A tire (in American English and Canadian English) or tyre (in Commonwealth Nations such as UK, Australia, and others) is a ring-shaped covering that fits around a wheel rim to protect it and enable better vehicle performance by providing a flexible cushion that absorbs shock while keeping the wheel in close contact with the ground. The word itself may be derived from the word “tie,” which refers to the outer steel ring part of a wooden cart wheel that ties the wood segments together.
The fundamental materials of modern tires are synthetic rubber, natural rubber, fabric and wire, along with other compound chemicals. They consist of a tread and a body. The tread provides traction while the body ensures support. Before rubber was invented, the first versions of tires were simply bands of metal that fitted around wooden wheels in order to prevent wear and tear. Today, the vast majority of tires arepneumatic inflatable structures, comprising a doughnut-shaped body of cords and wires encased in rubber and generally filled with compressed air to form an inflatable cushion. Pneumatic tires are used on many types of vehicles, such as bicycles, motorcycles, cars, trucks, earthmovers, and aircraft.
The Oxford English Dictionary suggests that the word derives from “attire”, while other sources suggest a connection with the verb “to tie”. From the 15th to the 17th centuries the spellings tire and tyre were used without distinction; but by 1700 tyre had become obsolete and tire remained as the settled spelling.