Tires are essential to any vehicle. As the only piece that touches the road, a tire needs to provide a comfortable balance of traction, durability, and comfort. Otherwise, driving becomes more dangerous not only to the car, but to the passengers inside as well. Many factors go into how tires are made in order to achieve this balance. This guide provides an introduction to these steps.
Rubber is the most notable raw material that goes into tire manufacturing, with both natural and synthetic rubber used in the solution. The rubbers are combined with carbon black, sulfur, and other chemicals and stirred together in giant mixers. Every mix goes through three stages where heat and friction are applied to ensure that the rubber is softened and the chemicals are evenly distributed.
The Machine Process
After the mixing is completed, the solution—sometimes called a “web”—goes through a series of rollers that squeeze it into sheets, divide those into strips, and ensure a constant width control. Every strip forms a layer in the tire’s body, called a “ply.” The “beads”—wire bundles that hold the tire in place—are formed by running wire bundles through a wire-wrapping machine and coating those with rubber. The batch for the tread (which comes into contact with the road) and the sidewalls (which support the tread and give the tire its shape) are run through an extruder, which mixes and heats the batch even further and forces it out through a shaped die to form a layer of rubber. All of these pieces come together at a tire-building machine where the plies are glued together around the machine drum at the center, the beads are locked into place with additional plies, the plies’ edges are shaped with special power tools, and the layers from the sidewalls and tread are glued together, resulting in what is referred to as a “green tire.”
The final step in how tires are made involves placing the green tire in a mold that gives it its eventual shape. The green tire is placed over a “bladder”—a large, flexible balloon that fills with steam and expands to form the shape and run the tread against the mold’s interior, which explains why you see those ridges alongside it. Temperatures from the steam can reach up to 280 degrees. Once the curing process is finished, the tire is cooled off and inspected for any bubbles or other issues with the rubber. Finally, the tire is spun on a test wheel with sensors that measure its balance and determine whether it will run in a straight line. If the test is successful, the tire is sent to a warehouse for distribution to the supplier.