What the UK Tyre Tread Limit Actually Means (and How to Check Yours)

• The legal minimum tread depth for cars in the UK is 1.6mm across the central three quarters of the tyre and around its whole circumference, and a tyre below it risks a £2,500 ($3,375) fine and 3 penalty points.
• Slot a 20p coin into the main grooves in at least three places on each tyre: if the coin’s outer band is hidden, the tread is above the legal limit.
• Safety bodies say to replace tyres at 3mm rather than wait for 1.6mm, as wet stopping distances lengthen sharply once tread drops below that.

What the UK Tyre Tread Limit Actually Means (and How to Check Yours)

The legal minimum tread depth for cars, light vans and light trailers in the UK is 1.6mm. GOV.UK says the tread must reach that depth across the central three quarters of the breadth of the tyre and around its entire circumference, and the MOT inspection manual applies the same test to the primary grooves. You can check it in under a minute with a 20p coin: push it into the main grooves, and if the outer band on the coin is hidden by the tread, the tyre is above the legal limit. If the band is visible, the tyre is at or below it and needs a professional check.

That is the law. It is not the same as a safe tyre, and the gap between the two is where most of the real-world risk sits. The sections below cover how to run the coin test properly, what the penalties are, what the evidence says about stopping distances, and what replacing a tyre costs.

How the 20p Test Works and Where to Put the Coin

TyreSafe, the UK tyre safety charity, recommends the 20p test as the easiest way to confirm a tyre is above the legal minimum. The rim on a 20p coin is sized to match a 1.6mm depth, so the test needs no gauge and no tools.

Use the coin in the main tread grooves, which are the deepest and most continuous ones, rather than in the small cuts in the tread blocks. Push it in upright so the edge of the coin sits in the groove, then look at the outer band of the coin. If the band is hidden, the tread is deeper than 1.6mm at that spot. If you can see the band, it is not.

Test each tyre in at least three places: across the width of the tread and at different points around the circumference. Tyres rarely wear evenly. Misaligned wheels, under-inflation and worn suspension parts can all leave one edge or one section of the tread far lower than the rest, so a single good reading proves little. Tyre safety guidance suggests repeating the check roughly every two weeks and before any long trip, and the front tyres on a front-wheel-drive car are worth extra attention, as they usually wear fastest.

The law covers the central three quarters of the tread, so the outer quarter can legally be smooth. A tyre that has gone bald on its inner edge can still look fine from the driver’s side, so crouch down and check the inside shoulder of each front tyre and the outside.

What the Law Says and What It Costs You

Driving with a tyre below 1.6mm can bring a fine of up to £2,500 ($3,375) and 3 penalty points for each illegal tyre. Four illegal tyres could mean a maximum £10,000 ($13,500) fine and 12 penalty points, which is enough to put a licence at risk of a ban. Those are the maximums set out in UK guidance, and what a court actually imposes depends on the case, but the exposure is large compared with the cost of a tyre.

The tread limit also decides your MOT. The DVSA inspection manual for cars requires the primary grooves of the tread pattern to be at least 1.6mm deep within the central three quarters of the tread, and a tyre that falls short is a test failure. Checking your tyres with a coin a week or two before the MOT gives you time to shop around rather than accept the first quote from the test centre.

Tread depth is one check in a set. The same GOV.UK vehicle safety guidance covers tyre pressure, cuts, bulges and damage, and a tyre with a cut or bulge in the sidewall can be unsafe at any tread depth. If you see one, have it looked at before you drive any further.

Why Safety Experts Say Replace at 3mm, Not 1.6mm

Both TyreSafe and Continental recommend replacing tyres at 3mm. The argument is about wet roads. Tread is what clears water from under the tyre, and the less tread there is, the more likely a wedge of water builds up ahead of it and the tyre loses contact with the road.

Continental’s published summary of an AutoBild test in 2019 gives the clearest numbers. A VW Golf was fitted with 225/45 R17 tyres at different tread depths and braked on a very wet surface with ABS. From 80 km/h (50 mph), the Continental tyre stopped the car in 25.8 metres (85 feet) when new, 31.0 metres (102 feet) with 3mm of tread and 36.2 metres (119 feet) at the legal minimum of 1.6mm. From 120 km/h (75 mph), the stops were 59.1 metres (194 feet) new, 124 metres (407 feet) at 3mm and 154.9 metres (508 feet) at 1.6mm. Continental says the car on 1.6mm tyres would still be travelling at 106 km/h (66 mph) at the point where the new-tyre car had stopped.

TyreSafe points to separate MIRA testing in which cars on 1.6mm tread took up to 44 percent longer to stop in the wet than cars on 3mm. The charity says the gap can reach 10 to 12 metres in some conditions.

This is a contested area. Michelin has publicly rejected calls to raise the legal minimum to 3mm, saying there is no link between tread depths at 1.6mm and increasing accident rates, and arguing that changing tyres at 3mm is unnecessary and costly. The two positions are compatible for the driver: the law allows 1.6mm, but every test above shows wet grip falling away well before you reach it. If you do a lot of motorway miles or drive through winter, changing early is the lower-risk choice.

What New Tyres Cost and How to Plan the Spend

UK price guides for 2026 put budget tyres at about £45 to £70 ($61 to $95) each, mid-range tyres at £75 to £120 ($101 to $162), and premium tyres from £220 ($297) upwards, rising past £1,200 ($1,620) for some large or performance sizes. Fitting, balancing and disposal can add £25 to £45 ($34 to $61) per tyre where the retailer does not include it in the headline price. Most drivers pay £80 to £150 ($108 to $203) per mid-range tyre once fitting is included.

A worn set is a bill of several hundred pounds, which is why drivers tend to leave it late. Use the coin test as a planning tool, not just a pass or fail. When the coin shows the tread is getting low, you have time to compare online prices, book a fitting slot and avoid paying for an emergency replacement after a failed MOT or a puncture.

The rules for your next check come down to four numbers: 1.6mm is the floor the law sets, the 20p coin tells you whether you are above it, 3mm is where the safety bodies say to start shopping, and the fine for getting it wrong is up to £2,500 ($3,375) and 3 points per tyre. A coin and two minutes beside the car are all it takes.

Sources

• GOV.UK, Check your vehicle is safe to drive
• GOV.UK, MOT inspection manual: cars and passenger vehicles, axles, wheels, tyres and suspension
• TyreSafe, How to check tyre tread depth with a 20p coin
• TyreSafe, The complete guide to tyre tread depth
• Continental, Aquaplaning: minimum legal tread depth can prove fatal
• Automotive World, Michelin: changing tyres at 3mm unnecessary, costly and harmful to the environment
• Bumper, Tyre replacement cost guide 2026