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Shop Talk: Under the skin

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Tyres are designed, manufactured and tested to meet strict governmental requirements, manufacturer requirements, vehicle performance characteristics and consumer expectations. That is a lot of expectation.

Modern tyre technology blends a unique mix of chemistry, physics and engineering to give consumers a high level of tyre performance in the areas of safety, reliability, efficiency, long wear and comfort. Tyre use however is to some degree out of the hands of the manufacturer, so if consumers want their tyre service life to match the cost, it’s best to maintain a proper schedule of tyre care, which means regular balancing and rotation.

Construction

These days, nearly all passenger and light truck tyres are radial ply construction; the orientation of the body cords provides sidewall flexibility. Cords form the ply and the bead, providing the strength necessary to contain inflation pressure. Cords can be composed of steel, natural fibres such as cotton or silk, or synthetic fibres such as nylon or Kevlar. Body cords run across the tyre nearly perpendicular to the beads. Radial tyres have belt plies with steel and/or other cords laid diagonally under the tread to stabilise and reinforce the tread area during contact with the road.

Passenger tyre vs Light truck

Passenger and light truck tyres are constructed differently due to their different uses and operating conditions. Compared to passenger tyres, light truck tyres usually operate at higher inflation pressures and carry greater loads on a regular basis. Light truck tyres are typically designed for more severe service such as in commercial vehicle applications or for off-road use.

In order to meet these performance needs, light truck tyres may have additional components/layers and heavier-duty materials. They will also therefore be heavier than a passenger tyre of the same size.

Compounds

Rubber compounding is a complex science of mixing different raw materials together to produce an elastomer with specific characteristics.   These elastomers differ due to their location and functional purpose in the tyre. For example, the outside tread compound provides traction and treadwear characteristics.

Although rubber is the main material used for making tyres there are a number of other materials used, such as silica and carbon black. Very simply put, silica is a high-cost element that helps improve grip/traction when combined with other compounds; carbon black is primarily a pigment that helps extend tyre life by conducting heat away from the tread.

These materials are combined with specific elastomers in the different components that make up the tyre’s construction. Each component contains a rubber compound made of 10 to 20 speciality chemicals, polymers and reinforcements.

Some of the components are composites of steel and rubber, or textiles and rubber, to provide strength and load-carrying capacity.

The combination of rubber compounds and reinforcement composites is specific to each tyre specification produced.
By Johann Viljoen

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