Your tyres are the only part of your car that touches the road, so their condition affects grip, braking and safety more than almost anything else. Checking them takes less than a minute, and you only need a 20p coin.
The 20p test
Take a 20p coin and push it into the main tread grooves of the tyre. If the outer band of the coin is hidden by the tread, you have plenty left. If you can see the outer band, your tyre may be close to or below the legal limit and should be checked by a professional. Do this across the width of the tyre and at a few points around it, because tyres do not always wear evenly.
What the law says
In the UK the legal minimum tread depth is 1.6 mm across the central three quarters of the tyre and around its full circumference. Driving on tyres below this is illegal and dangerous, and you can be fined and given penalty points for each illegal tyre. Many experts suggest changing tyres at around 3 mm, well before the legal limit, because wet grip falls off sharply as tread wears down.
Other things to look for
- Uneven wear. More wear on one edge can point to wheel alignment or suspension issues.
- Bulges or lumps. These can appear after hitting a kerb or pothole and mean the tyre should be replaced.
- Cracks in the sidewall. A sign of age or damage that weakens the tyre.
- Objects in the tread. A nail or screw may be causing a slow puncture.
Do not forget pressures
Under inflated tyres wear faster, use more fuel and handle poorly. Check pressures when the tyres are cold and set them to the figures in your handbook or the sticker in the door shut. It is a two minute job that saves money and extends tyre life.
When to replace
If the 20p test is borderline, the tread is uneven, or you have spotted damage, get the tyres looked at. We can measure the tread accurately, advise honestly and fit new tyres if needed. There is more on our tyres and puncture repair page, including same day puncture repair for drivers around Guildford.
Book with your local Guildford garage
SMA Autos LTD is an independent garage in Normandy, Guildford, looking after drivers across Guildford, Worplesdon, Ash, Pirbright, Fairlands and the wider Surrey area. For honest advice and a clear price before any work starts, book online or call us on 07921 814250.