Tire code

Automobile tires are described by an alphanumeric tire code (in American English and Canadian English) or tyre code (in British English, Australian English and others), which is generally molded (or moulded) into the sidewall of the tire. This code specifies the dimensions of the tire, and some of its key limitations, such as load-bearing ability, and maximum speed. Sometimes the inner sidewall contains information not included on the outer sidewall, and vice versa. The code has grown in complexity over the years, as is evident from the mix of SI and imperial units, and ad-hoc extensions to lettering and numbering schemes. New automotive tires frequently have ratings for traction, treadwear, and temperature resistance (collectively known as The Uniform Tire Quality Grade (UTQG) ratings). Most tires sizes are given using the ISO Metric sizing system. However, some pickup trucks and SUVs use the Light Truck Numeric or Light Truck High Flotation system. National technical standards regulations The European Tyre and Rim Technical Organisation (ETRTO) and the Tire and Rim Association (TRA) are two organizations that influence national tire standards. The objective of the ETRTO include aligning national tire and rim standards in Europe. The Tire and Rim Association, formerly known as The Tire and Rim Association of America, Inc., is an American trade organization which standardizes technical standards. In the United States, the Office of Vehicle Safety Compliance, a component of the Department of Transportation, is one of the agencies tasked to enforce the Federal Motor Vehicle Safety Standard (FMVSS). Canada has published tire regulations, such as the Motor Vehicle Tire Safety Regulations SOR 95-148. Explanation of tire codes Tire identification diagram The ISO Metric tire code consists of a string of letters and numbers, as follows: An optional letter (or letters) indicating the intended use or vehicle class for the tire: P: Passenger Car LT: Light Truck ST: Special Trailer T: Temporary (restricted usage for "space-saver" spare wheels) P indicates that the tire is engineered to TRA standards, and absence of a letter indicates that the tire is engineered to ETRTO standards. In practice, the standards of the two organizations have evolved together and are fairly interchangeable, but not fully, since the Load Index will be different for the same size tire. 3-digit number: The "nominal section width" of the tire in millimeters; the widest point from both outer edges (side wall to side wall). The tire surface that touches the road usually has smaller width. /: Slash character for character separation. 2- or 3-digit number: The "aspect ratio" of the sidewall height as a percentage of the nominal section width of the tire. If the information is...

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Snow tire

Snow tires—also called winter tires—are tires designed for use on snow and ice. Snow tires have a tread design with bigger gaps than those on summer tires, increasing traction on snow and ice. Such tires that have passed a specific winter traction performance test are entitled to display a "Three-Peak Mountain Snow Flake" symbol on their sidewalls. Tires designed for winter conditions are optimized to drive at temperatures below 7 °C (45 °F). Some snow tires have metal or ceramic studs that protrude from the tire to increase traction on hard-packed snow or ice. Studs abrade dry pavement, causing dust and creating wear in the wheel path. Regulations that require the use of snow tires or permit the use of studs vary by country in Asia and Europe, and by state or province in North America. Related to snow tires are those with an M+S rating, which denotes an "all-season" capability—quieter on clear roads, but less capable on snow or ice than a winter tire. Winter tire, showing tread pattern designed to compact snow in the gaps. Roadway conditions in winter Snow tires operate on a variety of surfaces, including pavement (wet or dry), mud, ice, or snow. The tread design of snow tires is adapted primarily to allow penetration of the snow into the tread, where it compacts and provides resistance against slippage. The snow strength developed by compaction depends on the properties of the snow, which depend on its temperature and water content—wetter, warmer snow compacts better than dry, colder snow up to a point where the snow is so wet that it lubricates the tire-road interface. New and powder snow have densities of 0.1 to 0.3 g/cm3 (6 to 20 lb/cu ft). Compacted snow may have densities of 0.45 to 0.75 g/cm3 (28 to 47 lb/cu ft). Snow or ice-covered roadways present lower braking and cornering friction, compared to dry conditions. The roadway friction properties of snow, in particular, are a function of temperature. At temperatures below −7 °C (20 °F), snow crystals are harder and generate more friction as a tire passes over them than at warmer conditions with snow or ice on the road surface. However, as temperatures rise above −2 °C (28 °F), the presence of free water increasingly lubricates the snow or ice and diminishes tire friction. Hydrophilic rubber compounds help create friction in the presence of water or ice. Dry and moist snow conditions on roadways Vehicle in cold, dry, powder snow, which offers comparatively better traction than moist snow. Vehicles in warm, moist, granular snow encounter decreased roadway traction. Treads Snow tire with metal studs,...

