2 mins

What is the tyre tread depth test

December 12, 2023

Tyres are the unsung heroes of our vehicles. They grip the road, provide stability, and keep us moving forward. But, like all good things, tyres wear out over time.

Tyre tread depth is also one of the many things that are checked during an MOT and is the biggest cause of MOT failures in the UK.

In this article, we'll take a closer look at the tyre tread depth test. We'll also cover the 20p tyre test and tyre tread depth checker tools to make the process as easy as possible.

What is tyre tread depth and why is it important?

Tyre tread depth refers to the measurement of the remaining tread on a tyre. Tyre tread is the pattern of grooves, blocks, and channels on the surface of a tyre that make contact with the road. It is designed to provide grip, channel water away from the contact patch, and maintain traction in various driving conditions.

Legal Requirements for Tyre Tread Depth

Tread depth is usually measured in millimetres (mm) and in the UK, the minimum legal tyre tread depth is 1.6mm.

What is the tyre tread depth test?

The tyre tread depth test is a crucial yet straightforward assessment of tyre tread that every vehicle owner should be aware of to ensure optimal safety and performance on the road. It’s one of the pre-checks many garages recommended all drivers do to minimise the risk of failing an MOT.

Tyre tread depth can be tested using a specialised gauge which measures the distance between the top of the tread and the bottom of the groove, or by using the popular 20p coin test.

How to check tyre tread depth using a gauge

The most accurate method is to use a tyre tread depth gauge which can easily be bought online. Then, follow these steps:

  1. Locate the main groove of the tyre and insert the probe of the gauge
  2. Ensure that the probe is perpendicular to the tyre surface
  3. If the gauge measurement is below 1.6mm, the tyre needs to be replaced immediately
  4. Repeat the process for each main groove of the tyre and in different parts of the tyre

Alternatively, you can use the 20p tyre test.

How to check tyre tread depth using the 20p tyre test

The 20p tyre test is a popular and straightforward method for checking your tyre tread depth. It's also a great way to put your loose change to good use. Here's how to do it:

  1. Insert a 20p coin into the main groove of the tyre
  2. Ensure that the border of the coin is inserted into the groove
  3. Check if the outer band of the coin is visible. If it's visible, it means that the tyre tread is below the legal tyre tread depth of 1.6mm and should be replaced immediately
How to use the 20p tyre test method to measure tread depth

What are the consequences of driving with illegal/dangerous tyres?

Driving with illegal or dangerous tyres in the UK can have serious consequences, both legally and in terms of safety. If you are involved in an accident while using tyres that do not meet the minimum tread depth requirements or are in poor condition, you may face the following repercussions:

  • Legal penalties: driving with illegal tyres can result in fines of up to £2,500 per tyre and three penalty points on your driving licence for each illegal tyre. This means that if all four tyres are below the legal tyre tread limit, you could potentially receive a fine of £10,000 and 12 penalty points, which would result in an immediate driving ban
  • Insurance implications: if you have an accident your insurance company may refuse to cover your claim. This means you could be held financially responsible for any damages to your vehicle, other vehicles, or property, as well as any personal injury claims arising from the accident
  • Reduced safety: tyres with insufficient tread depth or in poor condition can significantly compromise your vehicle's handling, grip, and braking performance, especially in wet or slippery conditions. This increases the risk of accidents and jeopardises the safety of both you and other road users
  • Vehicle damage: driving on illegal or dangerous tyres can cause excessive wear and damage to other components of your vehicle, such as suspension and braking systems. This may result in costly repairs in the long run

When to Replace Your Tyres

Although the legal minimum tread depth is 1.6mm, many experts recommend replacing your tyres when the tread depth reaches 3mm. At this point, the tyre's performance in wet conditions starts to decline significantly, potentially compromising your safety.

In conclusion, checking your tyre tread depth is crucial for your safety and the safety of others on the road.

Ready to book your MOT?

When you book an MOT in Caura, you can choose from over 6000 vetted independent and main dealerships near you and book at great prices.

If you know your vehicle needs a tyre replacement, select 'Repair' and just let us know in the text-box field and the garage will inspect and replace your tyres if needed.

Not sure if your tyres need replacing? Don’t worry - if an MOT tester believes you need to have repairs, like tyre replacements, done before you can pass your MOT test, we will send you a quote for the repairs. Upon your approval, the garage will then make those repairs and conduct a free partial MOT retest.

Download Caura and book your MOT today!

We hope this article has given you some insights into the importance of tyre tread depth and how to check it. Remember, if your tyre treads are worn out, it's time to get new tyres.

As the famous car enthusiast Jay Leno once said, "Cars are like shoes - they need to fit you comfortably, and they need to be appropriate for the occasion." So, make sure your tyres fit your car and the occasion, and you'll be driving safely and comfortably for many miles to come.


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