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How to check tyre tread depth

14th July 2021

Are you familiar with your car’s tyre tread depth? If you answered no, you’re not alone. A survey from Tyre Safe revealed that 1 in 5 drivers have never checked their tyres, so it’s no surprise that there are roughly 10 million illegal tyres on Britain’s roads every year.

Tyres are a vehicle’s only point of contact with the road and if they don’t have adequate grip, the consequences can be fatal. In 2018, 17 people were killed and 116 people were seriously injured in road traffic accidents where illegal, defective or under-inflated tyres were deemed to be a contributory factor to the accident, according to Road Safety Factsheet from RoSPA.

These accidents are preventable by monitoring your tyres more closely, which takes just minutes. You don’t even need any technical equipment – just a twenty pence piece (but more on that later!) From the legal minimum tread depth to how often you should check your tyres, find everything you need to know in our detailed guide.

Why tyre tread matters

Tyres with sufficient tread depth are able to maintain contact with the road and this grip increases road holding and driver control. This is crucial when driving in wet weather conditions where you run a greater risk of losing control of the car.

Whether you’re driving in a built-up town centre or residential setting, or at high speed on the motorway, insufficient tyre tread can lead to additional expenses and in extreme cases, catastrophic injuries.

If you are found driving on tyres that have tread lower than the legal minimum, you can receive up to three penalty points on your driving licence and a fine of £2,500 per illegal tyre. That’s a whopping £10,000 for all four tyres, which can easily be avoided if you make a habit of checking your tyre tread depth.

What is tyre tread depth?

A tyre’s tread is made up of the little grooves and ridges that run along the circumference of a tyre’s rubber surface. Each one of these grooves offers grip to the road’s surface, allowing drivers to brake and manoeuvre safely.

In wet weather conditions, your tyre’s tread works hard to clear water away from the tyre. To put this into perspective, when there’s heavy rain, each tyre can shift one gallon of water every second.

The Highway Code advises that in wet weather conditions, your total stopping distance will be at least double the distance to stop on a dry road. To learn more about the differences in stopping distances on wet roads, read our helpful guide about why tyre tread is so important.

Legal minimum tyre tread depth

A tyre starts its life with approximately 8mm of tread, which will wear away over time. Although the legal minimum tyre tread depth in the UK is 1.6mm across the central ¾ of the tyre width, many road safety organisations, and tyre experts, like Merityre, recommend that your tyres have a minimum tyre tread depth of 3 mm. This is because below 3mm, the tyre’s gripping and handling capabilities are drastically reduced, braking distances increase and your resistance against aquaplaning is significantly weakened.

How do I measure my tyre tread?

The quickest and easiest way to check your car’s tyre tread depth is by conducting the ‘20p test’. This is where you place the flat edge of a twenty pence piece into the tread grooves across your tyre. To get an accurate result, it's important to carry out this test on at least three locations around each tyre.

If you can't see the outer band on the coin inside the groove, your tyres are above the legal limit. However, if any part of the outer band of the coin is visible above the tread, then your tyres are illegal and must be replaced immediately by a qualified tyre professional.

Alternatively, you can purchase a tyre tread depth gauge which will quickly measure the depth of an individual tyre groove.

How often should I check my tyre tread depth?

By regularly checking the tread on all four of your tyres, you can diagnose potential problems and prevent delays, additional expense and dangerous cases of injury. It’s recommended that drivers check their tyre tread depth once every two weeks or at the very least, once a month. You should also check them before and after long journeys.

When should I replace my tyres?

The roadworthiness of a tyre depends on a number of factors, from the condition in which they are stored, and the use to which they are put, to road conditions, how well tyres are maintained and the driver’s driving style. While there is no universal recommendation about the age of tyres, you can get an idea for your vehicle by asking your car manufacturer when they should be changed. Another thing that helps is looking out for age-related defects to your tyres, such as:

  • Cracking/grazing on the side wall of the tyre, caused by it flexing
  • Distortion of tyre tread
  • Deformation of the carcass of the tyre

Tyres that show these signs of ageing are no longer fit for purpose and should be replaced. If you’re in any doubt about the quality of your tyres, take a look at our comprehensive Tyre Safety section.

Here at Merityre Specialists, we provide a wide range of new tyres to buy online. Simply locate your nearest branch and book in for your tyre fitting today.