How to Make Rubber Tires

Tires are made in layers.

The exact manufacturing process used to create rubber tires is each manufacturer's closely guarded secret. Since tires are used under conditions of high speed and high pressure, they should not be made by amateurs. The modern rubber tire has only been in use for a century, despite the revolutionary vulcanization process, (where a heated rubber and sulfur mixture created rubber that was resistant to heat and cold). The process was discovered in 1839 by Charles Goodyear, who decades later, had a tire company named in his honor.

Things You'll Need

• Synthetic rubber
• Carbon black
• Sulfur
• Zinc oxide
• Steel belt wires coated with brass
• Gauge and halobutyl
• Steel bead wire
• Banbury Mixer
• Calendering machine
• Vulcanization machine
• extruder

Instructions

1. Create a rubber mixture with up to ten different ingredients in a Banbury Mixer, depending on what finish you want for the tire. An average tire is made of 27 percent synthetic rubber. The remaining tire mixture can be made up of sulfur, carbon black and zinc oxide, for example. Carbon black is a filler that creates the black skid mark left on the road when a tire squeals and makes up 28 percent of an average tire by weight. Sulfur helps cure the rubber into a form resistant to temperature extremes, and zinc oxide is a pigment to help color the tire.

2. Mix the rubber and the added ingredients mechanically in the Banbury Mixer until the mixture becomes homogeneous (uniform).

3. Form the homogeneous rubber into slabs by using a mechanical extruder. The rubber can be used to coat steel or fabric cords, which will make up part of the tire by passing the cords and rubber through a calendering machine. Alternatively, the rubber slabs can be used as tread or sidewall components of the tire.

4. Calender an inner liner from gauge and halobutyl with rubber. Wrap the inner liner with bead wire, steel bead reinforcing strips and the rubber sidewalls.

5. Roll calendered steel wires around the inner section and apply fabric overlays and steel wire belts. Attach the extruded tread using cement to a layer of steel wires, cut the tread length to size and apply cement to both ends to stick them together.

6. Vulcanize the tire by inserting it into a vulcanization mold, stamped with the tire tread pattern. Use the inflatable rubber bladder, pressurized with steam or hot water, inside the vulcanization machine to press the tire against the moldings.

Tips & Warnings

• Tires are subject to Department of Transportation standards and tires that have not been made to DOT standards should never be used.

References

• Orings: How to Make Tires
• Tire Failures: White Paper
• Mindfully: Tire Production
• National Highway Traffic Safety Administration: Tire Safety