Why Are My Car Tyres Cracking And What Can I Do?

Bradley Jando | Monday 1st March 2021 3:35pm

Tyre with damaged sidewall

Tyres are highly engineered pieces of equipment and theyíre arguably one of the most important parts of your car. Without them, your car wouldn't be able to move. However, tyres donít last forever, and there are some signs of wear and tear that you need to look out for, including cracking.

But why have your tyres cracked, and is there a way to fix them?

What causes tyres to crack?

There are a number of components that help to make tyres strong enough to hold the weight of your car and enable them to keep their shape under pressure. These components include plies (the fibres inside the tyre that give it some flexibility while maintaining its structure) and beads (steel thatís coated in rubber to create a seal between the tyre and the wheel rim).

The rubber on the outside of the tyre is made up of lots of polymers that are knitted together to form molecules. Tyre cracking is caused by these bonds breaking down. But what is it that causes these bonds to weaken in the first place?

man holding a tyre with a crack on the sidewall

UV rays/ extreme heat

The polymers in the tyre can expand in the heat and contract in the cold. This constant movement can weaken the bonds over time, which is when cracks begin to appear. UV rays can also have the same effect.

UV rays are one of the biggest causes of cracked tyres, because itís nearly impossible for most people to store their tyres correctly in a garage or park in the shade all the time. However, recent technological advancements mean that you can actually paint UV-resistant paint (or sprays) in your tyres in order to protect them from UV rays.


As your tyres get older, the polymers naturally weaken and begin to break down. This causes your tyres to harden and become brittle - and this loss of elasticity can mean the tyres crack. Even if your car hasnít been driven for a few years and is stored in a garage, the tyres can still weaken and crack.

Itís actually more beneficial to drive your car every now and then instead of leaving it parked. The chemical that prevents the tyre from drying out and cracking is released when the tyre is moving. Therefore, if the car is parked for a long time, this chemical wonít be able to work efficiently.

Find out how to tell what age your tyres are here.


Rubber is mainly waterproof, however water can still permeate the tyre after driving on wet roads for a prolonged period of time. This water can then have the effect of either sloshing around inside the tyre Ė which wears it down from the inside Ė or having a similar effect to potholes. As the water expands and contracts in partial cracks of your tyres, it makes them larger.


Tyres are made of rubber, which is an organic material thatís taken from trees. This makes them biodegradable and no amount of chemicals will stop your tyres from naturally degrading over time.

Certain chemicals and compounds are applied when your tyres are made to reinforce them and slow down degradation; however, these wonít work forever.

Tyre pressure

If your tyres are inflated incorrectly, cracking can occur. With under pressurised tyres, more heat is created when youíre driving. This is because more of the surface of an underinflated tyre is in contact with the road, which creates more friction. Over pressurised tyres can add extra stress to the tyre wall and cause bulging.

You can check whether your tyres are the right pressure using a pressure meter, or through our tyre pressure checking tool. Simply input your carís registration number and youíll see what your recommended tyre pressure is.

Are cracked tyres dangerous?

You should avoid driving with cracked tyres. This is because the tyreís rigidity and strength have been compromised and you could experience a blowout while driving.

If you notice cracks around your tyres, you should take your car to a garage and have new ones fitted.

Do cracked tyres need replacing?

Yes, cracked tyres should be replaced right away. It indicates that there is a problem with the tyre, which could be caused by deterioration over time, low air pressure, or a variety of environmental causes. Cracks can form on the side and top of a tyre and are a source of concern for drivers because they can render a vehicle unroadworthy, unsafe, and may lead to more problems with yourvehicle.

Are cracked tyres an MOT failure?

An MOT test will involve all four tyres being checked for damage and general wear and tear. When you take your car for its test, the tyres should have a tread depth of at least 1.6mm (the legal minimum) and there shouldnít be any tears, bulges, or cracks around the tyre.

Your car may receive an MOT failure if itís determined that the tyres arenít safe to drive with. If your car does pass its MOT, it could be worth determining with the garage the state of your tyres, as they may be borderline or could need to be replaced soon. The garage will be able to tell you the tyresí tread and what condition theyíre in.

How to fix cracked tyres

Itís not recommended that you try to fix your cracked tyres as their structure has been permanently weakened and no amount of chemicals will be able to bring your tyre back. However, there are preventative measures that you can put in place when your tyres are in good condition to prevent them from cracking.

How to make tyres last longer

You should ensure that your tyres are inflated to the tyre manufacturerís recommendations and ensure that youíre driving your vehicle regularly. Also, where possible, try to park in the shade or in a garage.

You could apply a tyre protector to your tyres regularly. There are lots of brands that create these solutions, which are made to protect the rubber from UV and environmental damage as well as repel dust, dirt, and water. Just make sure that you use a water based solution, as harsh chemicals can speed up the cracking process.

Once the tyres have begun to crack, they are still okay to drive with if the cracks arenít too big or deep. However, the fungus that causes dry rot in wood, Serpula lacrymans, could start to attack the rubber on your tyres. By keeping your tyres clean, youíll help to prevent the fungus from spreading further, so clean your tyres regularly with warm, soapy water.

Having a qualified professional check your car tyres can help them to last longer. Come down to your local Kwik Fit centre for a free tyre check. Or, in the meantime, if you have any questions about the condition of your tyres or tyre care in general, speak to our friendly team of experts and we can point you in the right direction.

Tags : Tips Tyres

Any facts, figures and prices shown in our blog articles are correct at time of publication.

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