Most drivers have heard of tyre tread depth. Whether you’ve experienced driving on worn tyres or seen it mentioned on your MOT bill, it’s important to check tyre health.

However, you don’t have to wait until your MOT or a maintenance bill to check your tyres. You can check them at home and catch issues early.

Below, we’ll discuss what tyre tread depth is, how to check it and what happens if you ignore your car’s tyre health.

What is tyre tread depth?

Tyre tread refers to the grooves on a car’s tyres, so the “depth” is how deep these grooves go. Tyre treads are important to maintain a grip on the roads, and poor depth can greatly reduce friction. Poorer friction means less effective braking and handling.

If the grooves become worn down and the depth becomes reduced, then a car becomes more difficult to drive – this is, of course, unacceptable. It becomes especially dangerous on wet and slippery roads. Deep grooves allow for water to run away from a tyre easily, while poor tread depth makes wet roads more slippery.

Even with the best tyres, the tread depth will eventually wear down. So, whether you have a high-quality car or a reliable old banger, you’ll need to know how to check tyre tread depth.

How to measure tyre tread

There are a few ways to measure tyre tread depth, with some being more accurate than others. The three major methods are the “20p test”, tyre tread depth indicators and a tyre tread depth gauge.

The 20p test is something anyone can do at home, while the other two methods are usually reserved for garages.

The 20p test

This is the go-to method for checking the tread from home and it couldn’t be more straightforward. The process is simple:

  1. Get a 20p coin and place it into one of the tyre grooves.
  2. Check the outer groove of the coin.
  3. If you can’t see the coin’s outer band, then your tyre depth is fine. If you can, then the tyre may need replacing.

This gives you a good indication of your tyre’s health as you can easily see how deep the tyre tread is. However, it isn’t as sophisticated as the other methods.

Tyre tread depth indicators and gauges

These are tools that the majority of mechanics and car garages will use. They test a tyre’s tread depth exactly and will be the basis for recommending replacements.

As a car owner, owning one of these isn’t essential, though consumer versions are available.

Tyre tread depth: what does the law say?

The legal requirement for tyre tread depth is 1.6mm for at least three-quarters of the tyre. This varies outside of the UK and Europe.

1.6mm is seen as the absolute minimum for safety. However, 3mm is seen as the recommended depth to get replacements. Despite only being 1.4mm more than the 1.6mm minimum, some estimations state that 3mm tyres are 40% safer.

If you ignore tyre tread depth, you can face numerous penalties. For example, if you are involved in an accident and it is found that your tyre tread depth is below par, then your insurance company can refuse the payout.

It is also illegal to drive with dangerous tyres. If you are caught with worn-out, defective tyres, then you can face a fine of £2,500 and 3 points on your licence. That fine is per tyre, by the way, so if your whole car has defective tyres, that’s £10,000 and 12 points.

To make sure you don’t get caught out by this fine, check your tyre depth regularly and learn how to change your tyre.

Discover high-quality used cars

At, we only stock high-quality used cars from trusted dealers. With us, you won’t have to worry about checking the tyre tread before purchasing a used car – you can drive away with peace of mind and a good deal.

Discover a variety of used cars today.

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