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Tyre tread depth is one of the most important legal and safety requirements for driving in the UK. Driving on tyres below the legal minimum tread depth is illegal, dangerous, and can invalidate your insurance.
For car tyres, the current UK law states that the minimum tread depth is 1.6mm across 75% of the tyre’s circumference and across the central three-quarters of the tread.
If any tyre falls below the legal limit, it is considered illegal – even if the other tyres are compliant.
Tyre tread is the part of the tyre that comes into contact with the road surface. The tread pattern is designed to provide grip, channel water away, and maintain stability during braking and cornering.
As tread wears down, a tyre’s ability to perform safely is reduced – particularly in wet or slippery conditions.
The legal minimum tyre tread depth is one of the most common reasons tyres fail MOTs and roadside inspections. It applies across most vehicle types and must be met at all times when driving on public roads.
Car tyres
1.6mm across 75% of the tyre’s circumference and across the central three-quarters of the tread
Motorcycle tyres
1.0mm across the full tread width, provided the original tread pattern did not extend beyond three-quarters of the tyre width when new
Van tyres
1.6mm minimum tread depth
Caravan tyres
1.6mm across three-quarters of the tyre’s circumference
4x4 tyres
1.6mm minimum tread depth
SUV tyres
1.6mm minimum tread depth
Trailer tyres
1.6mm minimum tread depth
Truck tyres
1.0mm in a continuous band across the central three-quarters of the tread width, around the full circumference
There are two main ways to check your tyre tread depth:
Checking your tyres regularly helps you spot wear early and stay safe and legal on the road.
The 20p coin test is a quick and simple way to estimate tread depth.
To do this, place a 20p coin into the main grooves of the tyre. If you can see the outer band of the coin, the tyre may be below the legal limit.
It is always advisable to check several points around the tyre’s circumference.
If the tyre appears close to or below the limit, it should be checked by a qualified mechanic.
10p coin
Older guidance suggested using a 10p coin, but since the design changed in 2013, it no longer features the outer dots used for measurement. Because of this, it is no longer a reliable test.
50p coin
Although sometimes suggested, the 50p coin is too large and unevenly shaped to provide an accurate tread depth check.
The 20p coin remains the most suitable coin-based test.
A tyre tread depth gauge provides the most accurate measurement.
To use one, insert the gauge probe into the tyre grooves, press until it reaches the base of the tread, and read the measurement in millimetres.
These gauges are inexpensive, easy to use, and give an exact reading of your remaining tread depth.
To test your car tyres, take your gauge and insert the depth finder between the grooves. The gauge should provide a readout showing exactly how much tread remains.
Yes. Even if your tyre meets the legal minimum tread depth, it can still be illegal if it is damaged, cracked, or perished.
Under UK law, it is illegal to drive a vehicle if a tyre’s ply cords are exposed. While not all cracked tyres immediately expose the cords, cracks can quickly worsen – meaning you may already be committing an offence without realising it.
If caught driving on illegal tyres, you could face:
Because cracks can spread and deepen over time, any visible cracking should be treated seriously. Regular visual inspections help catch problems early and reduce the risk of driving illegally.
Yes – cracks in tyre tread or sidewalls are dangerous.
Cracks weaken the tyre’s structure, making it more vulnerable to:
Once cracks appear, the rubber has already begun to deteriorate. Even if the tyre looks usable at first glance, its ability to perform safely is compromised.
Yes – perished tyres are illegal in the UK.
A perished tyre is one that has deteriorated due to age and environmental exposure. This typically appears as cracking or fissures in the tread or sidewall. Once a tyre has perished, its strength and structural integrity are compromised.
Common causes of tyre perish include:
Because perished tyres significantly increase the risk of failure and accidents, they are considered unsafe for road use.
If caught driving on tyres below the legal tread depth or with dangerous damage, you could receive:
Beyond the legal consequences, worn tyres severely reduce braking performance, handling, and stability – increasing the risk of accidents.
Yes. Driving on tyres below the legal tread depth can invalidate your insurance.
If you’re involved in an accident and your tyres are found to be illegal or unsafe, insurers may refuse to pay out for:
Keeping your tyres legal and well maintained protects both your safety and your insurance cover.
Regular tyre inspections help you:
If you notice cracking, uneven wear, or low tread depth, have your tyres checked by a professional and replaced if necessary.