Motorists can avoid a £2,500 fine this October by using a simple 20p coin to check their tyre tread depth at home, according to a tyre expert. Vehicles on UK roads must have a minimum tyre tread depth of 1.6mm, and the coin test offers a quick way to judge whether tyres are above the legal limit.
The 20p coin test
James Harding, tyre expert at BlackCircles, said checking tread regularly is one of the simplest ways drivers can protect their safety. He explained that tread depth affects how well a tyre grips the road and how quickly a vehicle can stop, particularly in wet conditions. As tyres wear down, their ability to disperse water reduces, increasing braking distances and the risk of aquaplaning.
To perform the test, insert a 20p coin into the main tread grooves at several points around each tyre. If the outer band of the coin is hidden, the tread is above the legal minimum at that point. If the outer band is visible, the tyre may be at or below the legal limit and should be checked more accurately.
Fines for illegal tyres
Driving with a tyre below the legal 1.6mm limit can lead to a £2,500 fine for each individual tyre. This means four tyres under the limit could leave motorists facing a £10,000 penalty.
The Blackcircles 2026 Tyre Knowledge Report found that around three-quarters of road users described themselves as somewhat or very confident in their tyre knowledge. However, only 49% correctly identified 1.6mm as the legal minimum tread depth. Almost a third of drivers polled (32%) incorrectly thought the minimum was 2.5mm, while 19% said they did not know.
