8 Steps to Making a Tire:

1.  Mixing of the raw materials:  Materials are all mixed to form a rubber compound.

Large quantities of natural and synthetic rubber, carbon black, sulfur, and other chemicals and oils are stored until needed.  The manner in which these materials are stored and transported could lead to one of the materials not being appropriate for the mixing process or tainted.  Computer control systems contain recipes for mixing the ingredients and can automatically measure out specific batches of rubber and chemicals for mixing depending on the specific type or variation of tire needed.  Gigantic mixers are used to stir the rubber and chemicals together in batches.

2. Each mix is remilled with additional heating to soften the batch and mix

additional chemicals.  The batch goes through a mixer again with additional chemicals being added to form what is known as the final mix.  Heating and friction are applied to the batch to soften the rubber and evenly distribute the chemicals.  There are different chemical compositions for the body, bead, and tread of the tire.

3. The final mix of rubber then goes through powerful rolling mills that squeeze the

batch into thick sheets of rubber.  These sheets are used to make the specific parts of the tire.  Each strip of rubberized fabric is used to form a layer called a “ply” in the tire body.  Some tires may have as many as 4 to 6 “plies” to for a tire body.

4. To form the beads of a tire, wire bundles are formed on a wire-wrapping machine.

These wire bundles are made or shaped into a ring that is eventually covered by rubber.

5. Rubber to make the tire tread and sidewalls go from the batch mixer to another

type of processing machine called an extruder.   This machine mixes and heats the batch and it is then forced out through a die (a shaped opening) to form a layer of rubber.  Think of your childhood play dough machines.  Sidewall rubber is covered with a protective plastic sheet and rolled.  Tread rubber is sliced into strips and loaded into large, flat metal cases called “books.”

6. The rolls of sidewall rubber, the books containing tread rubber, and the racks of

beads are all delivered to an assembler (employee) at a tire-building machine.  The machine consists of a collapsible rotating drum that holds the tire parts together.  The assembler starts building the tire by wrapping the rubber covered fabric plies of the body around the machine drum.  After the ends of the plies are connected with glue or sealant, the beads are added and locked into place with additional tire body plies placed over the beads.  Special power tools are used by the assembler (employee) to shape the edges of the tire plies.  The extruded rubber layers for the sidewall and the tread are glued or sealed into place.  The assembled tire (“Green Tire”) is removed from the drum and taken out of the machine.  Often a “Green Tire can be left sitting for a period of time before being cured, which may cause bubbles of air space in the tread, sidewall or interior.  These types of things can easily lead to a tire failure and serious injury after the tire has been used and traveling at highway speeds.

7. The “Green Tire” is placed inside a large tire mold for the curing process.  This

mold looks like a giant metal oyster that opens.  Inside the mold is a flexible balloon called a bladder.  The green tire is placed over the bladder and the mold closes.  The bladder fills with steam that heats the tire causing it to expand and shape the tire and force the tread rubber against the raised interior of the mold.   How long the green tire spends in the mold depends on the characteristics of what type of tire is needed.

8.   After the tire has been cured it is then removed for cooling and quality testing.  Each tire is thoroughly inspected for flaws.  Bubbles, or air space in the rubber of the tread, sidewall or interior is one specific flaw that is looked for.  After the visual inspection, the tire is placed on a test wheel where it is inflated and spun.  Sensors in the test wheel measure the balance of the tire and determine if the tire runs in a straight line.  Finally the tire is moved to a warehouse for distribution.