Tyre Tread Depth Law UK: The Legal Minimum and How to Check It

The UK tyre tread depth law sets a legal minimum of 1.6mm for cars, measured across the central three-quarters of the tyre and around its entire circumference. Drop below that on any tyre and you are breaking the law: the penalty is a fine of up to 2,500 pounds and 3 penalty points per illegal tyre. The quickest way to check is the 20p test – slot a 20p coin into the tread grooves, and if you can see the coin’s outer band, your tread may be too low.

That is the short version, and if you have just bought your first car it is the bit to memorise. But there is a lot packed into those two sentences, and getting it wrong is expensive in more ways than one. Below I will walk you through exactly what the 1.6mm rule covers, why “per tyre” matters so much for a new driver, how the MOT test looks at your tyres, and the two ways to check your own tread on the driveway in under a minute. This is the stuff nobody teaches you in a driving lesson, yet it is your legal responsibility the moment the car is yours.

What is the legal tyre tread depth in the UK?

The legal minimum tread depth for cars, light vans and light trailers in the UK is 1.6mm. That figure is set out in the Highway Code (Annex 6), which 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.”

Two details in that sentence do the heavy lifting, and they are the parts people miss:

• Central three-quarters of the breadth. Picture the tyre split into four strips across its width. Only the middle two-and-a-half strips – the central three-quarters – legally have to hold that 1.6mm. The outer edges can be more worn without failing the legal limit, though heavy edge wear is a warning sign in its own right.
• The entire circumference. It is not enough for one patch to pass. The tread has to be at least 1.6mm the whole way round the tyre. A bald strip on one section fails the whole tyre, so it pays to roll the car forward and check in a few places.

Different vehicles have a different figure. Motorcycles, large vehicles and passenger-carrying vehicles have a lower minimum of 1mm across three-quarters of the breadth (again from Highway Code Annex 6). For the car most new drivers will be in, though, 1.6mm is the number that matters.

What is the penalty for illegal tyres?

Driving with a tyre below the legal limit can cost you up to 2,500 pounds and 3 penalty points – and that is for each illegal tyre, not per car. It is the “per tyre” wording that turns a small oversight into a serious problem, so it is worth spelling out.

How many illegal tyres	Maximum fine	Penalty points
1 tyre	up to 2,500 pounds	3 points
2 tyres	up to 5,000 pounds	6 points
3 tyres	up to 7,500 pounds	9 points
4 tyres	up to 10,000 pounds	12 points

Those fines are the maximums a court can impose rather than an on-the-spot ticket, but the penalty points are the part that should stop a new driver cold. Tyres tend to wear at a similar rate, so if one is over the limit the others often are too. Four worn tyres could mean 12 points from a single check.

That matters enormously in your first two years on a full licence. Under the Road Traffic (New Drivers) Act 1995, if you build up 6 or more penalty points within two years of passing your test, the DVLA revokes your licence and you go back to provisional – re-sitting both the theory and the practical test to get it back. For any other driver, reaching 12 points triggers a “totting-up” ban. Either way, letting your tyres go bald is one of the easiest ways to lose a licence you have only just earned. If you want the confidence to spot problems like this before they bite, that awareness is exactly the kind of thing a structured course builds in – it is part of why a proper Provisional refresher course covers vehicle checks alongside the driving.

How do I check my tyre tread with the 20p test?

The 20p test is the simplest DIY check, and you do not need any tools. Take a 20p coin and push it into one of the main grooves of the tyre. Look at the outer rim of the coin. If the raised outer band is hidden by the tread, you have more than the legal minimum. If you can see that band, your tread is getting close to or below 1.6mm and the tyre should be checked professionally.

The reason it works: the outer band on a 20p sits roughly 1.6mm to 2mm in from the edge of the coin, so it acts as a rough go/no-go gauge for the legal limit. It is not a precise measurement, but it is a brilliant early warning.

Here is how to do it properly:

1. Park on level ground and make sure the handbrake is on.
2. Pick the deepest-looking main groove (the big grooves that run around the tyre, not the fine sipes).
3. Insert the 20p so the edge of the coin points down into the groove.
4. Check whether the outer band is visible. Hidden means you are fine; visible means get it checked.
5. Repeat at the inner, middle and outer part of the tread, and at three or four points around the tyre. Roll the car forward half a turn to reach the bit that was on the ground.
6. Do all four tyres. Do not forget to include the spare if your car carries one, because a bald space-saver is no use the day you need to change a tyre at the roadside.

