3 Ways To Check Tyre Tread Depth: Every Driver Should Know

Often, drivers take their tyres for granted until the vehicle fails to respond or exhibits some other unusual behaviour. The depth of tread on your tyres affects your chances of being in an accident as much as your car's engine or other mechanical components.

They are the only component of your car that touches the ground when operating. If the tread of your tyre has become too thin, it will not provide adequate grip, traction, or control while braking.

At Advance Motors, we see worn tyres more often than almost any other issue during routine inspections. Drivers, even customers, often do not know that their tyres' tread is too thin or right at the minimum legal requirement until we show them during an inspection. The reason is simple; many drivers only take a brief look at their tyre tread when they fill up with fuel.

This guide will explain the importance of tyre tread depth, highlight the potential dangers associated with driving on tyres with tread below legal specifications, and teach you how to perform a tyre tread check in your driveway.

The Importance of Tread Depth on Tyres

When you drive a vehicle, you are not simply driving forward. The tread of the tyre keeps the car from skidding when turning corners; channels water away from the tread when driving on wet surfaces; stabilises the car when the tyres are used for braking; and ensures the vehicle always has adequate grip, regardless of the conditions in which the car is being driven.

The inability of tyres to provide adequate grip is directly related to the surface area of the tyre that is in contact with the ground at any given time.

Here’s what happens as tread wears down:

• Your stopping distance increases, and not by a small amount.
• Water cannot clear fast enough, making aquaplaning more likely.
• Grip reduces during acceleration and cornering.
• Braking becomes unpredictable in the rain.

We often remind customers that even though the legal minimum for tyre tread depth is 1.6mm, the decline in safety begins well before that point. Most tyre specialists – and most dealerships, including “we” – recommend replacing tyres at 3mm, because the difference between 3mm and 1.6mm is far bigger than it sounds.

One set of tests conducted in the UK showed that braking distances on wet roads can increase by up to 44% once tyres drop from 3mm to the legal minimum. When you picture an emergency on a motorway or at a busy junction, that extra distance becomes very real.

What Is the Legal Tyre Tread Depth in the UK?

For cars in the UK and Europe, the law requires 1.6mm of tread across the central three-quarters of the tyre’s width. This 1.6mm must be consistent around the entire circumference of the tyre.

Anything less and the tyre is illegal.

Driving with illegal tyres carries some of the toughest penalties for everyday motoring:

• Up to £2,500 fine per tyre
• 3 penalty points per tyre
• Risk of losing your licence if multiple tyres fail
• Insurance claims can be refused after an accident

People are often surprised to learn it’s “per tyre”. Four bald tyres could technically lead to £10,000 in fines and 12 points. In more serious cases, the driver may even be required to appear in court.

This is why tyre tread depth checks are so important. A quick look is not enough. You need to know how to do a proper tyre tread depth check using the correct methods.

Is the Legal Limit Enough to Keep You Safe?

Legally, yes. Practically, not always.

Tyre experts generally recommend replacing tyres when the tread reaches 3mm, even though 1.6mm remains the minimum. Once the tread depth drops below 3mm, several things happen:

• Water cannot clear fast enough beneath the tyre
• Wet braking distances jump sharply
• The tyre struggles to maintain grip during emergency manoeuvres
• Aquaplaning becomes significantly more likely at motorway speeds

In heavy rain, each tyre can move roughly a gallon of water every second. As tread reduces, that ability drops. You don’t feel it immediately, but the moment you brake hard or hit standing water, it becomes obvious.

This is where having a consistent tyre tread depth check routine helps you stay ahead of any issues.

The 3 Most Reliable Ways To Check Tyre Tread Depth

Now let’s get into the heart of the guide. There are three easy, everyday methods that any driver can use. These are the types of tyre tread depth check commonly used by technicians and recommended by most UK motoring organisations.

1. The 20p Test: The Quick Everyday Check

This is the simplest method and the one we recommend for regular home checks. You only need a standard 20p coin, nothing else.

Here’s how to do it:

• Insert the 20p coin into the main grooves of your tyre.
• Look at the outer band around the edge of the coin.
• If you cannot see the outer band, your tread is above 1.6mm.
• If the band is visible, your tread may be below the legal limit, and you should get the tyres checked professionally.

This method isn’t precise, but it is brilliant as a fast tyre tread depth check and helps you keep an eye on wear every few weeks. We advise customers to perform the 20p test every fortnight or before a long journey.

