Tyres are among the most scrutinised parts of an MOT, and one of the most common reasons cars fail. The tester works through several specific checks, and the result is graded rather than a simple pass or fail.
What the tester checks
The MOT inspection covers a tyre's safety on several fronts:
- Tread depth: measured against the 1.6mm legal minimum across the central three-quarters and around the tyre
- Condition: cuts, lumps, bulges, cracks, and any exposed cord or ply
- Size and type: that the tyre is a suitable size and rating for the vehicle, and that constructions are not mixed across an axle
- Fitment: that the tyre is correctly seated and not fouling the vehicle, and that directional or asymmetric tyres are fitted the right way
- Valve: its condition and security
- TPMS: the tyre pressure monitoring system, on cars first used from 2012
A tyre that is visibly and severely under-inflated can also be failed, as low pressure affects how the car handles.
The TPMS check
Since the MOT was updated, the tyre pressure monitoring system is part of the test for cars first used from 1 January 2012. If the system is faulty or not working, most obviously shown by the horseshoe-shaped warning light staying on, the car fails as a major defect. A TPMS light is therefore not something to ignore in the run-up to a test.
How tyre defects are graded
MOT results use defect categories, and where a tyre falls decides the outcome:
| Category | Result | Example |
|---|---|---|
| Dangerous | Fail | Exposed cord or ply, a serious cut or bulge |
| Major | Fail | Tread below 1.6mm, wrong size, TPMS not working |
| Minor | Pass, noted | A small fault not yet affecting safety |
| Advisory | Pass, noted | Tread getting low, e.g. nearing the limit |
A Dangerous or Major defect is a fail. A tyre just above the limit, say at 1.7mm, will often pass with an Advisory that flags it is likely to fail next time, a useful prompt to get it replaced sooner, before the next test, a fresh set is quick to order online from Tyres.co.uk.
What is not checked
The spare wheel is not part of the MOT, so it is not inspected. That is no reason to neglect it: a spare must itself be legal and in good condition if it is ever pressed into use, so it is worth a separate check, especially before a long trip.
From the workshop: most tyre fails we see were avoidable with a five-minute look the week before. Tread, a glance for damage, and making sure no warning lights are on covers the bulk of it, and it is far cheaper than a retest and a last-minute tyre.
Sources and accuracy. The MOT checks, the TPMS rule and the defect categories described here reflect the MOT testing requirements at the time of writing, which can change. Anything safety-critical should be confirmed against the current official DVSA guidance. If anything here looks wrong, get in touch and we will check it and put it right.
Common questions
What do they check on tyres in an MOT?+
The tester checks tread depth against the 1.6mm limit, the tyre's condition for cuts, bulges and exposed cord, that the size and type are correct and matched across each axle, the valve, and on cars from 2012, the tyre pressure monitoring system.
Is TPMS part of the MOT?+
Yes, for cars first used from 1 January 2012. If the tyre pressure monitoring system is faulty or not working, usually shown by a warning light, the car fails the MOT as a major defect.
What are the MOT defect categories for tyres?+
Dangerous, Major, Minor and Advisory. Dangerous and Major defects are a fail. A tyre below 1.6mm or of the wrong size is a major fail, while exposed cord or serious damage is dangerous.
Is the spare tyre checked in the MOT?+
No. The spare wheel is not part of the MOT test, so it is not inspected. It is still worth checking separately, since a spare must be legal and serviceable if it is ever fitted to the car.