Skip advert
Advertisement

Tyre tread depths explained: the legal limit and what it means for you

Bald tyres aren’t only dangerous but they’re also illegal. Here’s everything you need to know about tyre treads

Peugeot 308 SW - tyre

Making sure your car’s tyres have enough tread depth is one of the simplest and most important DIY car checks you can carry out. It can save you money through reduced wear and improved fuel economy, and it can save your life in an emergency situation. Read on for our guide to tyre tread depth. 

What is tyre tread depth?

Tyre tread depth is the difference in height between the main surface of the tyre and the raised blocks that make up the tread pattern. The minimum legal tread depth in the UK is 1.6mm, so the raised blocks must sit at least this height proud of the base rubber of the tyre.

Sufficient tread depth is needed to allow water, snow, and grit to disperse through the gaps between the treads as the tyre passes over the road surface. As a tyre wears down, its ability to do this is reduced, so it’s good practice to replace tyres when they reach 3mm of wear rather than waiting for them to go down to the legal minimum.

Advertisement - Article continues below

Different tyres have different tread patterns, but they must all meet the same legal requirements of at least 1.6mm of tread depth across three quarters of the tyre’s width.

How do you check tyre tread depth?

You should pay close attention to your tyre tread depth. The law requires a minimum tread depth of 1.6mm in a continuous band around the central three quarters of the tyre. You can check the tyre’s tread depth with a tyre tread depth gauge, but for a quick visual check, manufacturers often mould little bars into the tread at a height of 1.6mm. You can see or feel if these are flush with the tread – if they are, it’s time for new tyres.

The 20p test

If you don’t have a tyre depth gauge and are unsure about the amount of tread remaining, you can quickly check them with a 20p coin. Simply place the 20p in the main tread grooves of your tyre – if the outer band of the 20p piece is obscured, then your tyre is above the legal limit.

Skip advert
Advertisement
Skip advert
Advertisement - Article continues below

If the outer band of the coin is visible, your tyre may be illegal and should be checked by a garage. Remember to check at three different spots around the tyre to check for even wear. 

When should you change tyres?

The law states a tyre should not have less than 1.6mm of tread depth across three quarters of its with. However, it’s a very good idea to replace tyres before they reach that point. It means you don’t risk breaking the law, but tyre performance is maintained as tyres lose a lot of their ability to disperse water and provide the best braking when they drop below 3mm tread depth. A tyre with 1.6mm tread depth can take 50% longer to stop on a wet road than one with 3mm of tread depth.

It's also a good idea to replace tyres in pairs, so if you need to change the front left tyre it’s a wise idea to replace the front right one at the same time. This applies unless you know the other tyre has plenty of tread and is in good condition – just make sure the replacement is the same make and type of tyre as it’s safest to use the same tyres on each axle. And don’t mix summer and winter tyres on the same axle as it will affect the car’s braking, steering, and handling.

What about tyre condition?

Checking your tyre’s tread depth and general condition is vital routine maintenance. Giving them a visual inspection will allow you to look for any nails or sharp objects which may have punctured and become stuck in the tread or sidewalls.

Keep an eye out for any odd-shaped bulges, cuts or cracks as these can weaken the tyre and result in a tyre blow out without warning and potentially losing control of the car. If you do spot anything, get it inspected by a professional mechanic or tyre fitting centre.

Frequently Asked Questions

In the UK, the law says a tyre must have at least 1.6mm of tread depth across three quarters of its width. However, if a tyre is worn below this depth on any part of its tread, it’s best to change the tyre as its performance will be compromised.

A tyre might have the minimum 1.6mm tread depth on three quarters of its width but be worn dangerously on the edge. This could cause poor braking, a sudden blow-out, or land you with a fine and penalty points.

Check out our in-depth test on the best all season tyres or best winter tyres...

Skip advert
Advertisement
Skip advert
Advertisement

Recommended

Car Product Awards 2025: the very best kit for your car
Auto Express products editor Tom Barnard standing with a selection of award-winning car care products

Car Product Awards 2025: the very best kit for your car

From waxes and washes to tyres and tools, this is the top kit for your car
Awards
14 May 2025
Best pressure washers for cleaning your car
Alloy wheel being cleaned with pressure washer

Best pressure washers for cleaning your car

A pressure washer saves time and is better for your car than a bucket and sponge, but which is best?
Product group tests
2 May 2025
Best car wash options: what are hand, auto and jet washes doing to your car?
Best car wash options - header

Best car wash options: what are hand, auto and jet washes doing to your car?

Choosing the wrong car wash can cause thousands of pounds’ worth of damage to your car’s paintwork. Our experts tell you how to choose the best option
Tips & advice
30 Apr 2025
Ecomotive Tyrefix review
Ecomotive Tyrefix review

Ecomotive Tyrefix review

The Ecomotive Tyrefix sealant is an effective way to fix a puncture by the roadside, but it isn't as straightforward to use as cheaper aerosol rivals
Product reviews
15 Apr 2025

Most Popular

Flawed hybrid car efficiency data to stifle UK EV sales and propagate pollution
Connecting charger to Hyundai Tucson PHEV

Flawed hybrid car efficiency data to stifle UK EV sales and propagate pollution

Half a million extra PHEVs could reach UK roads by 2030 in place of cleaner EVs due to changes surrounding the ZEV Mandate
News
19 May 2025
New Ford Fiesta: latest details on supermini’s potential return
Ford Fiesta exclusive image

New Ford Fiesta: latest details on supermini’s potential return

The Ford Fiesta could be coming back as an electric car, and here’s everything we know so far
News
20 May 2025
Kia is returning to its 'Keeping It Affordable' roots
Opinion - Kia

Kia is returning to its 'Keeping It Affordable' roots

Mike Rutherford thinks new cars are simply too expensive, but some manufacturers are starting to do something about it
Opinion
19 May 2025