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Tyre Basics

Don’t judge a book by its cover.

Michelin 18 May 2010

STRUCTURE OF A TYRE

At first sight a tyre is just black and round with a hole in the middle.  Look a bit more deeply, however, and you'll see quite a different story.

The MICHELIN tyre is a complex piece of high technology, consisting of dozens of components using a wide variety of raw materials, that is essential for your safety and the efficient running of your vehicle.

The composition of the rubber varies within the same tyre. Each material has very different properties, whose manufacture demands great precision. Each is meticulously designed for the requirements of flexibility and strength, grip and so on. Huge lengths of metal and synthetic wires and cords are also used.

 

Structure of a tyre

What’s the structure of a tyre?

Many layers go into the finished tyre, they are:

1. Inner liner

A layer of airtight synthetic rubber, this is the modern equivalent of the inner tube. Check your air pressure monthly and before long journeys, as some air loss occurs over time.

2. Casing ply

Made up of thin textile fibre cords bonded into the rubber, laid down in straight lines and sandwiched in rubber. These cords are largely responsible for determining the strength of the tyre and help it to resist pressure: there are about 1,400 cords, each one of which can resist a force of 15 kg.

3. Lower bead area

This is where the rubber tyre grips the metal rim. The power from the engine and braking effort is transmitted from the rim of the tyre to the contact patch with the road's surface. This contact patch is no bigger than a human hand.

4. Bead wires

These clamp the tyre firmly against the wheel rim for maximum strength. Each wire can take a load of up to 1,800 kg without the risk of breakage. There are eight of them on your car, two per tyre. That’s a massive 14,400 kg of strength: an average car weighs about 1,500 kg.

5. Sidewall

Protects the tyre against impacts with pavements, potholes etc. This hard, protective rubber sidewall also has markings that tell you important information regarding the tyre.

6. Casing ply

Largely responsible for determining the strength of the tyre, the casing ply is made up of very fine, resistant steel cords bonded into the rubber. MICHELIN has mastered the art of perfect bonding, which is absolutely essential to your safety. This means the tyre can resist the stresses and strains of cornering and doesn't expand due to the rotation of the tyre. It's also flexible enough to absorb deformations caused by bumps, potholes and other obstacles in the road.

7. Cap ply

Sometimes called the 'zero degree' belt, this important safety layer reduces friction heating and helps maintain the shape of the tyre when travelling at speed. To prevent centrifugal stretching of the tyre, reinforced nylon based cords are bedded in a layer of rubber and laid around the circumference of the tyre.

8. Tread

Because the contact patch, the tread part of the tyre that touches the road, is only the size of a human hand, the tread is designed to resist very significant stresses. It also grips all types of surfaces, resists wear and abrasion, and heats up as little as possible. So it has a big job to do.
So this amazing composite structure is far more than just black and round with a hole in the middle.
  • car
  • 4x4 / suv
  • van / motorhome
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