11/10/2026
A simple 20p coin could help motorists spot a potentially costly problem in seconds.
It can stop people from driving on tyres that are close to (or already below) the legal limit which can lead to expensive repair bills or potentially fines if stopped by the police.
As roads get wetter and temperatures drop from October onwards, worn tyres are more likely to struggle with surface water.
That can increase the risk of aquaplaning on faster roads and in standing water, so checking tread depth becomes even more important in persistent rain.
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 a car with bald tyres can risk a fine of £2,500 and three penalty points - and that’s per tyre, too. If all four tyres are worn below the legal limit, you could potentially be summoned to court, lose your licence and face a £10,000 fine."
What is the minimum tyre tread depth?
The legal minimum depends on the vehicle, but the tread must meet the standard across a continuous band around the full circumference of the tyre. For cars, caravans and vans, tyres must be “at least 1.6 mm” — although many safety bodies recommend replacing tyres earlier, with 3mm often cited as a safer point to act.
That’s because performance can drop off quickly once tread gets low, particularly in wet conditions. The RAC said: "Tests by UK technical organisation MIRA found that, once tyres are below 3mm, stopping distances increase dramatically.
"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."
Can I test my tyre tread myself?
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 if you want a quick check, many motorists use a 20p coin as a guide. The idea is straightforward: 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."
✍Andrew Nuttall
