- The legal minimum for cars, light vans and light trailers is 1.6mm across the central three-quarters of the tread, around the whole circumference.
- Police can give a fine of up to £2,500 and 3 penalty points for each illegal tyre.
- Cuts, bulges, lumps and exposed cords also make a tyre illegal, whatever the tread depth.
- Grip in the wet falls as tread wears, so many drivers replace well before 1.6mm.
- Check pressures when the tyres are cold, against the figures for your car and its load.
What is the legal tread depth in the UK?
For cars, light vans up to 3,500kg and light trailers, the Highway Code says tyres must have a tread depth of at least 1.6mm across the central three-quarters of the breadth of the tread, and around the entire circumference. The outer edges are not part of the measurement, but the whole of the middle band must be legal, not just one spot.
Motorcycles, large vehicles and passenger vehicles with more than 8 passenger seats have a lower minimum of 1mm. These rules come from the Highway Code, which covers England, Scotland and Wales, and Northern Ireland uses the same 1.6mm minimum for cars.
What are the penalties for illegal tyres?
The penalty is applied per tyre. Government road safety guidance from THINK says you could get a fine of up to £2,500 and 3 penalty points for each illegal tyre. Four worn tyres could mean 12 points, which is enough to lose your licence.
Worn or damaged tyres also make a car unsafe, and a tyre defect found at the MOT is a fail. If you are in a crash on illegal tyres, it can cause problems with your insurer.
How to check your tread depth
You do not need special skills to check your tyres. Do it once a month and before long journeys, with the car parked on flat ground and the steering straight. Turn the wheel fully to one side to see the front tyres more easily.
- Tread wear indicators: small raised bars at the bottom of the main grooves, set at 1.6mm. If the tread is level with them, the tyre is at the limit
- Tread depth gauge: an inexpensive tool from any car shop that gives an exact reading in millimetres
- Check at least three places across the tyre and at several points round it
- Look for uneven wear, such as one edge worn more than the other
- Do not forget the spare if your car has one
Does the 20p test work?
The 20p test is a quick rough check, not a legal measurement. Put a 20p coin into the main grooves of the tread. If you can see the outer band of the coin, the tread may be close to or below the legal limit, and you should check properly with a gauge or have a fitter look.
If the band is hidden, the tyre is probably above the limit at that point. Try several places, because tyres rarely wear evenly. A gauge or the wear indicators give you a clearer answer.
Damage that makes a tyre illegal
Tread depth is only part of the law. Tyres must also be free from certain cuts and other defects. At the MOT, a cut deep enough to reach the ply or cords is a major fault, and a lump, bulge or tear caused by the structure failing is a dangerous fault.
- Bulges or lumps in the sidewall, often after hitting a kerb or pothole
- Cuts in the tread or sidewall, especially where cords show
- Exposed cords or wire
- Cracking in the rubber, a sign of age or long periods standing still
- Different tyre structures, such as radial and cross-ply, mixed on the same axle
How old is too old for a tyre?
There is no legal age limit for car tyres in the UK. Since February 2021, tyres aged 10 years or more have been banned on the front steered axles of lorries, buses and coaches, and on single wheels of minibuses. That rule does not cover private cars.
Rubber still hardens and cracks with age, even on a tyre with plenty of tread, such as a spare or one on a car that is rarely driven. You can find the age on the sidewall: a four-digit code where the first two digits are the week and the last two the year it was made. Ask a fitter to check older tyres.
Tyre pressures and why they matter
Under-inflated or over-inflated tyres affect braking distance, steering, fuel use and how fast the tyre wears. The Highway Code says tyres must be inflated to the manufacturer's specification for the load being carried. That figure is usually in the handbook, inside the driver's door frame or on the fuel filler flap.
Check pressures at least every couple of weeks and before a long trip, when the tyres are cold. A car loaded with passengers and luggage often needs a higher pressure. If one tyre keeps losing air, it may have a slow puncture.
How AYS can help
If your tyres are close to the limit or damaged, a mobile tyre fitter can come to your home or work. On AYS Concierge you enter your postcode and the job, and local fitters can send a free quote with no obligation. Give your tyre size from the sidewall so the quote matches the tyre you need.
Questions people also ask
Is 2mm of tread legal?
Yes, 2mm is above the 1.6mm legal minimum for cars, as long as that depth is across the central three-quarters of the tread and all the way round the tyre. Stopping distances in the wet grow as tread wears, so at 2mm it is worth planning a replacement soon, especially before winter or a long journey.
Will my car fail its MOT on tyres?
It will fail if any tyre has less than the legal tread depth, has a cut reaching the cords, has a bulge, lump or tear, or if tyres of different sizes or structures are fitted on the same axle. Checking the tread, sidewalls and pressures a few days before the MOT gives you time to sort any problems.
Do I need to replace tyres in pairs?
It is not a legal requirement, but tyres on the same axle should be the same size and structure, and similar tread depth helps the car handle evenly. If one tyre is worn and the other on that axle is also getting low, replacing both makes sense. A fitter can measure both and advise.
How often should I check my tyres?
Check tread depth and look over the sidewalls about once a month, and check pressures every couple of weeks and before any long journey, with the tyres cold. Also check after hitting a kerb or deep pothole, as a bulge can appear later. Regular checks catch slow punctures and uneven wear early, which often points to a tracking problem.
- GOV.UK: The Highway Code, Annex 6 vehicle maintenance
- THINK: Vehicle safety checks
- GOV.UK: MOT inspection manual, axles, wheels, tyres and suspension
- GOV.UK: Government bans old coach, bus and lorry tyres
Rules can change. Check the official pages above for the latest position.
