Car Tyre Construction

Most vehicles on our roads today are equipped with radial ply tyres, which have up to 30 individual components each with specific functions. The materials used include Natural and Synthetic rubber polymers, Aromatic Oil, Carbon Black, Silica, Steel cord and Fabric cords. The illustration below shows the main components in a modern day car tyre.

1. Tread - synthetic/ natural Rubber blend
2. Cap Ply - Nylon
3. Reinforcing Belts - Steel Cord
4. Radial Body Ply - Textile Cord
5. Inner Liner - Butyl Rubber
6. Sidewall - Rubber Veneer
7. Apex - Hard Rubber
8. Bead Wires - Steel Hoops
9. Bead Reinforcement - Textile
10. Rim Strip - Abrasion resistant Rubber

Main Components

The Tyre's Main Functions

Figure 1

It is the air within the tyre, which carries the load, not the tyre itself. Air inflation is to a tyre what petrol or diesel is to an engine, it is its fuel. Half fill the petrol tank in a car and it will only travel half the distance it would with a full tank the same principle applies to air inflation and tyres. The less air you put inside the tyre, the less mileage it will achieve. Additional under-inflated tyres will cause the car to use more fuel and compromise vehicle safety.

Figure 2

The tyre is the only contact the vehicle has with the road, hence it has to transmit both traction and braking forces to the road surface. A remarkable feat when you consider the area of contact with the road, for each tyre is about the size of the sole of a size 8 shoe.

Figure 3

When a car encounters a corner, centrifugal force tries to throw the vehicle off line. The tyres collectively have to generate an equa force to counteract the centrifugal force and hence keep the vehicle on its steered path. Even when travelling in a straight line, it is the tyres, which enable the vehicle to keep on its steered direction.

Figure 4

An inflation tyre and wheel unit bounces when dropped, indicating it is a spring. The tyre has to supplement the vehicle's suspension to provide passenger comfort.

The Tyre's Supplementary Functions:

The tyre has to perform many functions and listed below are some of them:

The tyre has to:

• be compatible with different suspension systems
• give quick response to steering response
• provide grip on a variety of different road surfaces
• withstand wear and tear
• withstand user abuse and neglect
• operate in any weather condition
• operate quietly
• be produced from environmentally friendly materials
• be re-cyclable

In addition to the above, the average sized tyre will rotate approximately 880 times within one mile and the average mileage for a car tyre is 30,000 miles. This means during its service life the tyre will rotate more than 26,000,000 times. Each time it is in contact with the road it is deflected or distorted under the load of the vehicle and hence it is deformed more times than most other components on a vehicle.