BK Tyres’ guide to the anatomy of a tyre

Although we’ve blogged about different types of tyres – for example, run-flats, unidirectional tyres, and even part-worn tyres – it suddenly occurred to us that we hadn’t really looked at the basic question of what’s inside a typical tyre. So with that in mind, here’s the BK Tyres’ five minute course on tyre anatomy.

Tyres may seem straightforward rubber rings, but appearances can be deceptive. A tyre may not be glamorous, but in its own way, it’s a technological marvel. Modern tyres have multiple components manufactured from dozens of advanced materials. In fact, let’s start with those.

What are tyres made from?

It takes around 200 different raw materials to make a modern tyre. The principal constituents, not surprisingly, is rubber. But that term covers a lot of bases, with a typical passenger tyre containing 30 types of synthetic rubber and 8 types of natural rubber.

Rubber accounts for about half of the tyre’s weight, with a further 20% coming from carbon black. Produced by the incomplete combustion of petroleum compounds, this dark powdery or granular material is – as the name suggests – mainly carbon. It’s used in tyres as a reinforcer and to reduce wear from abrasion. In high performance tyres, silica is used alongside carbon black to prevent heat build up.

Other important materials in your tyre include:

  • metals  – such as the steel used in tyre bands (see below)
  • textiles  – to reinforce the tyre carcass
  • antioxidants  – to slow the damage of the sidewall by UV light
  • sulphur  – to vulcanise the rubbers for greater durability.

If you think this sounds like a toxic waste dump, you’d be wrong – actually tyres contain relatively few hazardous materials.

The next question is what structures all those materials are made into.

The structure of a tyre

Even the most basic of modern tyres has a complex internal anatomy. The result of decades of research, all the structures within the tyre work together in harmony. The principal components include:

  • Tread. The most visible and obvious component of your tyre, the tread is actually only a third of its total weight. The tread forms the outer layer in contact with the road and is designed to provide cushioning and grip.
  • Bead. Beads hold the tyre on the wheel-rim. They’re manufactured from steel, coated in bronze or brass to resist corrosion, then coated again in rubber. Needless to say they’re incredibly strong.
  • Sidewall. Sidewalls lie between the bead and the tread. The rubber here is thicker and gives the tyre stability. The material is also designed to resist abrasion from kerbs.
  • Belt. Lying beneath the tread, the belt resists centrifugal force that would otherwise distort a spinning tyre. Typically, belts are made from woven steel, sometimes with Kevlar added.
  • Plies. Beneath the belt, the plies are layers that, among other functions, add strength and resist pressure. Plies are made from layers of textiles sandwiched between rubber and are designed to flex without stretching. The textile components may include rayon, nylon or Kevlar.
  • Inner Liner. Under the plies, the inner liner is the component that is inflated under pressure – effectively the tyre’s ‘inner tube’. As expected, the synthetic rubber used is designed to be air-tight!

Let’s hear it for tyre technology!

The result of all this engineering and chemistry know-how is a product with near-miraculous properties. Modern tyres last for thousands of miles, accommodate a huge range of temperatures, grip both wet and dry surfaces, and deal with terrible road surfaces (and neglectful drivers). They do all of this filled with high pressure gas, spinning tens of times a second and supporting hundreds of kilos of metal. So let’s hear it for tyre technology, the unsung hero of our age!

To get all this advanced technology fitted to your car (and at a competitive price), please get in touch.

Sources for our article included: