In the UK, the minimum legal tyre tread depth is 1.6mm across the central three-quarters of the tyre. Driving with worn tyres can result in a £2,500 fine and 3 penalty points — per tyre. More importantly, worn tyres dramatically increase stopping distances in wet conditions.
The 20p Coin Test
Insert a 20p coin into the main tread grooves of your tyre. If you can see the outer band of the coin, your tread is below 3mm and you should consider replacing the tyre soon. If the band is hidden, your tread is above 3mm and legally acceptable.
Where to Check
Check tread depth in at least 3 places around the circumference of each tyre, and across the full width of the tread. Uneven wear can indicate alignment problems, incorrect tyre pressure, or suspension issues.
Reading Tyre Wear Indicators
All modern tyres have built-in tread wear indicators — small raised rubber bars moulded into the base of the tread grooves. When the tyre surface is level with these bars, the tyre is at the legal minimum and must be replaced.
When to Replace Earlier
Most tyre safety experts recommend replacing tyres at 3mm, not the legal minimum of 1.6mm. Research shows that stopping distances in wet conditions increase significantly once tread falls below 3mm. A tyre at 1.6mm can take up to 44% longer to stop in the wet compared to a tyre at 3mm.
