Tyres are the only thing connecting your car to the road, so tread depth is not something to take lightly. UK law sets a clear minimum, and falling below it can land you with a fine of up to £2,500 per tyre, three penalty points on your licence, and dramatically longer stopping distances when the road is wet. Here is everything you need to know about the rules, how to check your tread at home, and when to book a replacement.
What the Law Says About Minimum Tread Depth
For cars, light vans, and light trailers in the UK, the legal minimum tread depth is 1.6 mm across the central three-quarters of the tyre, all the way around. Brand-new tyres start with roughly 8 mm of tread, giving you about 6.4 mm of usable life before they need replacing.
The consequences of driving on illegal tyres are harsh: up to £2,500 and 3 penalty points per tyre. If all four tyres are below the limit, that is a potential £10,000 fine and 12 points, which is enough to lose your licence. On top of that, your insurance may refuse to pay out if you have an accident on tyres below the legal threshold.
Most tyre safety experts and manufacturers actually recommend fitting new tyres at 3 mm rather than waiting for the legal limit. At 1.6 mm, wet braking distances can be up to 44 percent longer than they are at 3 mm.
The 20p Coin Test: A Quick Home Check
The simplest way to see whether your tyres are getting close to the limit is the 20p coin test:
- Push a 20p coin into the main tread grooves of the tyre.
- If the outer band of the coin (which is 1.6 mm wide) disappears completely into the groove, your tread is above the legal minimum.
- If you can still see the outer band, your tread may be at or below 1.6 mm. Get the tyre inspected as soon as possible.
Test several spots around the tyre and across its width, because wear is not always even. You can also pick up a dedicated tread depth gauge from a motor factor for about £5, which gives you an exact reading in millimetres.
Get free quotes from qualified mechanics near you — no obligation, response within 48h.
Get my free quote →What Different Wear Patterns Tell You
The way your tyres wear can flag problems with the car itself:
- Even wear right across the tread: This is normal and means the tyre is wearing as it should.
- Both outer edges worn, centre fine: The tyre has been under-inflated. The soft sidewalls take too much of the load.
- Centre worn, edges fine: Over-inflation. Only the middle of the tyre has been making proper contact with the road.
- One edge worn more than the other: A wheel alignment or suspension problem. The wheel is sitting at the wrong angle.
- Patchy or scalloped wear: Often caused by worn shock absorbers, which let the wheel bounce on the road surface.
Uneven wear shortens tyre life and can be a sign of a bigger, more costly issue underneath. A garage can check your tyres and advise whether you need a wheel alignment or a suspension inspection.
When Is It Time to Replace Your Tyres?
Swap your tyres when the tread hits 3 mm (or straight away if it reaches 1.6 mm). You should also replace any tyre with bulges, cuts, or sidewall damage no matter how much tread is left, because these defects can lead to a blowout.
Age matters too. Most manufacturers suggest replacing tyres that are older than 5 to 6 years, even if the tread looks fine. Rubber degrades over time, especially on cars that sit in direct sunlight. You can find the manufacture date stamped on the tyre sidewall as a four-digit code (for example, 2319 means week 23 of 2019).
When fitting new tyres, always put two matching ones on the same axle. Having different tyre brands or types on the same axle can cause unpredictable handling, particularly on wet roads.