UK Tyre law

Whatever vehicle you're driving, the condition of your wheels is key to your safety.

It's the law to stick to a minimum tread depth and with good reason - your tyres are the only part of your vehicle in contact with the road.

What is the legal tyre tread depth?

The legal minimum tyre tread depth varies by each type of vehicle.

Testing your tread depth

Learn how to check the tread and pressure and then check out our general advice on maintaining tip top tyres.

Tread wear indicators

The easiest way to check your tyre tread is still legal is to look out for tread wear indicators. These are usually small bars, about 5mm wide, across the base of the tyre's main grooves.

If the tyre tread has become level with the top of the wear indicator, it means your tyres have reached the legal limit of 1.6mm. When they are worn to this level, they need to be replaced.

The 20p test

If your tyres don't have tread wear indicators, then you can test them with the 20p tyre test. To do this, all you have to do is place a 20p coin into your tyre’s tread grooves. The outer rim of a 20p coin is just under 3mm wide so if it's obscured then your tyre is comfortably above the legal minimum tread depth.

If you can see part of the rim of the coin then it's time to check your tyres more carefully using a proper tyre tread depth gauge.

Tyre gauges

The best method for testing your tyres is to use a calibrated tyre gauge. These come in many different forms – from digital gauges to laminated cards with coloured indicators.

To use, just place the gauge into the tyre’s groove and see how close you are to reaching the required minimum depth for your vehicle.

If you check the tread regularly and at different places across the tyre you'll be able too see how the tyres are wearing and pick up any early signs of uneven wear.

What causes tyre wear?

Tyres will start to wear out over time, but some factors can increase the wear. 

• Front tyres wear faster because of movement through steering and tyres on driven wheels will wear more quickly.
• High speed driving increases temperature and wear.
• Driving with an excess load. 
• Pressure – under inflation (through increased flexing and temperature) and over inflation (through reduced contact area) can both increase wear. 

Dangers of driving with a low tyre tread

Driving on tyres with tread below the legal limit or even worse, driving with bald tyres where the tread has worn away altogether can be incredibly dangerous, as well as illegal.

Hazards of driving with insufficient wear include:

• not being able to brake as quickly on wet roads
• a greater risk of aquaplaning
• not being able to gain traction on icy roads or snow
• being more vulnerable to punctures, which can lead to a sudden blowout.

What if I get into an accident with illegal or dangerous tyres?

If you’re involved in an accident and your tyres don’t meet the legal minimum standards, you risk any insurance claim you make being invalidated.

Not only that, driving with tyres considered dangerous because of insufficient tread also puts you at risk of a fine of up to £2,500 and 3 points on your licence.

And that’s just per tyre; if all 4 tyres are found to be dangerous, you could be looking at a £10,000 fine and 12 points.

Other legal tyre requirements

Because they play such a vital role, there are two specific requirements for legal tyres.

The first is that tyres must be fit for purpose and be free from any defects which might damage the road or endanger any person.

To be ‘fit for purpose’, tyres must not have:

• Any lumps, bumps or bulges, as these can mean structural damage.
• A cut or tear bigger than 25mm or 10% of the width of the tyre, whichever is greater, and which is deep enough to reach the ply or cord.
• Any part of the ply or cord exposed

The second requirement is that tyres must be inflated to the right pressure. That means sticking to the pressure recommended by both your vehicle manufacture and the tyre manufacturer.

What should my tyre pressure be?

Tyre pressure isn’t ‘one size fits all.’ Each car will have its own recommended pressures.

There's usually 2 figures quoted for each tyre size that might be fitted to the vehicle - the first is a normal tyre pressure and the other is a higher pressure given for heavier loads.

You can find these inside the driver’s door, inside your petrol cap or in the owner’s manual.

You'll fail an MOT if your tyres have any of these faults or if you have tyres of different sizes on the same axle.