Whether you drive a car, caravan, motorbike or truck, proper tyre tread depth is essential for road safety – especially in adverse conditions.
Driving in the rain with worn tyres can heighten your risk of accidents. Braking distances and the risk of aquaplaning increase significantly under these conditions.
In this guide, we’ll explain what tyre tread depth is, how to measure it, when to check your tyres, and what the legal minimum tread depth for car tyres is in the UK.
Tyre tread depth summary
Here’s a quick overview of the key points about tyre tread depth and safety:
- The legal minimum tread depth for car tyres is 1.6mm
- Tyre and safety experts recommend replacing tyres at 3mm
- Use the 20p test or a tread depth gauge to measure tyre tread
- Check tyres monthly or before long trips
- Driving with worn tyres increases your risk of accidents and fines
What is “tyre tread?”
“Tyre tread” is the patterned part of the tyre that comes in contact with the road surface.It is made up of ribs, grooves, blocks and sipes which work to improve the tyre’s performance. Patterns and performance goals vary among manufacturers. But the primary function of the tread is to keep the tyre in contact with the road in wet weather by effectively displacing water.
What is “tread depth?”
Tread depth measures how deep the grooves in your tyre are. These grooves are essential because they:
- Keep your tyres gripping the road, even in wet or slippery conditions
- Channel water away to reduce the risk of aquaplaning
- Help your car brake, steer, and accelerate safely
The deeper the tyre tread, the more water it can clear from the road surface and the better its grip. As the tread wears down or water depth increases, grip is reduced. Drivers should take this into account and lower their speed in wet conditions.
Why is tread depth important?
Regularly checking tread depth is crucial because driving with worn tyres is dangerous and illegal.
Without enough tread, tyres may not be able to grip the road properly, especially in wet conditions. The grooves help to remove water from between the tyre and the road, allowing your car to brake, steer, and accelerate safely. As such, driving with a low tread depth can increase your risk of accidents. In tests carried out by MIRA , cars with 1.6mm tread had up to 44% longer braking distances in the wet than those with 3mm. It is therefore advisable to consider replacing your tyres well before they reach the legal tyre tread limit.
Plus, driving with tyres below the legal minimum tread depth can lead to fines of up to £2,500 and three penalty points PER tyre. Ideally, you should check your tyres every month.
How to measure tyre tread depth
The easiest way to check that your car tyre tread is above the minimum legal standard is to complete the 20p test by inserting a 20p into the tread grooves on the tyre.
If you can’t see the coin’s outer band, your tyres are above the legal limit. You can also use a tyre tread gauge, which is designed to measure individual tyre grooves.
Other methods include using a tread depth gauge or built in tread wear indicators.
| Method | How it works | Pros | Best for… |
|---|---|---|---|
| 20p test | Insert a 20p coin into tread grooves | Quick, no tools needed | Quick monthly checks |
| Tread depth gauge | Measures individual grooves in mm | Accurate measurement | Precise checking |
| Built-in tread wear indicators | Raised bars in grooves show wear | Very easy to spot | Spotting worn tyres |
Legal tyre tread depth limit in the UK
The legal tread depth minimum for cars, light vans and light trailers in the UK is 1.6mm.
The legal tread depth minimum for motorcycles, large vehicles and passenger-carrying vehicles in the UK is 1mm.
Your tyre should meet the legal minimum tread depth across three quarters of the centre of the tyre around its complete circumference.
What is the tyre tread minimum recommended by experts?
While the legal limit is 1.6mm, experts actually recommend that you have your tyres replaced sooner. You should have your tyre replaced once it reaches 2mm and the minimum tread depth commonly advised by tyre and safety experts is 3mm.
Waiting until the last minute to replace your tyre can prove risky as a significant amount of tread can be worn in just one emergency manoeuvre.
Did you know that the difference between illegal and borderline is just 0.4mm – that’s half the thickness of a bank card!
When should you check your tyres tread depth?
You should check your tyres at least once a month and before any long journeys.
Tread depth and aquaplaning
When driving on roads with significant standing water, vehicles can be vulnerable to ‘aquaplaning’.
Aquaplaning occurs when the water cannot be removed from between the tyre and the road. This causes the vehicle to lose all contact with the road, which effectively leaves the vehicle out of control. The risk of aquaplaning increases as a tyre’s tread depth is reduced as there is insufficient tread to clear the water properly from the road surface.
Lack of contact with the road means you are unable to accelerate or steer effectively, greatly increasing your risk of being involved in an accident.
It is also unsafe to try to brake when aquaplaning as contact with the road may be regained in an unpredictable manner, causing the vehicle to spin uncontrollably.
To reduce your risk of aquaplaning, it’s important to check your tyre tread and tyre pressure regularly.
Tyre Tread FAQs
Read the answers to commonly asked FAQs including how to check tyre tread and the impact of wet conditions on roads.
The legal minimum tread depth of cars in the UK is 1.6mm across a continuous band comprising the central three-quarters of the breadth of the tread and its entire circumference.
The easiest way to check that your car tyre tread is above the minimum legal standard is to complete the 20p test by inserting a 20p into the tread grooves on the tyre.
If you can’t see the coin’s outer band, your tyres are above the legal limit.
You can also use a tyre tread gauge, which is designed to measure individual tyre grooves.
Tyre treads are designed to give good grip on wet roads but in general wet grip decreases as the tyre tread depth approaches the legal minimum.
Motorists should take this into consideration and reduce speed when driving in wet conditions.
For the same reason, motorists may wish to consider replacing tyres before reaching the tyre tread limit.
New tyres generally have a tread depth of between 7-9 mm. But this will vary depending on the tyre brand, model and whether the tyre was designed for summer, winter or all-seaon use.
Generally, tyres with 3mm of tread depth may last between 10,000 and 20,000 miles. Actual lifespan can vary widely depending on factors like driving style, tyre type, road surface, and maintenance. Manufacturors do not provide mileage predictions for tread depth for this reason. It is recommended that tyres with 3mm tread depth are replaced as quickly as possible.
It is recommended that you change your tyre before it reaches this point but tyres with 2mm of tread depth may last ~1000 miles. Actual lifespan will vary widely depending driving style, tyre type, road surface, and maintenance. Manufacturors do not provide mileage predictions for tread depth for this reason.
There isn’t one! Both aquaplaning and hydroplaning refer to what happens when water builds up in front of your tyres and prevents them from making contact with the road. These terms are just synonyms of the same phenomenon.
Many winter tyres come with a deeper tread depth when new. Designed with specialised tread patterns and compounds, winter tyres are the safest option from October to March, when temperatures drop, and conditions become challenging. The minimum tread depth recommended for winter tyres is 4mm.
Tyres with 5mm of tread depth may last anywhere between 20,000 and 25,000 miles, but actual lifespan can vary widely depending on factors like driving style, tyre type, road surface, and maintenance. Manufacturors do not provide mileage predictions for tread depth for this reason.
