From a safety standpoint, your tyres are the most important car component. But because they’re subject to immense wear and tear (even when you don’t drive your car), they don’t last forever.
Tyre cracks aren’t uncommon, but they can be dangerous, and in some instances, lead to a blowout. To help you stay safe on the road, here’s everything you need to know about tyre cracks.
Why do tyres crack?
Tyres feature several components. And, it’s these components that make the tyre strong enough to hold the weight of your car while keeping its shape. The components include:
- Tread: The tread of a tyre has three elements (Cap, Base and Shoulder) responsible for good grip, water expulsion and low rolling resistance.
- Jointless cap plies: This layer is a single nylon cord cased in rubber. It sits directly below the tread and makes high-speed travel possible.
- Steel cord belt plies: Strong steel cords keep the tyre’s shape, enhance directional stability, reduce rolling noise and increase the tyre’s mileage performance.
- Textile cord ply: A layer controls the internal pressure of the tyre and keeps its shape.
- Inner liner: An airtight layer of butyl rubber controls tyre pressure and acts as an inner tube in tubeless tyres.
- Sidewall: The exterior wall of the tyre protects the casing from damage.
- Bead reinforcement: Made of nylon or aramid, it enhances directional stability and steering precision.
- Bead apex: A wedge of synthetic rubber that gives the tyre additional steering comfort.
- Bead core: A steel wire embedded in rubber makes sure the tyre sits firmly on the wheel rim.
Tyre cracking is caused by one of these components breaking down. But what causes them to break down?
It’s no surprise that age is on this list. As a tyre gets older, the polymers naturally weaken and start to break down. As this happens, the tyre gets harder, loses elasticity, becomes more brittle and eventually cracks. This can happen to any tyre, whether it’s in use or left in a garage.
It is beneficial to drive your car, though. Because did you know there’s a chemical inside that prevents it from drying out and cracking? But here’s the thing, it’s only released when the tyre is in motion, which is why we advise a quick spin now and then.
Extreme heat & UV rays
Like most things, the polymers in a tyre expand when they’re hot and contract when they’re cold. This, plus constant movement, causes cracking in the tyre’s sidewall. Like extreme heat, UV rays have the same effect.
In fact, UV rays are what causes most tyre cracks, as it’s almost impossible to keep a car out of direct sunlight. Because of this, UV resistant paints and sprays exist for your tyres.
If it’s not heat or age, it could be under or overinflation. An underinflated tyre generates a lot more heat as the contact patch is wider. Because of this, friction is greater.
Driving with an overinflated tyre is also risky. Too much air can cause bulging, adding pressure to the sidewall, and in turn, causing cracking.
You can check your tyre’s pressure with a pressure gauge. Or head to your local First Stop garage, where we can do it for you.
Rubber is waterproof. But like all waterproof things, it’s not 100% protected from water damage. If a tyre is exposed to water for a lengthy spell, like on a long drive in constant rain, it can start to break down the tyre’s elasticity. As more and more water gets in, cracks appear and expand over time.
Because rubber is an organic material that comes from trees, most tyres contain biodegradable elements. And because of this, they’ll naturally degrade over time. While anti-ageing treatments exist to slow down ageing, nothing will stop it entirely.
Do cracked tyres need replacing?
Short answer, yes. Cracks and slits compromise tyre strength and durability, which can affect its performance. And in some cases, lead to a blowout. Thus, if your tyres have cracks in them, you should get them looked at.
If the cracks are small and shallow, you’ll still be able to drive. But if you notice a large or deep crack, you should head to your local garage immediately. Sometimes it can be hard to spot a small crack, but if your tyres are deflating faster than normal, get them checked out.
Are cracked tyres an NCT failure?
An NCT test is a thorough check of every essential car component, including all four tyres. The NCT tester will check your tyres have at least 1.6mm tread depth (the legal limit) and that there aren’t any tears, bulges or cracks.
It’s not uncommon for a car to fail an NCT test because of cracked tyres, as they can be dangerous to drive on. Even if your car does pass, it’s always worth asking the garage about your tyres. It may be a case that they’re only slightly on the side of passable.
Can I fix cracked tyres?
While it is possible to repair small and shallow cracks, we don't recommend it. The cracks will weaken the structure of the tyre, taking it beyond repair. No amount of solutions or chemicals can fix this.
But it’s not all doom and gloom. There are things you can do to help prevent your tyres from cracking in the first place. So let’s have a look.
How to protect your tyres from cracking - Keep your car sheltered (or in the shade)
There’s no way to protect your tyres from the elements when on the road. But you can protect it from extreme heat, UV rays and water when you’re not using it by parking in a garage or the shade. Basically, anywhere out of direct sunlight.
Make sure your tyres are inflated (as per the numbers in your vehicle’s handbook)
You should check your tyre pressure often anyway, but it’s vital if you want to avoid cracking. Inflate your tyres using the numbers in your vehicle’s handbook or on the inside of the petrol cap.
And remember, avoid leaving your car sitting in the same place for a long time, as this can damage a tyre’s elasticity.
Use a tyre protector
Tyre protectors prevent cracking too. And there are lots available, protecting the rubber from UV rays, grit, dirt and water. Make sure you choose a water-based solution, as harsh chemicals can in fact cause cracks.
So there we have it! Nothing beats having a professional check your tyres, so head to your local First Stop garage. We’ll give them a thorough check, and help you find a replacement if they have any flaws.