Your tyres are the only part of your car that touches the road. Each contact patch is roughly the size of your hand, and it has to handle braking, steering and acceleration in all weathers. Tread is what keeps that grip working, especially when the road is wet. Checking your tyre tread depth takes five minutes, needs almost no equipment and could save you money, points on your licence and a lot of worry.

This guide explains the UK legal limit, three simple ways to measure tread at home and what to do when the numbers are not good.

What Is the Legal Tyre Tread Depth in the UK?

The legal minimum tyre tread depth for cars in the UK is 1.6mm. That depth must run across the central three-quarters of the tread and around the whole circumference of the tyre. Tread that is worn below this limit on any part of that band is illegal.

The penalty can be serious. Driving on illegal tyres can lead to a fine of up to £2,500 per tyre and three penalty points for each one. Worn tyres can also cause an MOT failure.

New car tyres usually start with around 8mm of tread. They wear gradually, so most drivers do not notice the change until it becomes a problem.

Why 1.6mm Is a Minimum, Not a Target

The legal limit is the point at which a tyre becomes unlawful, not the point at which it performs well. Grip, particularly on wet roads, falls as tread wears down, and stopping distances increase. Many tyre experts and motoring organisations suggest replacing tyres when tread reaches around 3mm. That gives you a safety margin rather than waiting for the last millimetre.

Three Ways to Measure Tyre Tread Depth at Home

You do not need a garage visit to check your tyres. These three methods all work on the driveway.

Method 1: The 20p Test

This is the quickest check, and it needs only a 20p coin.

1. Choose a main groove on the tyre.

2. Place the 20p coin into the groove with the edge facing outwards.

3. Look at the coin’s outer band. If the band is hidden by the tread, the depth is above 1.6mm.

4. If you can see the whole outer band, the tread may be at or below the legal limit and the tyre needs checking promptly.

Repeat the test at several points across the tyre and around its circumference. Wear is often uneven, so one good reading is not enough.

Method 2: A Tread Depth Gauge

A tread depth gauge gives you an exact reading in millimetres. Digital and analogue versions are cheap and widely available from motor shops and online.

1. Push the gauge pin into the groove until the base sits flat on the tread.

2. Read the measurement.

3. Take readings across the central three-quarters of the tyre and at several points around it.

A gauge is particularly useful if you want to monitor wear over time. A reading of 3mm or less is a good prompt to start planning a replacement.

Method 3: Tread Wear Indicators

Most car tyres have small raised bars moulded into the base of the main grooves. These bars sit at 1.6mm. When the surface of the tread becomes level with them, the tyre has reached the legal limit.

Look on the sidewall for a small triangle or the letters TWI. These mark where the indicator bars are. It is a handy visual check, though a gauge or coin gives you more detail.

What Else Should You Check While You Are There?

Tread depth is only part of tyre safety. While you are looking, spend another minute on these points.

Uneven Wear

If the inner or outer edge is more worn than the middle, something may be wrong. Worn centres can point to overinflation. Worn edges can point to underinflation or alignment problems. Uneven wear is worth showing to a professional, because the cause often needs correcting as well as the tyre.

Cuts, Bulges and Cracks

Run your eyes and hands carefully over the sidewalls and tread. Look for:

• Cuts or splits in the rubber

• Bulges or bubbles, which can signal internal damage

• Cracking in the sidewall, often from age

• Nails, screws or stones lodged in the tread

A bulge on the sidewall is a safety risk. Do not keep driving on it.

Tyre Pressure

Check pressure with a gauge when the tyres are cold. Your vehicle handbook or the sticker inside the driver’s door shows the correct figures. Under-inflated tyres wear faster, use more fuel and can overheat.

Tyre Age

Rubber ages even when a tyre is not used much. The four-digit code on the sidewall shows the week and year of manufacture. A tyre with plenty of tread can still be unsafe if it is very old, cracked or perished.

How Often Should You Check Your Tyres?

A good habit is to check pressure and tread about once a month, and before any long journey. Check more often if you:

• Drive on motorways or rough roads regularly

• Carry heavy loads

• Notice vibration, pulling to one side or a change in handling

• Have recently hit a pothole or kerb

It takes a few minutes, and a regular routine means you will spot changes early.

What to Do If Your Tread Depth Is Low

If your tyre tread depth is near 3mm, start planning a replacement. If it is at or close to 1.6mm, treat it as urgent. Driving on tyres at the legal limit is risky in wet weather, and tyres below it are illegal.

Here is a sensible approach:

1. Measure all four tyres. One tyre may be worse than the others.

2. Check the spare, if you have one.

3. Avoid long or fast journeys until you have sorted the problem.

4. Book a replacement as soon as you can rather than waiting until the next service.

For drivers who cannot easily get to a garage, a mobile service can be a practical choice. A company such as 24hrs Mobile Tyres Fitting can send a fitter to your home or workplace, so you do not have to drive on worn tyres to reach a workshop.

If a tyre has failed suddenly, perhaps through a blowout or sidewall damage, you may need emergency tyre replacement rather than a planned booking. In that situation, stop in a safe place and call for help instead of driving on.

Common Mistakes When Checking Tyre Tread

A few simple errors can give you a false sense of security:

• Measuring only one spot. Wear can vary across the tyre and around it.

• Ignoring the inner edge. This is hard to see from outside the car but often wears fastest.

• Treating 1.6mm as safe. It is the legal limit, not the point where performance is still good.

• Forgetting the spare. If you need it in an emergency, it should be roadworthy.

• Checking tread only. Pressure, cracks and age matter too.

Turning the steering wheel to full lock makes the inner edge easier to inspect.

Final Thoughts on Tyre Tread Depth

Checking your tyre tread depth is one of the simplest and most useful bits of car maintenance you can do. A 20p coin, a cheap gauge or a quick look at the wear indicators tells you whether your tyres are safe, legal and ready for wet roads.

Make it a monthly habit, check all four tyres and look beyond tread to pressure, damage and age. When the numbers drop towards 3mm, plan ahead. When they approach 1.6mm, act quickly. Good tyres are one of the most effective safety measures you can have on the road.