‘Tyre tread’ refers to the rubber on the circumference of the tyre that makes direct contact with the ground. Over time, the tyre tread wears away which limits its effectiveness. A set of new tyres on a new car will have a tread of around 8mm, however, the rubber will wear down over time. Overly worn tyres can be very dangerous, as they will not provide you with full control over your vehicle whilst driving, especially when braking in wet conditions. The risk is even worse when driving with bald tyres (where the tread has worn away altogether).
The law states that all drivers must ensure that their tyres have the correct tyre tread depth, so it’s important to perform regular checks to ensure you’re within the legal requirements. Having a good tread depth gauge is also imperative to your safety. Remember, your tyres are the only part of your car that’s actually in contact with the road, so their condition is essential to your safety.
In this article, we explain exactly what the legal limit on tyre tread depth is, how to check your tread depth and what to do if you’re not within the legal minimum tread depth. Hopefully, this article will answer all the questions you have about checking your tyres.
Why Is Tyre Tread Depth Important?
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It’s a legal requirement
In the UK, it’s a legal requirement to have tyres with a tread depth of at least 1.6mm. If you are caught driving with illegal tyres, you risk being fined up to £2,500 and getting three penalty points on your driver’s licence. Remember, this fine is per tyre too!
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Minimises stopping distance
The stopping distance is the time that it takes for the driver to notice a hazard (thinking distance) and the time it takes for the car to fully stop after breaking (braking distance). Tyres with an effective grip can significantly reduce your stopping distance. This is very important for helping you to maintain control of your vehicle but is crucial for when you need to perform an emergency braking manoeuvre. According to a study performed by the MIRA, tyres at the minimum tread depth of 1.6mm increase your stopping distance by 36.8% on hot-rolled asphalt and by 44.6% on smooth concrete.
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Reduces risk of aquaplaning
Without the correct tread depth, your car tyres may not be able to perform safely in wet conditions. In wet weather, your tyre tread grooves help to remove water from between your tyres and the road surface helping you to brake, steer and accelerate.
Aquaplaning occurs when a layer of water builds up between a vehicle’s tyres and the surface of the road beneath, leading to a loss of traction that prevents the vehicle from responding to control inputs by the driver. It can be very dangerous and scary for a driver to experience. The risk of aquaplaning increases for tyres with low tread depth, because the tread of tyres is carefully designed to help disperse water.
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For your car insurance
Driving with illegal tyres can also cause your insurance premiums to rise. If your tyres are below the legal tread depth or are structurally unsafe, it could invalidate your insurance premium and make it difficult for you to make insurance claims in the future.
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Increases chance of punctures
Driving with low tyre tread increases your chance of getting punctures, which can lead to a sudden blowout.
What Causes Wear to Tyres?
The depth of new tyres is around 8mm, but over time this will reduce as the tyres get worn down. Whilst the typical lifespan of tyres will vary from vehicle to vehicle, there are some factors that will affect how quickly the tread is reduced. These include:
- Your driving style
- The quality of tyres
- Overloading your vehicle
- Improper tyre pressure
- Improper tyre alignment
- Faulty suspension
- Worn steering system
If you are concerned that there might be some issues with your vehicle causing wear to your tyres, then you should book an appointment at your local garage where you can get professional tyre servicing.
What is the Legal Tyre Tread Depth?
By law, motorists in the UK are required to have a tyre tread depth of at least 1.6mm. Remember, this means having a tyre tread of 1.6mm in a continuous band around the central three-quarters of the tyre, not just in one place. This rule applies to all cars as well as goods vehicles, such as vans, trailers and caravans that don’t exceed 3500kg.
Failing to keep your tyre depth in the legal limit of 1.6mm could result in:
- A fine of £2,500 per tyre
- Three points on your licence per tyre
- Your car insurance premiums to rise
How to Perform a Tyre Tread Depth Check
When testing your tread depth check, make sure to take multiple measurements across the central three-quarters of the tyre, since cornering and alignment can cause tyre tread to wear at different rates across the whole tyre.
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Using a tyre tread depth gauge
Tread Depth gauges are an easy to use tool made to quickly measure the depth of an individual tyre groove. To do this, you simply place the gauge on the surface of the tyre and push the end down into one of the tyre grooves to get the depth reading.
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The 20p test
This simple test is a quick and easy way to measure tyre tread depth using a 20p coin. This is because the border around the outside edge of a 20 pence piece is approximately 1.6mm. Place the 20p coin into the main tread grooves of your tyre. If your tyres are the legal tread depth, then you should not be able to see the outer band of the coin. If you can see the outer border of the coin, then it’s very likely that your car tyres are approaching the legal minimum tread depth or has already reached it and needs to be replaced.
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Tyre tread wear indicators
The tyre tread wear indicators (TWIs) are markings spaced evenly through the main grooves in the tyre tread pattern, to indicate how much of the tyre has already rubbed off. Their purpose is to help drivers know if the tyre is worn out and needs replacing. If the wear indicator is even with the level of the tread, then the tyre should be replaced.
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Book into your local garage
If you are not confident in measuring your tyre tread depth from home, then book in your local garage for a tyre check. A professional mechanic will be able to give you an accurate measurement and advise you of when your tyres need replacing.
How Often Should I Check My Tyre Tread?
It’s recommended that you check the quality of your tyres at least once a month, which includes measuring both the tyre tread and the tyre pressure. Tyres can lose up to two pounds of air per month and they can quickly become underinflated if this goes unchecked. Make sure to always check your tyre tread and pressure before making any long journeys, especially in adverse conditions.
Other Legal Tyre Requirements
Because your tyres are so important to your safety whilst on the road, there are some legal requirements that you need to meet before heading out on journeys. As well as having the correct tread, your tyres should also:
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Be ‘fit for purpose’
This means that your tyres should fit the purpose of your vehicle. When getting new tyres, they must be the correct size, and have the correct load index and speed rating for your vehicle. All of this information can be found on the sidewall of your tyre. All of your tyres must also be compatible with one another too.
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Inflated to the right pressure
This means that your tyres must be inflated to the pressure recommended by both your vehicle manufacturer and the tyre manufacturer.
What Should My Tyre Pressure Be?
You can find the recommended tyre pressure for your vehicle in your vehicle handbook. It might also be printed in the sill of the driver’s door or on the inside of the fuel tank flap. Remember to always check your tyre pressure when your tyres are cold using a tyre pressure gauge. If you are using your vehicle to carry additional load or weight, consult your vehicle handbook for the correct loaded tyre pressure.
Sources:
https://www.rospa.com/rospaweb/docs/advice-services/road-safety/vehicles/tyre-tread-depth.pdf