How To Check Tyre Tread Depth

By David Sholicar

It is important to remember to check your tyre tread depths. Depending on a number of factors, you may or may not be entirely familiar with the term ‘tyre tread’. If you are unsure how to check your tyre tread or how to check your tyre tread depth, this article should help.

What is tyre tread?

A tyre’s tread is what helps to keep the tyre in contact with the road. As a tyre wears, the tread is reduced and the tyre's ability to grip the road decreases. A brand-new car tyre starts off with approximately 8mm of tread.

So, what is the legal tyre tread depth?

In the UK and Europe, the legal minimum tread depth for cars is 1.6mm. This is across the central three-quarters of the tyre and the tread must meet this minimum across its entire circumference.

What if my tread depth is below this?

At worst, you risk a fine of up to £2500 and three penalty points on your license for EACH tyre where the tread is below the legal limit. It can be a costly oversight!
From a safety point of view, driving on tyres with less tread than this can be dangerous and can mean:

  • Slower braking on wet roads

  • A higher risk of aquaplaning

  • Trouble gaining traction in icy or snowy conditions

  • Increased vulnerability to punctures, which can lead to a sudden blowout

What difference can a few millimetres make?

Research carried out by MIRA shows that tyres with 3mm of tread perform on average 25% better than those with a tread depth of 1.6mm. This represents significant extra stopping distance, especially in wet conditions.

How to measure tyre tread depth

There are three main ways of measuring/checking your tyre tread depth.

Method 1: The 20p test

This is a simple, quick and effective way of checking the amount of remaining tread on a tyre. All you need is a 20p coin.
Take the coin and insert it into the tread grooves on your tyre.
If, when you have inserted the coin, you cannot see the outer band of the coin, this indicates that your tyre is above the legal limit of 1.6mm. However, if you can see the outer band of the coin and that section of the coin remains visible, this is an indication that the tyre is likely to be below the legal limit so you should arrange a professional inspection by a mechanic as a matter of urgency.
It is recommended that regular drivers conduct the 20p test approximately every two weeks and also before undertaking any extra-long journeys.

20pence tread depth test

Method 2: Tyre tread wear indicators

Most modern tyres have Tread Wear Indicator (TWI) bars/blocks that are moulded into the tread grooves at set intervals around the tyre.
If the tyre is flush with these bars, it means the tread is below the legal limit and the tyre needs replacing ASAP. However, most car manufacturers recommend that you replace tyres long before they wear to that extent - indeed, as above, many suggest replacing tyres as soon as the remaining tread falls below 3mm.

Method 3: Tyre tread depth gauge

These are purpose made tools that are able to measure the depth of an individual tyre groove.

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What happens if you have an accident on illegal tyres?

If you have an accident where the cause can be traced to illegal/bald tyres, your insurance may be invalidated

What can cause tyre tread wear?

Tyres will inevitably wear out over time, but some other factors can impact on the level of wear on the tread. These include:

  • Driving with an excess load

  • Driving (and cornering) at high speeds

  • Incorrect inflation of tyres - over or under

  • Misaligned wheels

  • Worn suspension components

  • Seized component in the braking system

  • Driving style

The local garage you can trust

All garages in the Protyre network stock a wide range of premium tyres from the likes of Pirelli, Goodyear, Bridgestone, and Falken. We also have lower-budget and mid-range options available. Our tyre professionals have years of experience and are always happy to help if you have any queries or questions about your existing tyres, or about which replacements you should opt for.
If you feel that your tyres are underperforming or may be coming towards the end of their life, why not book a free tyre check at a Protyre garage near you? To find your closest Protyre, click the button below and simply enter your postcode.

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About the author

Article Author Photo
By David Sholicar
David is the National Retail Operations Manager for Protyre. One of David’s areas of responsibility and expertise is dealing with the DVSA and MOT’s for Protyre. As the Authorised Examiner Designate Manager ( AEDM ) David deals with applications for changes to the many Vehicle Testing Stations ( VTS’s) including managing the growth of the Number of MOT testing stations that Protyre operate, allocating MOT tester roles, and monitoring the MOT Test logs to ensure that Protyre MOT standards are maintained as the best in the industry.
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