We see them by the hundreds and thousands, every day. As the component that connects a vehicle to the road, tires are vitally important in providing traction, performance, handling and safety. But what actually happens when the tire is manufactured? The process will differ for various types of tires as well as between manufacturers. Check out the video below from Michelin to see how they make their tires:
It all starts with rubber. Whether natural or synthetic, the rubber that is used to bond the tire’s various parts together is mixed with oils and additives to help it bond the different parts together. The exact composition depends strongly on the tire’s end use. If a tire is meant to improve performance, it will have a different composition than a tire intended for bad weather conditions. If it is a winter tire, the rubber compound will be softer than that which is used for summer tires. It can also vary depending on what part of the tire is being created, with some butyl and halogenated butyl rubbers holding the air inside the tire’s lining layer. The different components for the rubber are mixed and once it’s near the consistency of chewing gum, it’s time to start making parts.
Once the rubber has been mixed to the right consistency, it’s brought to the different presses and machines to form the tire’s components. Starting out as a solid sheet known as a slap, it is at this point that the rubber begins to take on different qualities based on its end purpose. This can include the rubber-coated steel bead that attaches the tire to the wheel, the extruded sidewalls and tread, the fabric or steel belts being incorporated into the tire, the inner liner and the plies. Once these components are complete, it’s time for the tire machine.
Now that all the components have been formed, they’re assembled in a machine known as a tire building machine. After all the parts are laid in place in the machine, they are pressed together to form a tire in what is typically a two-step process. A drum is used to assemble the tire, creating a base on which the inner liner is wrapped, followed by the plies and the bead assemblies. A bladder then inflates, making the body plies turn up and join the bead, at which point the sidewalls are pressed into place. After this stage, the belts, nylon cap and tread are placed on top of the first stage. But it’s not ready for the road yet. Known as a “green” tire, the tire still needs to undertake a curing process which also puts the tread pattern onto the tire.
The green tire is placed in a mold which will help determine its final shape and what tread pattern it will have. Once the tire is in place, it is inflated until it is pressing against the sides of the mold. The mold is then heated to 300º F and it cures for a set period of time. For smaller passenger car tires, this can be as short as 15 minutes, but for larger tires, the process can take one day or more to complete. This process is known as vulcanization.
The next step for the newly-cured tire is inspection. Each tire is carefully checked to make sure it will perform as advertised and that it doesn’t have any faults such as bubbles that may cause it to fail and compromise the safety of the vehicle’s passengers.