It’s important to routinely check your car’s tyres and ensure their tread depths are safe and legal. After all, the tyres are the only point of contact between the car and the road. So, any tyres that are severely worn will compromise the safety of your vehicle.
What’s more, if the police catch you driving with bald tyres, you risk incurring a fine of up to £2,500 per tyre and three penalty points on your licence. If all four tyres are worn past the legal limit, you could lose your licence and face a potential fine of £10,000.
In this guide, we will explain how to check your tyre tread depth to stay safe - and avoid getting caught out.
We’ll also cover the other signs that indicate tyres are in need of replacement, how worn and damaged tyres can impact vehicle performance – and the steps you can take to prolong your tyres’ lifespan.
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What is the legal tyre tread depth?
In the UK and Europe, the minimum legal tyre tread depth is 1.6mm across the central three-quarters of each tyre. To be classed as road legal, tyres must meet the minimum tread depth requirement across their entire circumference.
Tyre condition and tread depth are both points of inspection on the MOT checklist. If you have one or more bald tyres, you will automatically fail your MOT. Therefore, it’s well worth checking them before taking your motor for its MOT.
You can check your tyres quickly and easily at home. However, you can also have them checked by a mechanic if you prefer.
Should you run a tyre to the legal limit?
No, we recommend replacing your tyres well before they wear down to the legal limit. When your tyres are close to worn, this can compromise the safety of your vehicle and affect its handling, especially in inclement weather.
When should I replace my tyres?
Many mechanics believe the legal minimum tread depth of 1.6mm is not enough for a car to handle safely. Replacing your tyres before they wear down to 3mm is widely recommended.
How can worn tyres affect stopping distance?
Tests conducted by UK-based technical organisation MIRA, have shown that once tyres are worn below 3mm, stopping distances significantly increase.
In fact, the difference in wet braking distance between a tyre worn to 3mm and one worn all the way to 1.6mm can be as much as 44%.
Worn tyres are especially dangerous in wet conditions, because the tread depth of a tyre disperses water from the contact patch between the tyre and the road. When there is less tread depth, less water can be cleared, which increases the risk of aquaplaning and loss of grip.
In heavy rainfall, a tyre can shift a full gallon of water in a second, which demonstrates the importance of sufficient tyre tread depth.
How to check tyre tread depth
In this section, we’ll cover three simple methods for checking your car’s tyre tread depth.
Whichever method you choose, remember to repeat the test every two weeks and before any long journeys to ensure your tyres are safe and legal.
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The 20p test
This is the fastest and easiest way to check your tyres’ pressure – and all you need is a 20p coin.
Simply insert the coin into the tread grooves on each tyre. If you can’t see the outer band on the coin, the tread is above the legal minimum.
However, if the outer band is visible, your tyres could be worn past the legal limit, so you should take your car to a professional mechanic for inspection.
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Check the tread wear indicators
Some tyre models have indicators embossed into the tyre wall (usually with a line or arrow placed below the outer tread). If the tyre is flush with these indicators, this means it is below the legal limit and should be replaced.
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Checking with a tyre tread depth gauge
A tyre tread depth gauge is specifically designed to measure the depth of tyre grooves. To measure your tyre tread depth:
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Extend the measuring probe.
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Place the probe into the groove.
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Push down on the base.
If the measurement is below 1.6mm, replace the tyres immediately. You should also replace the tyres as soon as possible if there is less than 3mm of tread remaining.
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Why do tyres have a tread pattern?
Symmetrical tyre tread patterns provide a smoother drive, less rolling resistance and improved directional stability.
Furthermore, tyres with directional tread patterns also protect against aquaplaning, handle well in snowy and muddy conditions – and hold the road well at higher speeds.
The impact of tyre condition on vehicle performance
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Worn tyres have higher stopping distances than those with good tread levels. This increases the risk of accidents, especially in inclement weather.
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Reduced tyre pressure increases fuel consumption.
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Even budget tyres have been tested to meet stringent safety standards and will provide a safe, reliable drive when kept in good condition.
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All tyres fitted to a car should be of the same size and tread, even if the brands are not the same. If tyres of differing sizes are fitted to the same axle, this will lead to MOT failure, as this mismatch will affect the vehicle’s safety and performance.
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If one of your tyres gets a puncture, your car’s handling and safety will also be compromised, so you should replace it promptly.
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It is also important to factor in the age of your tyres. Many mechanics recommend replacing your tyres every 7-10 years.
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Aging tyres may be damaged from exposure to rain, sunlight and heat. They may also develop cracks. if you notice cracks in a tyre, ask your mechanic to inspect it.
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Tyres that are five years old or more should be checked more regularly.
Recommendations for minimum tread depth by safety experts
Although the legal minimum tread depth is 1.6mm, many safety experts recommend replacing tyres before they reach a tread depth of around 3mm.
Tyres that are worn beyond 3mm and nearing the legal limit will have longer stopping distances and increased risk of aquaplaning compared to those with a safer tread level. Their responsiveness and control in an emergency stop situation will also be reduced.
Your tyre tread depth could make the difference between being involved in a serious collision – and narrowly avoiding one.
Tyre maintenance tips to extend lifespan
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Regularly check your tyre pressure and ensure your tyres are properly inflated.
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Keeping heavy items in the boot will weigh the car down, increasing wear on the tyres. Remove anything you don’t need before each journey.
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Tyres wear at slightly different rates, depending on where they are fitted. Rotating your tyres at 5,000-mile intervals (from left to right, back to front and diagonally) can help them to wear more evenly. You can do this yourself or take your car to a mechanic.
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Avoid aggressive driving; slowly accelerate up to speed and reduce your speed in good time.
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Having your wheels aligned every 2-3 years can reduce tyre wear.
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Potholes, kerbs and other hazards can put your wheels out of alignment.
When to consider tyre replacement beyond tread wear
Whilst tread wear is often the reason a tyre will need to be replaced, there are other signs to watch out for:
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Bulges and blisters on the tyres.
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Tyre punctures.
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Vibrations and strange noises from the tyres.
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Cracks and damage on a tyre’s sidewall. (This can indicate a potential blowout, so you should take your car to a mechanic as soon as possible.)
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Your tyres are 5-10 years old. Older tyres should be monitored regularly and replaced promptly once they are too worn or damaged for safe use.
Tyres and MOT checks
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Tyre type and size: The inspector will check that the tyres fitted are of the correct size, load and speed rating for your vehicle. Unsuitable tyres will affect your car’s safety and performance.
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Tyre tread depth: The tread depth must be above the legal minimum of 1.6mm on all tyres. If it is not, you will fail your MOT, as the tread provides the grip and traction needed to control your car.
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Tyre pressure: Low tyre pressure can cause your tyres to wear out quickly, whilst compromising handling, stability and fuel efficiency.
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Tyre condition: The inspector will check the tyres for, cuts, bulges and damage. If there are any defects found, they will recommend tyre replacement.
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Tyre alignment: If the tyres are not correctly aligned, this can cause uneven wear, which can also compromise the car’s handling and safety. The inspector may recommend alignment correction if needed.
Don’t forget to regularly check your tyre pressure and tread depth. Watching out for any wear and tear can help to ensure your tyres don’t let you down at your next MOT.