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What Is Legal Tyre Tread And Why Is It Important?

Tyres are a critical component of all cars, allowing journeys to happen safely. The dangers of illegal tyres that don’t meet minimum safety requirements are significant, with 968 motorists killed or injured in accidents caused by illegal, defective, or under-inflated tyres in 2013.

One aspect of tyre safety which is often overlooked but crucially important is tread depth. Having at least the minimum legal tread depth is important for ensuring a good grip on the road, especially in wet conditions. As a result, drivers with illegal tread depth could experience longer stopping distances, bad handling and risk of aquaplaning, as well as decreased fuel efficiency.

Legal tyre tread

UK law requires that tyres have a tread depth of no less than 1.6mm in a non-interrupted band covering at least 75 percent of each tyre. Tyres should be replaced before they reach this stage.

If you are caught driving with tyres below the legal tread limit, you could receive three penalty points and a £2,500 fine per tyre.

Risks of incorrect tyre tread

There is a range of associated risks that come with having tyre tread close to or beneath the legal limit, and all of them mean you’re putting yourself at risk on the road. Some of the main ones include:


One of the main purposes of tyre tread is to stop aquaplaning or hydroplaning from happening. Water on the surface of the road can decrease tyre grip, but with proper tread depth, the water won’t act as a barrier between your tyre and the road. Instead, it will escape through the grooves of the tyre.

Longer stopping distances

Proper tread depth doesn’t just prevent aquaplaning, it also helps to reduce stopping distances on both dry and wet roads. This is an important safety feature, as the shorter your stopping distance is, the less chance you have of being impacted by an incident ahead of you on the road.

Faster air pressure loss

Tyres with low tread depth also lose air pressure more quickly, making them even less safe on the roads. Even if you make a point to regularly check and adjust your tyre pressures if you have low tread depth you might find that they deflate again faster than you can keep up with.

How to check if a tyre is below the legal tread limit

There are many quick and easy ways to check if a tyre is below the legal tyre limit, but checks should be carried out regularly as a preventative method.

Many manufacturers include tread wear indicators in the tyre at the 1.6mm mark. If the surface of the tread rubber is level with the indicator, the tyre tread depth is close to the legal limit and should be replaced immediately.

You can also use a tyre tread depth 20p test to determine the tread of the tyre. Place a 20p coin into one of the grooves of your tyre. If the outer band of the 20p is visible, then your tyre may be below the legal limit. If you cannot see the outer band of the 20p, then your tyre tread depth is within the legal limit. You should ensure that you check each tyre.

Can a car fail its MOT because of tread depth?

The legal limit for tread depth is 1.6mm, so if your tread depth is under this your car will fail its MOT.  You may receive an advisory on your MOT if your tyres are under 3mm in tread depth, as they will need replacing soon before they begin to lose grip.

Your car can also fail its MOT if the tyres are damaged. This included nails in the tyre, punctures, bulges and cracks. This is due to the risk of a tyre blowout, and therefore your vehicle would be deemed unsafe until the tyres are replaced.

How long will a tyre last before running out of tread depth?

On average, a tyre will last for 20,000 miles, although this depends on driving style. Brand new tyres come with 8-9mm of tread depth, so you may be able to get more miles out of your tyres if you pick up a tyre with a deeper tread depth.

You can also make your tyres last longer by driving more conservatively. This will help prevent wheel spin and excessive use of the tyre rubber, in turn allowing you to complete more miles before the tread reaches the legal limit.

Should you change all your tyres at once?

If possible, you should have the same tyre make and compound on all of your tyres. This will help each wheel have equal performance, which will make the tyres last longer and also increase your safety whilst driving. It is important to ensure that the tyres on each axle are the same, as this will ensure the car drives smoothly and won’t pull to one side.

What are the causes of fast tyre wear?

There are many reasons why tyres could wear quickly, but simple changes to the way you drive can alter that. Often, tyres will wear quickly because of poor maintenance. For example, over- or under-inflated tyres can cause the tyre to wear faster because the weight isn’t evenly distributed. Incorrect wheel alignment or balancing of the wheels can also create bald spots in the tread. Even braking or accelerating quickly can cause uneven tyre wear.

If you are worried about your tyre tread, we provide a free tyre check at all of our Tyre Shopper fitting centres.

Our trained technicians will carry out a full inspection of your tyres to check their general condition and ensure the tyre tread meets legal requirements.

If you’d like to know more about correct tyre pressures, you can contact our experts for advice.

You may also be interested in the following article: How To Check Your Tyre Tread Depth helps show how you can use a 20-pence coin to check whether your tyres are legal for the road.



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