Like every other part of your vehicle, the tires that keep you in solid contact with the road surface has evolved over the years. Consisting of many different compounds and constructions for a variety of applications, today’s passenger car tire is a marvel of technology and utility. First, a brief history of modern passenger car tire construction.
In the dawn of the modern transportation age, natural rubber served as the base of the tire’s construction and make-up. However, rubber was not always as useful as it is today. Early rubber did not hold shape; it would be sticky in hot weather and become inflexible in the cold. In 1839 Charles Goodyear was credited with the discovery of the vulcanization process. Vulcanization is the process of heating rubber with sulfur. This transforms sticky raw rubber to firm pliable material which makes rubber a perfect material for tires.
Solid Rubber Tires – Soon after the discovery of vulcanization, tires were made out of solid rubber. These tires were strong, absorbed shocks and resisted cuts and abrasions. Although they were a vast improvement, these tires were very heavy and did not provide a smooth ride.
Pneumatic Tires – The pneumatic tire uses rubber and enclosed air to reduce vibration and improve traction. Robert W. Thomson, a Scottish engineer, first patented the air-filled tire. In 1888 John Boyd Dunlop of Belfast, Ireland, became the second inventor of the pneumatic tire. Dunlop claimed to have no knowledge of Thomson’s earlier invention. The second time around, the pneumatic tire caught the public’s attention. The timing was perfect because bicycles were becoming extremely popular and the lighter tire provided a much better ride.
Bias Ply Tires – For the next fifty years, vehicle tires were made up of an inner tube that contained compressed air and an outer casing. This casing protected the inner tube and provided the tire with traction. Layers called plies reinforced the casing. The plies were made of rubberized fabric cords that were embedded in the rubber. These tires were known as bias ply tires. They were named bias ply because the cords in a single ply run diagonally from the beads on one inner rim to the beads on the other. However, the orientation of the cords is reversed from ply to ply so that the cords crisscross each other.
Radial Tires – (Also referred to as Steel Belted Radial Tires). The first introduced steel-belted radial tires appeared in Europe in 1948. Radial tires are so named because the ply cords radiate at a 90 degree angle from the wheel rim, and the casing is strengthened by a belt of steel fabric that runs around the circumference of the tire. Radial tire ply cords are made of nylon, rayon, or polyester. The advantages of radial tires include longer tread life, better steering and less rolling resistance, which increases gas mileage. On the other hand, radials have a harder riding quality, and are about twice as expensive to make.
Steel belted radial tires were introduced to the American marketplace by the B. F. Goodrich and Michelin tire companies in the late 1960s.