The Legal Minimum Tread Depth in the UK
In the UK, the legal minimum tyre tread depth is 1.6mm across the central three-quarters of the tread, around the full circumference. Driving with tyres below this limit carries a fine of up to £2,500 and three penalty points per tyre — plus the serious safety risks of reduced grip in wet conditions. Most safety experts recommend replacing tyres before they reach 3mm depth, where wet-weather performance degrades significantly.
You can check your tread depth using a 20p coin. Insert it into the main tread groove — if you can see the outer band of the coin (about 2mm), your tyres are approaching or below the legal limit and should be replaced immediately.
Visual Warning Signs to Watch For
Beyond tread depth, watch for these warning signs: bulges or bubbles in the sidewall (these indicate structural failure and the tyre should not be driven on); cracks in the sidewall (caused by age and UV exposure); uneven tread wear (scalloping, centre wear, or edge wear indicating alignment, pressure, or suspension issues); and visible tyre cords or steel belt showing through the rubber.
Most passenger tyres also have tread wear indicators — small raised bars in the bottom of the main tread grooves. When the tyre surface is flush with these bars, you're at 1.6mm and the tyre is legally at its minimum. Replacement is overdue at this point.
Age-Related Tyre Replacement
Even tyres with adequate tread depth should be replaced if they are more than 5–6 years old. Rubber degrades with age regardless of use, losing elasticity and grip. Check the DOT code on the sidewall — the last four digits indicate the week and year of manufacture (e.g., 2823 = 28th week of 2023). Call Slick Mobile Tyres for an assessment and mobile tyre replacement if your tyres are showing any of these signs.
- Legal minimum: 1.6mm tread depth
- Safety recommendation: replace at 3mm
- Check with the 20p test
- Replace tyres over 6 years old regardless of tread