RADIAL TIRES

Tire is a ring-shaped part, either pneumatic or solid (including rubber, metals and plastic composites), that fit around wheels to protect them and enhance their function.

Radial tires - characteristics

Radial tires differ from traditional diagonal bias-ply tires in their construction, which minimizes tread wear and improves flexibility of the sidewall for better handling.

A radial tire is constructed differently. Rather than diagonal nylon plies that meet in the centerline it's made with polyester cords that run perpendicular from bead to bead, up over the face of the tire and down each sidewall. In other words it's "wrapped" at a right-angle to the direction of the tread. On the face of the tire over this polyester wrap, is a belt that runs below the tread. The belt is nearly the width of the tire and runs the circumference. This gives the tire a "squared" look. Though belts used to be made of rubber-coated fibers nearly all belts today are made from steel fibers. Hence the steel-belted radial. This belt helps stabilize the tread, reducing wear. Because of the construction of a radial tire, the sidewall will always have a bulge at the point of contact. Because of this bulge, when radial tires were still fairly new to the market many people assumed they were under inflated.

The history in brief

Charles Goodyear invented vulcanized rubber in 1844 that was later used for tires.

In 1888, John Dunlop invented the air-filled or pneumatic tires, however, his were for bicycles.

In 1895, André Michelin was the first person to use pneumatic tires on an automobile, however, not successfully.

In 1911, Philip Strauss invented the first successful tire, which was a combination tire and air filled inner tube. Strauss' company the Hardman Tire & Rubber Company marketed the tires.

In 1903, P.W. Litchfield of the Goodyear Tire Company patented the first tubeless tire, however, it was never commercially exploited until the 1954 Packard.

In 1904, mountable rims were introduced that allowed drivers to fix their own flats. In 1908, Frank Seiberling invented grooved tires with improved road traction.

In 1910, B.F. Goodrich Company invented longer life tires by adding carbon to the rubber. Goodrich also invented the first synthetic rubber tires in 1937 made of a patented substance called Chemigum.

Pneumatic Tyre (Tire)

John Boyd Dunlop (1840-1921) was a Scottish veterinarian and the recognized inventor of the first practical pneumatic or inflatable tyre/tire. His patent was for a bicycle tire, granted in 1888. However, Robert William Thomson (1822 - 1873) invented the actual first vulcanised rubber pneumatic tire. Thomson patented his pneumatic tire in 1845, his invention worked well but was to costly to catch on. Dunlop's tire patented in 1888 did, and so he received the most recognition. William Thomson also patented a fountain pen (1849) and a steam traction engine (1867).

Radial tires were invented in 1946 by Michelin, a French company, but were not widely used in the United States until the 1970s. Today all modern car tires are radial. In 2005, Michelin started to develop a tire and wheel combination, the Tweel, which does not use air.

Tire manufacturing

Pneumatic tires are manufactured according to relatively standardized processes and machinery, in around 450 tire factories in the world. Over 1 billion tires are manufactured annually, making the tire industry the majority consumer of natural rubber. Tire factories start with bulk raw materials such as rubber, carbon black, and chemicals and produce numerous specialized components that are assembled and cured. This article describes the components assembled to make a tire, the various materials used, the manufacturing processes and machinery, and the overall business model.

The tire is an assembly of numerous components that are built up on a drum then cured in a press under heat and pressure. Heat facilitates a polymerization reaction that cross-links rubber monomers to create long elastic molecules. These polymers create the elastic quality that permits the tire to be compressed in the area where the tire contacts the road surface and spring back to its original shape under high frequency cycles. Typical components are Inner liner, Body ply, Sidewall, Beads, Apex, Belt package, Tread and Cushion gum.

Manufacturing process is based on:

  1. Compounding and mixing

    Compounding is the operation of bringing together all the ingredients required to mix a batch of rubber compound. Each component has a different mix of ingredients according to the properties required for that component. Mixing is the process of applying mechanical working to the ingredients in order to blend them into a homogeneous substance.

  2. Component preparation

    Components fall into three classes based on manufacturing process - calendering, extrusion, and bead building. The extruder machine consists of a screw and barrel, screw drive, heaters, and a die. The extruder applies two conditions to the compound, heat and pressure. The extruder screw also provides for additional mixing of the compound through the shearing action of the screw. The compound is pushed through a die, after which the extruded profile is vulcanized in a continuous oven, cooled to terminate the vulcanization process, and either rolled up on a spool or cut to length. Tire treads are often extruded with four components in a quadraplex extruder, one with four screws processing four different compounds, usually a base compound, core compound, tread compound, and wing compound. Extrusion is also used for sidewall profiles and inner liners.