2. Tyre Tread Wear Indicators: Built-In Safety Markers

Most tyres have wear indicators moulded into the grooves. These are small rubber bars set at 1.6mm. When the tyre tread becomes level with these bars, it signals the tyre has reached the legal minimum.

Where to find them:

• Look for small raised blocks in the grooves.
• Some tyres also have small symbols (like triangles or TWI markings) on the sidewall pointing to where the indicators are located.

This is one of the more risk-free types of tyre tread depth check because the indicators are consistent and easy to spot once you know where to look.

However, drivers often overlook them because they are subtle. During services at Advance Motors, we often show customers the exact spots so they can identify them more easily in the future.

If the tread is flush with the indicator, that tyre needs replacing immediately.

3. Using a Tyre Tread Depth Gauge: The Most Accurate Method

A tread depth gauge is the most reliable and precise way to check tyre tread depth. These tools measure the depth in millimetres, giving you a clear reading.

There are two types of tread depth gauge:

• Analogue gauges (simple, mechanical, easy to use)
• Digital gauges (small screens, fast readings, affordable)

So, how do you use them? First, place the gauge flat on the tyre surface. Then, press the measuring probe into the groove. Read the depth displayed. Repeat in several spots around the tyre to ensure accuracy.

This is the type of tyre tread depth check used by most technicians because it removes guesswork and highlights uneven wear patterns. If you want to monitor tyre wear more carefully, a gauge is a very handy tool to have at home.

At Advance Motors, we also use these gauges during inspections and record the measurements during car servicing.

How to Know Your Tyres Need Replacing Before You Reach the Minimum

Even if you pass a tyre tread depth check at 2mm or 3mm, certain warning signs mean replacement should not be delayed.

Look out for:

• Inside or outside shoulder wear
• Feathering (rough edges along the tread blocks)
• Cracks along the sidewall
• Visible cords or exposed rubber
• Vibration at certain speeds
• Tyres wearing unevenly across axles

These signs often indicate alignment problems, low tyre pressure, suspension issues, or simply a tyre nearing the end of its safe working life.

What Happens If You Drive With Illegal or Bald Tyres?

This is where many drivers get caught out. If you have an accident and an investigation finds your tread below 1.6mm:

• Your insurance may refuse the claim
• You may be held legally liable for damages
• You face fines of up to £2,500 per tyre
• You receive 3 penalty points per tyre
• Your driving licence could be at risk

We’ve had customers who were genuinely shocked to learn their tyres had become illegal without them realising. Tyres tend to wear gradually, so unless you perform regular tyre tread depth checks, it’s easy to miss the moment they dip below the limit.

Why Some Tyres Wear Faster Than Others

If you feel like your tyres wear out quicker than expected, there are several common reasons:

• Driving with incorrect tyre pressure
• Poor wheel alignment
• Cheap tyre compounds
• Hard cornering or aggressive braking
• Driving with an overly loaded vehicle
• Hitting potholes or kerbs frequently

Each one of the above reasons can affect tyre tread depth and cause uneven wear. This is why tyre maintenance is just as important as checking the tread.

How to Make Your Tyres Last Longer

A few small habits make a noticeable difference:

• Check tyre pressure monthly
• Rotate tyres every 6,000 - 8,000 miles
• Replace tyres in pairs
• Avoid kerb scrapes
• Get alignment checked annually
• Inspect tyres after long trips

Regular tyre tread depth checks, especially the quick 20p test, help you catch wear before it becomes a problem.

When Should You See a Mechanic?

You should book a professional inspection if:

• The 20p test shows visible banding
• The wear indicator is flush with the tread
• Your gauge reads 2mm or lower
• You see cracking, bulges or uneven wear
• The car pulls to one side
• You feel vibration through the steering

At Advance Motors, we offer tyre inspections, replacements and alignment checks. Many customers appreciate having a trained eye look over the tyres because it’s difficult to judge condition without the proper tools.

A technician can also identify hidden issues like misalignment or suspension wear that contribute to rapid tyre wear.

Final Thoughts

Tyre tread depth might seem like a small detail, but it plays a huge part in your safety on the road. A tyre tread depth check takes less than a minute, and understanding the types of tyre tread depth checks available means you can stay ahead of dangerous wear.

Whether you use the 20p coin, the built-in wear indicators, or a proper depth gauge, each method helps keep your car legal and safe. If you are ever unsure, bring your car to Advance Motors. Our team checks tyre tread depth during routine service, during MOT preparation, and whenever you pop in for a quick inspection.