<P> In 1946, Michelin developed the radial tire method of construction . Michelin had bought the bankrupt Citroën automobile company in 1934, so it was able to fit this new technology immediately . Because of its superiority in handling and fuel economy, use of this technology quickly spread throughout Europe and Asia . In the U.S., the outdated bias - ply tire construction persisted, with market share of 87% as late as 1967 . Delay was caused by tire and automobile manufacturers in America "concerned about transition costs ." In 1968, Consumer Reports, an influential American magazine, acknowledged the superiority of radial construction, setting off a rapid decline in Michelin's competitor technology . Even in the U.S., the radial tire now has a market share of 100% in automobiles . </P> <P> Today, over 1 billion tires are produced annually in over 400 tire factories (see List of tire companies). </P> <P> There are two aspects to how pneumatic tires support the rim of the wheel on which they are mounted . First, tension in the cords pull on the bead uniformly around the wheel, except where it is reduced above the contact patch . Second, the bead transfers that net force to the rim . </P> <P> Air pressure, via the ply cords, exerts tensile force on the entire bead surrounding the wheel rim on which the tire is mounted, pulling outward in a 360 degree pattern . Thus the bead must have high tensile strength . With no force applied to the outer tread, the bead is pulled equally in all directions, thus no additional net force is applied to the tire bead and wheel rim . However, when the tread is pushed inward on one side, this releases some tension in the corresponding sidewall ply pulling on the bead . Yet the sidewall ply on the other side continues to pull the bead in the opposite direction . Thus the still fully tensioned sidewall ply pulls the tire bead and wheel rim in the same direction as the tread displacement with equal force as that applied to push the tread inward . </P>

Where does the rubber in a tire come from