What makes your tyres illegal?

By Julia Freeman

There are a variety of challenges that can come with car ownership and driving on illegal tyres is something that catches out many drivers each and every year.

illegal tyres

What are illegal tyres?

Although they are manufactured to cover thousands of miles, there are a number of issues that can affect your vehicle's tyres, all of which can cause a range of safety issues. So, let's run through some of the specific factors that affect the legality of a tyre to give you a better understanding as to what you need to check when maintaining your vehicle.


1. Tread depth

In order to remain legal, tyres must meet the minimum legal tread depth, which is 1.6mm. This 1.6mm requirement applies to the central 75% of the tread surface around the entire circumference of the tyre.

Tyre treads are designed to channel debris and water away from the surface, which allows the tyre to grip firmly onto the road. When these channels start to show signs of wear and tear through normal usage, grooves in the tread pattern become less able to remove debris and water, which impacts its ability to remain in contact with the surface of the road. Clearly, this is a huge safety issue, which can impact everything from steering to braking.

If you are stopped by the police and are found to be driving with one or more tyres that don't meet the minimum tread depth requirements, you can expect to receive a fine and three points on your driving license.

Although the legal limit is 1.6mm, tyre professionals recommend replacing tyres that have a tread depth of 3mm to ensure that you aren't risking your safety every time you get into your vehicle in wet conditions.


2. Sidewall damage and significant wear

Tyres that are displaying significant signs of wear and tear are going to demonstrate signs of instability. The development of weak spots is common on worn tyres, which makes them more susceptible to blowouts that can cause major accidents.


If you notice any signs of sidewall damage, cracking and/or bulging, it is imperative to have them checked by an experienced professional to determine the severity of the issue. Even tiny stones, minor bumps or scrapes can burst unstable tyres, and bulging could be an indicator that the structure of the tyre is compromised.


Although it can be easy to overlook what appears to be a small sidewall scratch, it is important to get all damage checked to avoid blowouts. It is also worth noting that tyre defects typically result in a failed MOT, so replacing damaged tyres as soon as possible is always recommended.


3. Over or under inflated tyres

Maintaining proper tyre inflation is the only way to ensure that your vehicle's weight is being distributed evenly. Under inflated tyres are extremely common and are actually one of the most common causes of tyre failure.


In addition to resulting in penalty points on your driving license and potentially costly fines, under inflated tyres can also result in poor vehicle handling, create areas of uneven wear on the tread of your tyres, increase your vehicle's fuel consumption, and result in longer braking distances.


Similarly, over inflated tyres can also cause a variety of problems, including poor handling and traction, increased braking times, and uneven tyre tread wear.


4. Combinations of different tyre ply


Tyres are constructed from a rubber compound material, which is moulded around an internal cord system that essentially acts as a skeleton. The cord lattice or ply can be positioned in different ways, each of which have their own set of characteristics.


In the UK, it is illegal to combine tyres with a differing ply on the same vehicle because they each handle the vehicle's load differently. So, whether you prefer Bridgestone, Pirelli or any other tyre brand, you must ensure that each tyre has the same ply to comply with the law.


How will I know when to change car tyres?

In some cases, you'll know when it's time for new tyres when you can see visible wear, bulging on the sidewalls, cracks, slashes, and scratches. However, it is always easy to determine whether your tyres are experiencing a normal level of wear and tear for their age.


When it comes to tyre tread longevity, the front tyres of your vehicle are likely to last for approximately 20,000 miles. So, if you're driving 5,000 miles each year, your tyres may last for up to four years before needing to be changed.


However, it is important to emphasise that driving techniques differ, and the type of road surface you drive on can also have an impact on the longevity of your tyres. So, it will likely be beneficial to invest in a tyre tread depth gauge. These are handy, easy to use tools that allow drivers to ensure that their tyres meet legal tread depth requirements.


But, in short, you'll know that your tyres need replacing if you see any of the following issues:


- Worn down tyre tread

- Unexplained or increased loss of tyre pressure

- Cracks, bulges or slashes in the rubber

- Vibration through the steering, especially when driving at speed


Most brand new tyres come with around 8mm tread depth, however, even top quality tyres can experience significant wear over time.

How long will 5mm tyre tread last?

Typre longevity is impacted by a number of different factors. Tyres with a 5mm tread depth typically last for around 20,000 miles.

How long will 4mm tyre tread last?

4mm tyre treads will typically last for between 10,000 and 20,000 miles.

How long will 3mm tyre tread last?

It is reasonable to expect a 3mm tyre tread to last for between 5,000 and 10,000 miles. We don't recommend driving on tyres with less than a 3mm tread depth because braking distances are significantly increased, so we would always advise a tyre change at this point.

How long will 2mm tyre tread last?

If your tyres are only measuring a tread depth of 2mm, it is likely that they will have a lifespan of less than 1,000 miles, and they should be changed immediately.

Book A Free Tyre Check

What will happen if I drive with illegal tyres?

Not only is driving a vehicle with illegal tyres extremely irresponsible and dangerous, but doing so could also lead to:

- Receiving 3 points on your driving license

- A fine of up to £2,500 for every illegal tyre

- An invalidated vehicle insurance policy

Speak to your local garage

As it is critical to ensure that your tyres comply with the law and are 100% roadworthy, it is important to have them checked frequently by an experienced and knowledgeable professional.


If you are concerned about your tyres or you just want to have them checked for your own peace of mind, our tyre professionals are on hand to help. Simply book your free tyre check online today or contact your local Protyre garage directly.

Buy Tyres

Share with your friends...

About the author

Article Author Photo
By Julia Freeman
Julia is Head of Retail Marketing for Protyre and loves engaging with customers and the business as a whole to make sure Protyre is more than just a local garage.
View authorArrow right
Is Driving With A Flat Tyre Illegal?
It can be frightening to incur a sudden puncture when you’re driving, and it can be exceptionally frustrating to go out to your vehicle and find that a tyre has suddenly gone flat. As tyres are made of rubber, they are highly susceptible to damage caused by debris left in the road. Rubble and sharp objects such as screws, nails, and glass can pierce the threads of your tyres or become embedded in the body of the tyre itself.
Find out moreChevron
How far can I drive on run flat tyres?
Whilst none of us are trying to break any records for driving the longest distance on a run flat tyre, in this day and age where we all need to keep moving the question as to how long you can keep going is a valid one. With 2 million tyres fitted each year, our tyre professionals at Protyre have offered some helpful advice on just how far you can drive on run flat tyres. Read more about puncture repair.
Find out moreChevron
Is 5mm tread on car tyres still good to drive on?
Driving with insufficient tread on your tyres is not only a safety issue but also a legal one. Failure to drive with tyres with sufficient tread can incur a fine of up to £2,500 plus three penalty points - for each tyre affected. Checking your tyres regularly will mean you don't end up making a costly error.
Find out moreChevron