Background

A tire is a rubber casing that attaches to the wheel’s rim. It is strong and flexible. Tires are a rubber casing that attaches to the rim of a wheel. They provide traction and cushion. Tires can be found on vehicles and trucks, buses and aircraft landing gear. They also come on industrial vehicles like forklifts and common conveyances like baby carriages and shopping carts.

Pneumatic tires are used for most vehicles. The tire holds air under pressure. Pneumatic tires used to have an inner tube that held the air pressure. However, the tire is now designed to seal the pressure with the wheel’s rim.

The pneumatic tire with inner tube was invented by Robert Thomson, a Scottish inventor. However, his design was far ahead of its time and received little attention. John Boyd Dunlop, another Scotsman, invented the pneumatic tire in 1880s. It was immediately adopted by bicyclists.

Although natural rubber is the most common raw material for tires manufacturing, synthetic rubber can also be used. To achieve the right properties of strength, resilience, wear resistance, and durability, rubber must first be treated with various chemicals, then heated. The process of strengthening rubber was discovered by Charles Goodyear, an American inventor. It is also known as vulcanization or curing by accident. Although he had been working with rubber since 1830, he was unable to create a suitable curing process. Goodyear tried a mixture of india rubber, sulfur and put it on a hot stove. The rubber-sulfur combination formed a hard lump instead of melting. This chemical reaction caused the mixture to form a solid lump. He continued to experiment until he was able to treat continuous sheets.

Large, modern factories employing skilled workers and produce over 250 million tires annually. While automation automates many steps of the manufacturing process, skilled workers still need to assemble components of a tire.

Raw Materials

Natural and synthetic rubber can be used to make tires. Rubber is the main raw material for tire manufacturing. The bark of Hevea Brasiliensis, a rubber tree, contains natural rubber as a milky liquid. The liquid latex is mixed in acid to make the raw rubber for tire manufacturing. The rubber is then pressed to remove excess water. After drying, the sheets are pressed into huge bales and shipped to tire factories all over the world. The polymers in crude oil are used to make synthetic rubber.

Carbon black is the other main ingredient in tire rubber. Carbon black is a fine powder made from crude oil and natural gas. It is created by incomplete combustion of the fuel, which results in a lot of fine soot. It is necessary to produce so much carbon black that railroad cars transport it. Large silos store it at the tire factory until it’s needed.

Tires can also be made from sulfur and other chemicals. When certain chemicals are mixed with rubber, they create specific tire characteristics, such as high friction but low mileage for a racing tire and high mileage (but lower friction for a passenger car tires). While rubber is being formed into tires, some chemicals help to keep it flexible. Other chemicals protect rubber from ultraviolet radiation.

Design

The tread, the body with sidewalls and the beads are the main components of a passenger car tire. The tread is the raised pattern that comes in contact with road. The tire’s specific shape is created by the body, which supports the tread. The rubber-covered, metal wire bundles of beads hold the tire onto the wheel.

The role of computer systems in tire design is now important. Tire engineers can simulate tread design performance and other parameters using complex analysis software that uses years of test data. The software generates a 3-D color image of possible tire designs and calculates the impact of different stress levels on the tire design. Tire manufacturers save money by using computer simulations to discover design limitations before the prototype tire is assembled and tested.

Computers can simulate the effects on different rubber compounds, in addition to testing tread design and tire body construction. There may be twenty types of rubber in a passenger car tire. For example, one rubber compound can be used in the tread to provide good traction in cold conditions; another compound is used for increased rigidity on the tire sidewalls.

Tire engineers have completed computer studies to design a new tire. Manufacturing engineers and skilled tire assemblers then work together with the designers to create prototypes for testing. Tire factories can begin mass production once design and manufacturing engineers have approved a new design.

The story of tires is a great example of how innovation in one industry can lead to major changes in another. Simply put, the “take off” of the automobile industry changed the American rubber industry during the first decade of the 20th century. In the late nineteenth century, rubber was primarily focused on making footwear, bicycles and carriage tires. In the eyes of the general public, rubber and automobile tires had become almost synonymous by World War I. 72,000 new cars were sold in 1901, with 28,000 tires being original equipment (OE), and 68,000 replacement tires. With tires accounting for about half of all rubber sales by 1918, OE tire sales had exceeded four million. Total tire production was 24.5 million.

The emergence of well-known companies like Goodyear, Goodrich and Firestone was accompanied with a huge increase in production. Also, the industry’s central office in Akron, Ohio was created. While employment rose, productivity increases were only possible with the help of technology. The mechanization of core construction was the fundamental innovation. Workers used to stretch, cement, and then stitch each ply around an iron core to make tires. W. C. State of the Goodyear Company in 1909 patented a machine that could carry the tread on rollers and the beads on the central turret. While the machine’s electric motor maintained the correct tension, the worker was able to cement and stitch while the worker pulled the material over the core. While skill and dexterity were still important, the core-building machine simplified the process and increased production by between six and eight tires per worker per day to twenty to forty tires per day depending on the type.

