How tires are made

A tire is a cake of rubber, steel cord and fabric, assembled flat and then pressed into its tread in a hot mold.

stations: 8
things upstream: 63
raw sources: 22
steps from the ground: 7

The short version

A car tire starts as batches of synthetic and natural rubber blended with carbon black. Separate machines make the tread, the fabric plies and the steel bead rings. A builder wraps them around a drum into a soft, shapeless tire. A hot mold then presses in the tread pattern while the rubber cures into a springy solid.

Blend the rubber compounds

Rubber is worked together with carbon black, silica and other chemicals until the batch is uniform. The most common rubber is a styrene-butadiene copolymer, and each part of the tire gets its own recipe, from a grippy tread to a flexible sidewall.

Goes in
Synthetic rubber Natural rubber latex Carbon black Sulfur
Wrap the bead wire

Steel cables are bundled into rings and sheathed in hard rubber. These rings are the beads. They grip the wheel rim and keep the air from escaping where tire meets metal.

Goes in
Steel wire
Brass-coat the steel cords

Steel cords get a thin layer of brass, which helps rubber stick to them. Rubber that lets go of its cords is a tire that comes apart.

Goes in
Steel wire Brass
Press cords into rubber sheets

Rollers squeeze rubber on both sides of rows of parallel cords, making wide sheets called plies. In a radial tire the cords run straight across from bead to bead. Further steel-reinforced belts sit under the tread to stabilize it.

Goes in
Nylon Polyester
Squeeze out the tread

Warm tread rubber is pushed through a shaped die in one long ribbon, then cut to the length of one tire's circumference.
Build the raw tire

A building drum collects the inner liner, plies, beads, belts, sidewalls and tread in order. The result is a soft, tacky tire, with no tread pattern yet, that holds together only by stickiness.
Cure it in a hot mold

The raw tire goes into a heated mold that presses the tread grooves and the sidewall lettering into the rubber. Heat sets off vulcanization, and the sticky rubber becomes elastic and durable.
Trim, test and inspect

Vent spurs are trimmed off and every tire is checked by eye and by machine. Samples face harder tests for uniformity and strength.

End of the lineTire Next it goes into car, electric car, bicycle and 1 more.

Worth repeating

The LEGO Group made over 318 million toy tires in 2011, which Guinness World Records recognized as the highest annual tire production by any manufacturer.
A passenger vehicle uses roughly 5 to 15 percent of its fuel just overcoming rolling resistance in its tires.
John Boyd Dunlop built the first practical pneumatic tire in 1888, partly to ease the headaches his 10-year-old son Johnnie suffered while riding.