How a Tire is Made

As many as two hundred different raw materials combine into a unique mix of chemistry, physics & engineering to give consumers the highest degree of comfort, performance, efficiency, reliability & safety modern technology & creativity can provide. Here are the basic steps:

Planning & Design

Many tires are custom-designed to meet the stresses & performance needs specified by the maker of a particular model vehicle. The process begins with a computer, which converts the mathematics of the car's special needs into specifications. A prototype tire is then made to test the tire design's ability to provide the desired characteristics. Custom-designing a tire for a particular vehicle typically takes many months of testing, inspection, & quality checks by the tire maker & the vehicle maker. Only then does the vehicle maker commit with an order.

Manufacturing

The production process begins with the selection of several types of rubber along with special oils, carbon black, pigments, antioxidants, silica, & other additives that will combine to provide the exact characteristics wanted. Separate compounds are used for different parts of the tire. A machine called a banbury mixer combines the various raw materials for each compound into a homogenized batch of black material with the consistency of gum. The mixing process is computer-controlled to assure uniformity. The compounded materials are then sent to machines for further processing into the sidewalls, treads or other parts of the tire.

Then the task of assembling the tire begins. The first component to go on the tire building machine is the innerliner, a special rubber that is resistant to air & moisture penetration & takes the place of an inner tube. Next come the body plies & belts, which are often made from polyester & steel. Plies & belts give the tire strength while also providing flexibility. The belts are cut to the precise angle & size the tire engineer specifies to provide the desired ride & handling characteristics. Bronze-coated strands of steel wire, fashioned into two hoops, are implanted into the sidewall of the tires to form the bead, which assures an airtight fit with the rim of the wheel. The tread & sidewalls are put into position over the belt & body plies, & then all the parts are pressed firmly together. The end result is called a "green" or uncured tire.

The last step is to cure the tire. The "green" tire is placed inside a mold & inflated to press it against the mold, forming the tread & the tire identification information on the sidewall. Then it is heated at more than 300 degrees Fahrenheit for twelve to fifteen minutes, vulcanizing it to bond the components & to cure the rubber. (FACT: This twelve to fifteen minute curing process is for passenger & light truck tires only, off-road & large tires may take up at a day to cure because of their size!) Every tire is then inspected, & sample tires are randomly taken from the line & tested. Some are x-rayed, some are cut apart to look for flaws, others are run on test wheels, or road-tested to evaluate handling, mileage & traction performance.