The incredibly hands-on process of building our tires always captivates curious car enthusiasts. Take an inside look at a classic bias-ply whitewall as it goes through the manufacturing process. These handcrafted tires are mounted on anything and everything including hot rods, rat rods and concours-quality stock restorations.
Tire Production Video Transcript:
Coker Tire’s method of tire manufacturing is second to none in the collector vehicle market, and yields fantastic results. It’s a very labor-intensive process, and each tire requires special attention from start to finish.
The making of a whitewall tire begins with the raw materials, consisting of natural and synthetic rubber, along with various chemicals and curing agents. These materials are loaded onto a conveyor belt, where they are delivered to the mixer, and brought up to a specified temperature during the mixing process.
From there, the rubber moves along the belt to a mill, where it is formed into a sheet, which measures 40 inches wide by 3/8-inch thick. The sheet is cooled, and a technician labels it for use in a certain part of the tire. Specific pieces are used for various applications within the tire construction, so this is vital to tire strength and stability. The sheets are then sent to a calendar, which is a piece of machinery that applies the rubber to nylon or polyester fabric to create the ply layers. By squeezing the rubber sheet and a layer of fabric between steel rollers, the technicians can determine the final thickness of the material.
The sheet then goes to a cutter, which allows the operator to precisely cut it to the desired length, width and angle before it is rolled into a liner and sent to the tire building machine. As the trimmed sheet of rubber moves down the assembly line, its final destination is the tire-building drum, where the first form of assembly can be performed. The number of rubber sheets used determines the tires load rating, but the majority of passenger car tires feature a four-ply construction. In the early years of tire manufacturing, cotton was used in the ply sheets, but it is now common to use nylon or polyester.
Bundles of steel wire are placed in a bead former, which coats each strand of wire with rubber, so it will adhere to the rest of the tire. This creates a bead bundle and the number of wire strands is dependent on the size and load range of the tire. The bead bundles are placed on either end of the tire-building drum, where the ply edges are turned up around the bead bundle and locked into place.
Tire assembly continues with a different type of rubber sheet, which is sent to the mill room, where the heated rubber travels through a die. This forms the rubber into a contoured component, to be used for the tread and sidewall of the tire. At this time, white rubber sheet is applied to the sidewall material. The contoured rubber is very hot and needs to be cooled quickly to keep the correct consistency. This extrusion is cut to a specified length, and then applied to the ply layers that were already installed on the tire-building drum. When the completed tire structure is removed from the drum it is called a “green tire”.
The Green Tire is then loaded into a specific mold, which rests inside of a curing press. The mold determines the tires tread pattern, sidewall reveals, brand names and DOT information. The molds are sometimes carried over from discontinued tires, but they are always refurbished to today’s standards, even if the original mold is many years old. The tire mold serves two purposes: it gives the tire its final shape and it also cures the rubber. Each mold features a curing bladder, which is inflated by steam and pushes the hot rubber out into the mold details. During the curing process, the rubber reaches 360 degrees Fahrenheit.
When the curing process is complete, the tire has its distinct shape, size and details, but it still needs some more work to reach completion. The tire is inflated on a special wheel and allowed to cool, and then sent to its final inspection area. When the tire passes inspection, it continues its path to the buffing area. Buffing is required on most whitewall tires, to clean off any black rubber that bleeds over during the construction process. A special attachment, based on the whitewall width, lightly buffs the sidewall of the tire so that the whitewall is clean and white. It is then protected with a blue coating that keeps the whitewall from being damaged in transit, before being wrapped in plastic and sent into the warehouse for shipping.
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