Tyre tread depth, UK law and tyre safety checks

The tyres are the only contact point between your vehicle and the road. If your tyres are past their best then the safety of your vehicle will be compromised. 

Driving a car with bald tyres can risk a fine of £2,500 and three penalty points. That’s per tyre, too. If all four tyres are worn below the legal limit, you could potentially be summoned to court, lose your licence and face a £10,000 fine.

Read on to find out how to check your minimum tyre tread depth and ensure you stay safe and legal on the road. 

The legal tyre tread depth limit for cars in the UK and Europe is 1.6mm across the central three-quarters of the tyre. By law, the tread depth must meet this minimum requirement across its complete circumference. 

Bald tyres are one of the most common reasons for MOT fails, which is why it's essential that you get into the habit of checking your car's tyres regularly. 

If you are not confident checking your car's tyres yourself, you can arrange for it to be checked by a mobile mechanic or local garage. 

Tyre and safety experts believe the 1.6mm legal minimum is insufficient to guarantee safety – most recommend a minimum tread depth of 3mm for tyre replacement.

Tests by UK technical organisation MIRA found that, once tyres are below 3mm, stopping distances increase dramatically.

The difference in wet braking distance between a tyre worn to 3mm and one worn to 1.6mm can be as much as 44%. 

Worn tyres are particularly dangerous in the wet because a tyre’s tread helps disperse water away from the contact patch between tyre and road.

If there’s less tread depth, less water can be shifted, increasing the risk of aquaplaning and losing grip.

In heavy rain, each tyre can shift one gallon of water every second, illustrating just how hard tyres work.

Simply put, deeper tread means they can work better, improving grip. 

• Should I buy winter tyres? Pros, cons and costs explained
• A guide to run flat tyres - do you need them?
• What makes your tyres illegal?

Tyre tread depth of your car must to be above 1.6mm to be safe and legal. The 1.6 minimum tyre tread depth must be the case for the middle three quarters of the tyre.

If you are unsure if the tyres on your car meet the legal minimum standard then there are three simple methods you can use to check the tread depth:

• Perform the 20p test
• Inspect the wear indicators on the tyre (if fitted)
• Check the tyre tread with a depth gauge

The 20p test is a simple, quick and easy way of checking the tyre tread of your car's wheels. 

Just take a 20p coin and insert it into the tread grooves on the tyre.

If you can't see the outer band on the coin, your tyres are above the legal limit.

However, if you can see the band and that section of the coin is still visible, your tyres could be unsafe and require professional inspection by a mechanic.

We suggest drivers conduct the 20p test around every two weeks and before long journeys.

Checking tyre tread with tyre tread wear indicators

Some tyres will have indicators embossed on the tyre wall itself, usually with a line or arrow which is positioned somewhere below the outer tread.

If the tyre is flush with these markers then the tread may be at or below the 1.6mm legal limit and will need replacing.

Checking tyre tread with a tyre tread depth gauge

A tyre tread depth gauge is a purpose made tool that makes it easy to quickly measure the depth of an individual tyre groove. Simply place the tool on the tyre and it will tell you what the depth of your tyre is in millimetres.

Analogue tyre tread depth gauges (pictured above) are common, but digital gauges are also popular. Both tools make it easy to check your tyres are safe and legal.

READ MORE: How to check your car's tyre pressure

Driving with tyres that have a tread below the legal limit - or even worse, are bald - is dangerous.

It can put you and other motorists at risk.

If you are involved in an accident and the car you are driving has illegal or bald tyres, you should be aware of the consequences.

Any insurance claim as a result of an accident could be invalidated, so potentially your insurer won't pay out any money any repairs needed to your vehicle.

However, driving with dangerous or defective tyres also puts drivers at risk of a fine of up to £2,500 and three points on their license.

That is per tyre, so four illegal tyres could mean a fine of £10,000 and 12 penalty points.

You can buy tyre tread gauges that help you assess the tread depth of the tyre, plus you can also get more basic colour-coded tools that let you know if a tyre is legal or not at a glance.

For more information about tyres read our complete guide to tyre buying or our complete guide to tyre safety and maintenance.

For complete piece of mind, you can also check out our breakdown cover and European breakdown cover products today.

ALSO: Learner driver insurance - from 2 hours to 5 months

If your tyre tread is below or neat the legal limit, we would recommend that you purchase a replacement tyre. Head over to RAC Tyres where we sell everything from budget to premium brands.