Motoring specialists are warning UK drivers that failing a simple 20p coin test could lead to fines of up to £10,000 and 12 penalty points on their licence. The test, promoted by National Highways, checks tyre tread depth, which is especially critical during hot weather when tyre blowout risks increase.
How the 20p Test Works
To perform the test, insert a 20p coin into the main grooves of the tyre. If the outer rim of the coin is hidden, the tread depth is legal (at least 1.6mm). If the rim is visible, the tyre may be below the legal limit and should be inspected or replaced. Drivers should check multiple points around each tyre, as wear is often uneven.
Legal Requirements and Penalties
UK law requires a minimum tread depth of 1.6mm across the central three-quarters of the tyre. Failing to meet this can result in a fine of up to £2,500 and three penalty points per tyre. As the RAC states: "Driving a car with bald tyres can risk a fine of £2,500 and three penalty points. That's per tyre, too." If all four tyres are illegal, drivers could face a court summons, loss of licence, and a £10,000 fine.
Hot Weather Risks
With UK temperatures forecast to reach 35°C, warm weather can overload cooling systems, accelerate battery fluid evaporation, and increase tyre blowout risks due to rapid air expansion. Tyres are the only contact point with the road, making proper tread essential for water drainage, traction, and safe stopping distances.
Consequences of Accidents on Illegal Tyres
The RAC warns that driving with illegal or bald tyres can invalidate insurance claims. "Any insurance claim as a result of an accident could be invalidated, so potentially your insurer won't pay out any money needed for repairs," it states. Additionally, drivers risk fines and penalty points as outlined above.
Additional Tyre Checks
Motorists should also inspect tyre walls for cracks, bulges, or defects. The AA notes that new tyres start with about 8mm of tread, and monthly checks are advised once tread wears to 4-5mm. Replacement is recommended at 3mm, with 1.6mm being the legal minimum. Tyre tread gauges or colour-coded tools can help assess depth at a glance.
