A simple 20p coin check can help motorists spot potentially costly tyre problems in seconds, potentially avoiding fines of up to £10,000. As roads get wetter and temperatures drop from October onwards, worn tyres are more likely to struggle with surface water, increasing the risk of aquaplaning on faster roads and in standing water.
Why tyre tread matters in winter
The RAC advises drivers to keep a close eye on tyre condition, warning that tyres are “the only contact point between your vehicle and the road.” Because tread gradually wears down, a quick at-home check every couple of weeks – and before longer trips – can help catch issues early, without needing specialist tools.
The RAC said: “The tyres are the only contact point between your vehicle and the road. If your tyres are past their best, then the safety of your vehicle will be compromised.”
Driving with bald tyres can risk a fine of £2,500 and three penalty points – and that’s per tyre. If all four tyres are worn below the legal limit, drivers could potentially be summoned to court, lose their licence and face a £10,000 fine.
Minimum tread depth and the 20p test
The legal minimum tread depth depends on the vehicle, but for cars, caravans and vans, tyres must be “at least 1.6 mm” across a continuous band around the full circumference of the tyre. Many safety bodies recommend replacing tyres earlier, with 3mm often cited as a safer point to act.
Tests by UK technical organisation MIRA found that, once tyres are below 3mm, stopping distances increase dramatically. The RAC said: “The difference in wet braking distance between a tyre worn to 3mm and one worn to 1.6mm can be as much as 44%. Worn tyres are particularly dangerous in the wet because a tyre’s tread helps disperse water away from the contact patch between tyre and road. If there’s less tread depth, less water can be shifted, increasing the risk of aquaplaning and losing grip.”
Drivers don’t have to rely on a garage to keep tabs on tyre wear. A tread depth gauge can be picked up cheaply (often for under £10) and gives a more precise reading. But for a quick check, many motorists use a 20p coin as a guide: place the coin into the main tread grooves. If the outer rim is still visible, the tyre may be approaching unsafe levels and should be properly inspected.
The RAC said: “The 20p test is a simple, quick and easy way of checking the tyre tread of your car's wheels. Just take a 20p coin and insert it into the tread grooves on the tyre. If you can't see the outer band on the coin, your tyres are above the legal limit. However, if you can see the band and that section of the coin is still visible, your tyres could be unsafe and require professional inspection by a mechanic.”
