CASE STUDY

Case Study

Case Study

A tire is a device made of rubber and fabric and attached to the outer rim of a vehicle wheel. Solid rubber tires were in limited use before 1850; they are still used in some special applications, e.g., for industrial trucks in factories. The pneumatic rubber tire uses rubber and enclosed air to reduce vibration and improve traction. It was first patented by Robert W. Thomson, a Scottish civil engineer; however, it was not a commercial success until the Scottish inventor John Dunlop patented a pneumatic bicycle tire in 1888 and started a tire company.

The main parts of a modern pneumatic tire are its body, tread and sidewalls, and beads. The body is made of layers of rubberized fabric, called plies that give the tire strength and flexibility. Covering the plies are sidewalls and tread of chemically treated rubber. The sidewalls form the outer walls of the tire. The tread is a thick hoop of rubber that comes into direct contact with road surfaces. High-performance tires have treads optimized for warm weather, and winter (or snow) tires are optimized for cold and snow; all-season tires are general-purpose tires. Imbedded in the two inner edges of the tire are steel hoops, called beads that hold the tire to the wheel rim.

In the older type of pneumatic tire, air is sealed in an inner tube of butyl rubber beneath the body. In a tubeless tire the seal between the beads and the wheel rim is airtight and the underside of the tire body is coated with butyl rubber to keep the air from escaping. A puncture in a tire leads to loss of air and a so-called flat tire. Self-sealing tires are lined with a rubber or rubberlike compound that when the tire is punctured by a slim object, such as a nail, coats the object and seals the hole to prevent air from escaping. A recent innovation is the run-flat tire, in which the sidewall is reinforced so that, in case of a large puncture and a total loss of air pressure, the tire is self-supporting; the vehicle can continue operating as if there were no tire problem for up to 125 mi (200 km). An innovative bead design keeps the tire securely on the rim. Such tires are often linked to a pressure monitoring system that alerts the vehicle operator to the puncture.

The most important feature of tire design is the arrangement of the cord, or ply. The three main types are bias ply, radial-ply belted, and bias-ply belted. In a bias-ply tire the cords in a single ply run diagonally from the beads on one inner rim to the beads on the other. In a radial-ply (also called radial-ply belted) tire the cords in every ply run perpendicularly from the beads on one inner rim to the beads on the other, and there is a rigid belt, usually of fine steel wire, between the tread and the ...