Keep each axle matched, and check the size and rating if you have had a single tyre replaced.
Do a five-minute check before the test: use a 20p coin to check tread is above 1.6mm, feel around all four sidewalls for cuts and bulges, set the correct pressures, and make sure no warning lights stay on. Fix any issue beforehand and you should pass first time.