  3. Tire building

    Tire building is the process of assembling all the components onto a tire building drum. Tire Building Machines (TBM) can be manually operated or fully automatic. Typical TBM operations include the first stage operation, where inner liner, body plies, and sidewalls are wrapped around the drum, the beads are placed, and the assembly turned-up over the bead. In the second stage operation the belt package and tread are applied and the green tire is inflated and shaped.

  4. Curing

    Curing is the process of applying pressure to the green tire in a mold in order to give it its final shape, and applying heat energy to stimulate the chemical reaction between the rubber and other materials. In this process the green tire is automatically transferred onto the lower mold bead seat, a rubber bladder is inserted into the green tire, and the mold closes while the bladder inflates. As the mold closes and is locked the bladder pressure increases so as to make the green tire flow into the mold, taking on the tread pattern and sidewall lettering engraved into the mold. The bladder is filled with a recirculating heat transfer medium, such as steam, hot water, or inert gas. Temperatures are in the area of 350 degrees Fahrenheit with pressures around 350 PSI. Passenger tires cure in approximately 15 minutes. At the end of cure the pressure is bled down, the mold opened, and the tire stripped out of the mold. The tire may be placed on a PCI, or post-cure inflator, that will hold the tire fully inflated while it cools.

  5. Final finish

    After the tire has been cured, there are several additional operations. Tire Uniformity measurement is a test where the tire is automatically mounted on wheel halves, inflated, run against a simulated road surface, and measured for force variation. Tire balance measurement is a test where the tire is automatically placed on wheel halves, rotated at a high speed and measured for imbalance.

Type of tires

Solid tires

Solid rubber tires were introduced in 1881 on the wheels of hansom cabs in London. They were formerly used for many types of road vehicles, but they have now disappeared from highways owing to legislation that discouraged their use because they were hard on roads. The large sizes were supplanted by large pneumatic tires (truck and bus casings), but small solid tires came to be used extensively on industrial trucks and tractors and on carts. Solid tires are often adhered directly to the wheel or to a metal band applied to the periphery of the wheel.

Snow tires

Snow tires have an extra-deep tread for better traction on snow and ice. They are reputed to have 50 percent more pulling ability than regular tires on loosely packed snow and nearly 30 percent more on glare ice. In stopping on glare ice, however, snow tires have no advantage over regular tires; tire chains or studded tires are best for ice surfaces. Studded tires usually have about 100 studs tipped with tungsten carbide which contact the road as the tire rotates. Because of the damage they are said to cause road surfaces, they are prohibited in certain localities.

Run flat tires

A run-flat tire is a pneumatic vehicle tire that is designed to resist the effects of deflation when punctured, and to enable the vehicle to continue to be driven at reduced speeds (up to 90 km/h or 55 mph), and for limited distances of up to 100 miles (160.9 km), or even 200 miles (321.8 km) depending on the type of tire. First patented in 1892, run-flat tires were re-developed in 1978 and offered as an option in the 1990s mainly for two-seat sports cars with little room for spare tires and jacks. They have grown in popularity for other vehicles, such as high-end luxury cars, because of their safety and convenience, costing double the price of sports tires.

All-terrain tires

FAn All-terrain tire is a type of automotive tire most commonly found on Four wheel drive vehicles. The All-terrain tire is intended to provide a good compromise between off-road capability and on-road manners. Since manufacturers are aware of the fact that the majority of SUVs and other four wheel drive vehicles will never stray very far from public roads, the tires they are fitted with as standard tend to be biased towards road use. That is to say that for highway driving in a variety of conditions, they will offer good traction and low noise levels.

Spare tire

A spare tire is an additional tire (or tyre - see spelling differences) carried in a motor vehicle as a replacement for one that goes flat, a blowout, or other emergency. Spare tire is generally a misnomer, as almost all vehicles actually carry an entire wheel as a spare, as fitting a tire to a wheel is very difficult without specialised equipment, and is not practical in an emergency. However, spare tires (Donut type) are not meant to be driven long distances or most of them maximum speed is only 50 mph (80 km/h).

Maintenance

Tire maintenance for motor vehicles is necessitated by several factors. The chief cause of tire failure is friction from moving contact with road surfaces, causing the tread on the outer perimeter of tires to eventually wear away. When the tire tread becomes too shallow, the tire is worn out and should be replaced. The same wheels can usually be used throughout the lifetime of the car. Other problems encountered in tire maintenance include:

  1. Uneven or accelerated tire wear: can be caused by under-inflation, overload or bad wheel alignment.
  2. Increased wear on a tire facing the outside or the inside of a car: often a sign of bad wheel alignment.
  3. Tread worn away completely: especially when the wear on the outer rubber exposes the reinforcing threads within, the tire is said to be bald and should be replaced as soon as possible. Sometimes tires with worn tread are recapped, i. e. a new layer of rubber with grooves is bonded onto the outer perimeter of a worn tire. Since this bonding may occasionally come loose, new tires are considered superior to recapped ones.