William S. Pretzer

The Manufacturing
Process

The tire-forming machine wraps multiple layers of rubber around a rotating metal drum to make a passenger car tire. The various components of the tire are brought to the tire-forming machine where a skilled assembler cuts the strips and positions them to form the various parts. This is called a “green” tire. The metal drum will collapse when a green tire has been completed. This allows the tire assemblers to take the tire out. The mold is used to cure the green tire.

• 1. The first step in tire manufacturing is mixing raw materials to create the rubber compound. Railcars transport large amounts of synthetic and natural rubber, carbon black and sulfur. All of these chemicals and oils are kept until they are needed. Computer control systems can use different recipes to automatically measure specific batches of rubber or chemicals for mixing. Hanging like vertical cement mixers and giant mixers, these mixers mix the rubber with chemicals in large batches that weigh up to 1,100 pounds.
• 2 The mix is then remilled using additional heating to soften it and mix the chemicals. The batch is then put through a second mixer, where additional chemicals can be added to make the final mix. To soften and distribute chemicals evenly, heat and friction are used to mix the three stages. Each tire part determines the chemical composition of the batch. Certain rubber formulas are used to make the tires, while others are used to make the beads and tread.

Body, beads, and tread

• After a rubber batch has been mixed, it is sent through powerful rolling mills to be rolled into sheets. These sheets can then be used to create the parts of the tire. For example, the tire body is made up of strips of cloth-like fabric, which are then covered with rubber. Each piece of rubberized fabric is used for forming a layer known , a ply in the tire body. An average passenger car tire can have up to four plies.
• 4 Wire bundles are made on a wire wrapping machine for the beads of tires. The wire bundles are then shaped into rings and covered with rubber.
• 5. The rubber for the tire treads and sidewalls is transported from the batch mixer into an extruder. The batch is heated, mixed further and then forced through a die to form a layer. The sidewall rubber is wrapped in a protective sheet of plastic and rolled. Sidewall rubber is covered with a protective plastic sheet and rolled.

Tire-building machine

• 6 Tire-building machines are equipped with a skilled assembly crew that can deliver the rolls of sidewall rubber, books containing tread rubber and racks of beads. The machine’s center is a rotating drum that can collapsible hold the parts of the tire. The machine drum is used to hold the tire parts. The ends of the fabric plies are joined using glue. Next, the beads are attached and secured with additional tire body plies. The tire assembler then shapes the tire plies’ edges using special power tools. The tread and sidewall rubber layers are then glued together and the tire is removed from the tire-building machine.

Curing

• 7 For curing, a green tire is placed in a large mold. The tire mold looks like a huge, metal clam that opens to reveal a large flexible balloon known as a bladder. As the clamshell mold closes the bladder, the green tire is placed on top. The bladder expands and forms the tire, forcing the rubber tread against the raised mold. The steam heats up the green tire to 280° during curing. The characteristics of the tire determine the time it takes to cure in the mold.
• 8 The tire is taken out of the mold after curing has been completed. It is then allowed to cool and tested. Every tire is carefully inspected for any flaws, such as cracks in the rubber, sidewall or interior. Next, the tire is placed onto a test wheel and inflated before being spun. The test wheel has sensors that measure the balance of each tire to determine if it runs straight. A modern tire is rarely rejected because of its design and construction. After the tire is inspected and tested, it’s moved to a warehouse where it will be distributed.

Quality Control

The suppliers of raw materials are the first to be held responsible for quality control. A tire manufacturer today seeks suppliers that test raw materials before they are shipped to its plant. A few suppliers will provide detailed certification about the composition and properties of raw materials. Manufacturers often have special purchasing agreements. Tire company chemists test the raw materials at random as they arrive to ensure that suppliers are certified.

Samples of rubber are taken during batch mixing to verify different properties like tensile strength or density. The tire components are the responsibility of each tire assembler. Plant managers can track specific components and rubber batches using code numbers and a complete computer record-keeping system.

For destructive testing, hundreds of tires are removed from the assembly line when a new design of tire is being made. For example, some tires are cut open to inspect for air pockets between the body plies. Others are then pressed on metal studs for puncture resistance. Other tires are spun quickly and forced onto metal drums in order to determine their performance and mileage.

Tire quality control can also be done using a variety of non-destructive techniques. The X-ray videography gives a quick and clear view of a tire. A tire is randomly selected for an Xray tire test. It is then taken to a radiation booth and bombarded with Xrays. The X-ray image is displayed on a screen by a technician, which allows for easy identification of tire defects. Manufacturing engineers will review each step of the tire component assembly in order to identify the source of the defect.

To identify potential process improvements, we also use feedback from tire dealers and consumers.

The Future

New tires are constantly improving in tire design and rubber chemistry, resulting in exciting new tires with better performance in extreme weather conditions and greater mileage. Tires can last for up to 80,000 miles, according to manufacturers. Computer-tested treads now have unique asymmetrical bands that provide better traction on snowy or wet roads.

Non-pneumatic tires are another option for tire designers. They don’t have air under pressure and can’t go flat. A non-pneumatic tire can be described as a single slab of thick plastic attached directly to the wheel rim. The plastic curves from the rim until it reaches a point where a rubber tire is attached to the plastic. This tire has a larger contact area between the tread and the road, which results in lower rolling resistance and better handling.