The 1.6mm Rule
In the UK, the legal minimum tread depth is 1.6mm, measured across the central three-quarters of the tyre's width, and around the entire circumference — not just at one point.
That last part catches a lot of drivers out. A tyre can look fine at a glance and still be illegal if there's a worn patch somewhere else around the tyre, particularly on the inner or outer edge from alignment issues.
The 20p Test
The easiest way to get a rough check at home is the 20p test. Insert a 20p coin into the tread groove — if the outer rim of the coin is covered by tread, you're likely above the legal limit. If you can see the full rim, it's time to get the tyre checked properly.
This test is a good early warning system, but it's not precise. For an accurate reading, a tread depth gauge (or a quick check from a tyre fitter) is far more reliable, especially if you're close to the limit.
Need this sorted rather than just explained? Not sure where your tyres stand? We can check tread depth on the spot and give you an honest answer — no obligation to buy anything.
Call 07348 464775 or 0117 452 1024 — we come to you, 24 hours a day.
What Happens If You Don't Comply
Driving on tyres below the legal limit isn't just risky — it's a specific offence. Each illegal tyre can carry a fine of up to £2,500 and 3 penalty points, meaning a car with all four tyres below 1.6mm could theoretically rack up 12 points in one stop.
Beyond the legal side, worn tread genuinely affects how your car handles, especially braking distance in the wet. Tread channels water away from the contact patch — the shallower the tread, the less grip you have when it matters most.
When to Actually Replace
Most tyre professionals recommend replacing before you hit the legal minimum, not right at it — somewhere around 2-3mm is a sensible point to start budgeting for new tyres, particularly heading into autumn or winter when wet-weather performance matters most.
← Back to all articles