Working out whether a tyre is legal takes only a couple of minutes. There are six things to check, and a tyre that fails any one of them is illegal and should be dealt with before driving further.
The six checks
1. Tread depth. The tread must be at least 1.6mm across the central three-quarters of the tyre, all the way around. If any part of that band is below the limit at any point, the whole tyre is illegal. The full tread-depth rule covers exactly how it is measured.
2. Damage. Look for cuts, lumps, bulges, cracks or exposed cord. Any of these makes a tyre illegal and unsafe regardless of how much tread remains, because the structure itself is compromised.
3. Size and rating. The tyre must be a suitable size for the vehicle and meet its required load index and speed rating. A tyre that is the wrong size, or rated below what the car needs, is not legal.
4. Mixing. Tyres of different construction, radial and cross-ply, must not share an axle, and tyres on the same axle should match. This rarely applies to modern cars but remains the law.
5. Fitment. A directional or asymmetric tyre fitted the wrong way round is incorrectly fitted and will fail an MOT, as well as performing poorly.
6. The TPMS light. On cars first used from 2012, a tyre pressure monitoring warning light that stays on signals a fault, which is a major MOT failure and a sign a tyre may be losing pressure.
What about age?
Tyre age is not in itself illegal for cars and vans, so it is not on the checklist as a legal test. It is still worth noting: rubber ages even unused, replacement by around ten years is widely advised, and there is a legal age limit for the front axles of larger vehicles such as HGVs and buses.
If a tyre fails any check
A tyre that fails any of the six is illegal, and the consequences are not trivial: a fine and penalty points for every illegal tyre, an MOT failure, and a possible invalidated insurance claim after an accident. The sensible response is simple, stop using the tyre and have it replaced before driving on, with a fresh, legal set ordered online from the likes of Tyres.co.uk.
From the workshop: most people only think about tread, but damage and the TPMS light catch out just as many. If a tyre fails any one of the six, it does not matter how good it looks otherwise; it needs sorting before the car goes back on the road.
Sources and accuracy. Each checklist item reflects UK law and MOT requirements at the time of writing, which can change. Anything safety-critical should be confirmed against current official DVSA and GOV.UK guidance. If anything here looks wrong, get in touch and we will check it and put it right.
Common questions
How do I know if my tyre is illegal?+
Check six things: tread depth below 1.6mm, visible damage or exposed cord, the wrong size or rating for the vehicle, mixed constructions on an axle, a directional or asymmetric tyre fitted the wrong way, and a tyre pressure warning light on cars from 2012.
Is a tyre illegal if only one part is worn?+
Yes. If any part of the central three-quarters of the tread is below 1.6mm at any point around the tyre, the whole tyre is illegal, even if the rest still has good tread.
Is a damaged tyre illegal even with good tread?+
It can be. Cuts, bulges, lumps or exposed cord make a tyre illegal and dangerous regardless of tread depth, because the structure is compromised. Such a tyre should be replaced, not driven on.
What should I do if a tyre is illegal?+
Stop using it and have it replaced before driving further. An illegal tyre risks a fine and points per tyre, an MOT failure, and an invalidated insurance claim after an accident, so it is not worth the risk.