For an exact reading, a tyre tread depth gauge (a cheap analogue or digital tool from any motor factor) measures the groove in millimetres. Many tyres also have moulded tread wear indicators – small raised bars set into the base of the grooves at 1.6mm. When the surrounding tread wears down level with those bars, the tyre has reached the legal limit and needs replacing.

What tread depth do tyres need to pass an MOT?

Your tyres must have at least 1.6mm of tread to pass the MOT, using the same central-three-quarters-and-full-circumference standard as the road law. The DVSA MOT inspection manual states the tread “must be at least 1.6mm deep within the central three-quarters of the breadth of tread and around the entire outer circumference of the tyre.”

Here is the part worth knowing: a tyre worn below that limit is recorded as a Dangerous defect on the MOT. That is the most serious category the tester can give. A car with a dangerous defect fails the MOT, and you should not drive it away until the fault is fixed. Testers also check tyres for cuts, bulges, lumps, exposed cords and the correct size and type, and a warning light for tyre pressure monitoring can be flagged too.

If you are budgeting for running your first car, the MOT and a set of tyres are two costs to plan for. New tyres typically start from a bald tread of 7mm to 9mm, so a set replaced together should last a good while – but they are consumable, and they will come round again. It is one of the ongoing costs that surprises people, alongside insurance, tax and fuel, and it is worth factoring in when you are working out what learning to drive and then running a car really costs. Our guide on what an intensive driving course costs breaks down the learning side; tyres, tax and insurance are the “after you pass” side.

Should I replace my tyres before they hit 1.6mm?

Yes. The 1.6mm figure is the legal floor, not a target to aim for, and most tyre and safety experts recommend changing tyres well before then. The widely advised replacement point is 3mm, and many will tell you to start planning at 2mm.

The reason is grip in the wet. Tests by MIRA (the Motor Industry Research Association) found that at 1.6mm of tread, wet braking distances were up to 44% longer than at 3mm. That is not a rounding error – it is potentially several car lengths further to stop in the rain, at exactly the moment you can least afford it. Tread exists to channel water out from under the tyre so the rubber can grip the road. As it wears down, less water clears, grip falls away, and the risk of aquaplaning on standing water climbs.

Worn tyres are one of the quiet reasons a car handles badly in bad weather, and it is why keeping an eye on tread is part of driving safely rather than just passing the MOT. If wet-weather and low-grip driving is something you want to feel more sure about after you pass, that is exactly what schemes like Pass Plus are designed to build – real practice in the conditions where tread depth matters most.

Where do tyres wear fastest, and what does uneven wear mean?

Tyres rarely wear evenly, and the pattern tells you something. If the tread is going down faster on the inner or outer edge while the middle looks fine, that often points to wheel alignment being out, or to worn suspension or steering components. If the centre wears faster than the edges, over-inflation can be the cause; if both edges wear faster than the centre, under-inflation is a common culprit.

The Highway Code (Annex 6) makes the pressure point directly: tyres “MUST be correctly inflated to the vehicle manufacturer’s specification for the load being carried,” and it warns that “excessive or uneven tyre wear may be caused by faults in the braking or suspension systems, or wheels which are out of alignment.” The takeaway for a new owner: correct tyre pressures (you will find the recommended figures in the driver’s door shut, the fuel-filler flap or the handbook) do not just help fuel economy, they make your tyres last longer and wear evenly. If you spot lopsided wear, get the alignment and suspension checked rather than just fitting a new tyre that will wear the same way.

Front or rear – which tyres wear first?

On most cars it is the front tyres that wear faster. The front tyres do the steering, take the braking load and, on a front-wheel-drive car (which is most small cars new drivers buy), put the engine’s power down as well. It is common to be replacing fronts while the rears still have plenty of tread.

That is normal, but check all four anyway – the legal limit and the MOT apply to every tyre on the car, spare included where fitted. Some drivers rotate tyres front to back to even out the wear; if you are unsure, a garage will advise. The one thing not to do is assume the backs are fine because the fronts look worst. Give each tyre the 20p test.

Getting comfortable with your first car

Passing your test is the milestone, but the weeks after are when the real learning starts – insurance, tax, fuel, and jobs like this that were never on the syllabus. None of it is complicated once someone shows you, and a five-second groove check every few weeks is one of the cheapest bits of safety going.

At GetMyPass, our intensive driving courses are built to get you test-ready fast, with an instructor who will happily talk you through the practical side of car ownership as well as the driving itself. If you are close to test standard and just need to sharpen up, take a look at how our courses work, or get started with a course when you are ready. And if it is nerves rather than skill holding you back, our guide on building driving confidence is a good place to start.