Goodyear tires generally contain a combination of natural rubber, harvested from a rubber tree, and synthetic rubbers made from oil and other ingredients. The particular blend of materials used for each tire is specific to the performance required of the tire. The blend consists of multiple rubbers and fillers mixed in large blenders and then milled. Goodyear has its own rubber company, which manufactures custom rubber blends; however, the exact ingredients and proportions of the blends are not published.
The natural rubber in the tires is created from liquid found in the trees' bark, which workers mix with acids to form solid rubber. Synthetic rubber is derived from polymers extracted from crude oil. Goodyear rubber manufacturers add carbon black, a powder formed by burning oil or a natural gas and creating soot, as well as sulfur and a mix of other chemicals in specifically crafted ratios, to create the finished product: a tire comprised of over 30 materials.
Goodyear adds auxiliary chemicals for functions such as protecting the tire from ultraviolet rays and keeping the rubber flexible while workers shape it. Other chemicals are added for specific capabilities such as high friction and low friction. The ratios of the chemicals and rubber types also help determine the threading of the tires, which differs according to the type of vehicle, season and usage.