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4 April 2025 (updated) Tyre cracking explained: What causes tyres to perish & how to stay safe on UK roads
Your car's tyres are the only point of contact between your vehicle and the road, making them vital for safety and performance. Over time, tyres can perish and develop cracks due to factors such as age, exposure to sunlight, and fluctuating temperatures – all common on UK roads. These affect grip, handling, and braking, increasing the risk of punctures and accidents. You can prevent further damage and stay safer on the road by spotting these cracks early and repairing them by replacing or servicing your tyres. In this article, we'll look at the causes of tyre cracking and give practical tips on preventing it.
Why do tyres crack: causes
The rubber compounds in tyres expand in hot temperatures and contract in the cold. This constant cycle of expansion and contraction gradually weakens the rubber, leading to cracks. Similarly, prolonged exposure to intense UV rays speeds this process up. Here are some typical reasons why tyres develop cracks:
- Temperature fluctuations: Repeated heating and cooling cause the rubber to expand and contract, making it brittle over time.
- UV exposure: Sunlight breaks down rubber compounds, causing surface cracks. Parking in shaded areas can help minimise this effect.
- Ozone damage: Ozone in the atmosphere reacts with rubber, causing tiny fissures, especially on sidewalls. Using protective sprays can help.
- Underinflation: Insufficient air pressure makes sidewalls flex more, increasing the risk of cracking. Be sure to regularly check your tyre pressure.
- Chemical exposure: Oil, grease, and certain cleaning agents can deteriorate rubber, making it prone to cracking. We recommend using tyre-friendly products for cleaning.
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Types of tyre cracking
Tyre cracks can take different forms, each indicating different underlying problems that could compromise your safety. A common issue is edge cracking, which occurs along the outer edges of the tread. This is usually caused by underinflation or excessive stress when cornering. If you notice this, it's a sign that your tyres need immediate attention.
Another type to look out for is sidewall cracking – those fine lines or deeper cracks on the sidewalls. These are often the result of prolonged UV exposure, ozone damage, or the natural wear of the rubber. Because sidewall cracks weaken the tyre's structure, if you ignore them, this could increase the risk of tyre failure.
There's also tread cracking, which appears as small cracks between the tread blocks. This is usually caused by heat, prolonged use, or contact with harsh chemicals and debris.
You can prevent further damage and keep safe on the road by detecting these cracks early and repairing them by replacing or servicing your tyres. Make sure to get regular inspections as these are a simple but effective way to spot these signs before they become a serious hazard.
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Tyre cracking between tread: How dangerous is it?
If you're wondering whether cracked tyres inside the tread are dangerous, the answer is yes. You should get them inspected by a trusted tyre professional as soon as possible. Even if the tread depth seems fine, these cracks can compromise the tyre's integrity and lead to sudden failures, especially at high speeds.
Tread cracks allow moisture and debris to penetrate deeper into the tyre, accelerating wear and weakening the internal structure increasing the risk of blowouts, reduced traction, and poor handling in wet conditions. Typically, the safest course of action for tyres with visible tread cracks is to replace them.
Small cracks in tyre sidewall
Small cracks in the tyre sidewall are a clear sign that your tyres are getting older and the rubber is starting to degrade. As the rubber stiffens, the risk of a blowout at high speeds increases greatly, posing a serious danger not only to your safety but also to other road users.
Sidewall cracks weaken the tyre’s structure, which causes a reduction in its ability to handle stress during turns or sudden stops. Even minor cracks can expand quickly, especially under high temperatures and heavy loads. If you spot these, it's best to have a professional inspect your tyres right away.
Are cracked tyres illegal?
Cracked tyres are not inherently illegal, but they can become so if they do not meet legal safety standards. For example, tyres with visible damage such as deep cracks, exposed cords, or tread separation are considered unsafe and can result in fines or penalties if inspected by the authorities.
In addition, tyres with cracks that compromise their structural integrity will fail an MOT test, even if the tread depth is still within legal limits. Minor surface cracks may not be immediately illegal, but they are a warning sign of wear and should be addressed immediately. Driving on badly cracked tyres increases the risk of punctures and accidents, making replacement the safest option to ensure compliance and road safety.
Cracked tyres: MOT
Cracks in your car tyres can do more than just weaken their performance and safety – they could even cause your vehicle to fail its MOT. Often the result of UV exposure, deterioration, or poor maintenance, these cracks compromise the integrity of the tyre and increase the likelihood of punctures or tread separation.
Even if your tread depth meets legal requirements, worn tyres can drastically reduce grip, especially in wet or icy conditions. Those tiny surface cracks might look harmless, but they can quickly spread into bigger, more dangerous issues. That’s why regularly checking your tyres and replacing them when needed is essential for your safety and to keep you road-legal.
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How long should tyres last before cracking?
Because they are made of rubber, tyres will naturally wear or develop cracks over time – even if you don’t drive your car very much. Typically, they last about 5 to 10 years before cracking becomes a problem, depending on their quality, maintenance, and environmental factors. After 5 years, it's wise to have them regularly inspected by a professional, as ageing rubber loses elasticity and can crack due to UV exposure, heat or improper storage.
Your driving habits and road conditions also play a role; aggressive driving or rough surfaces can accelerate tyre degradation. It’s advisable to replace tyres showing noticeable cracks or once they reach the 10-year mark, regardless of tread condition, to keep you and your passengers safe.
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When to replace your tyres in case of cracking
If you notice cracks in your tyres, it's best to replace them immediately. Ignoring cracked tyres can lead to a blowout, which could cause you to lose control of your vehicle – a risk not worth taking. Even small ones can get worse quickly, so as soon as you spot them you should consider using your car's spare wheel until you can get a proper replacement.
But how many cracks are too many? Generally, any cracks that expose the inner layers or run deep into the sidewall are a clear sign that a replacement is needed. Stay vigilant and proactive with your tyre maintenance and you will substantially lower the risk of tyre-related accidents and ensure the safety of your journey.
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