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Tire manufacturing

Pneumatic tires are manufactured according to relatively standardized processes and machinery, in around 455 tire factories in the world. With over 1 billion tires manufactured worldwide annually, the tire industry is the major consumer of natural rubber. Tire factories start with bulk raw materials such as synthetic rubber (60% -70% of total rubber in the tire industry), 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 and then cured in a press under heat and pressure. Heat facilitates a polymerization reaction that crosslinks rubber monomers to create long elastic. Inner liner The inner liner is an extruded halobutyl rubber sheet compounded with additives that result in low air permeability. The inner liner assures that the tire will hold high-pressure air inside, minimizing diffusion through the rubber structure. Body ply The body ply is a calendered sheet consisting of one layer of rubber, one layer of reinforcing fabric, and a second layer of rubber. The earliest textile used was cotton; later materials include rayon, nylon, polyester, and Kevlar. Passenger tires typically have one or two body plies. Body plies give the tire structure strength. Truck tires, off-road tires, and aircraft tires have progressively more plies. The fabric cords are highly flexible but relatively inelastic. Side Sidewalls are non-reinforced extruded profiles with additives to give the sides of the tire good abrasion resistance and environmental resistance. Additives used in sidewall compounds include antioxidants and antiozonants. Sidewall extrusions are nonsymmetrical and provide a thick rubber area to enable molding of raised letters. The sidewalls give the tire resistance against the environment. Sidewall plays an important role in strengthening of tire. Beads Beads are bands of high tensile-strength steel wire encased in a rubber compound. Bead wire is coated with special alloys of bronze or brass. Coatings protect the steel from corrosion. Copper in the alloy and sulfur in the rubber cross-link to produce copper sulfide, which improves bonding of the bead to the rubber. Beads are inflexible and inelastic, and provide the mechanical strength to fit the tire to the wheel. Bead rubber includes additives to maximize strength and toughness of tyres. Apex The apex is a triangular extruded profile that mates against the bead. The apex provides a cushion between the rigid bead and the flexible inner liner and body ply assembly. Alternatively called "filler" (as in the diagram above). Belt package Belts are calendered sheets consisting of...

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Tread

The tread of a tire or track refers to the rubber on its circumference that makes contact with the road or the ground. As tires are used, the tread is worn off, limiting its effectiveness in providing traction. A worn tire can often be retreaded. The word tread is often used casually to refer to the pattern of grooves molded into the rubber, but those grooves are correctly called the tread pattern, or simply the pattern. The grooves are not the tread, they are in the tread. This distinction is especially significant in the case of racing slicks, which have a lot of tread but no grooves. Tires Common tire tread pattern. Street tires The grooves in the rubber are designed to allow water to be expelled from beneath the tire and prevent hydroplaning. The proportion of rubber to air space on the road surface directly affects its traction. Design of tire tread has an effect upon noise generated, especially at freeway speeds. Generally there is a tradeoff of tread friction capability; deeper patterns often enhance safety, but simpler designs are less costly to produce and actually may afford some roadway noise mitigation. Tires intended for dry weather use will be designed with minimal pattern to increase the contact patch. Tires with a smooth tread (i.e., having no tread pattern) are known as slicks and are generally used for racing only, since they are quite dangerous if the road surface is wet. Street tires will also include wear limit indicators in the form of small raised bridges within the grooves. When the tread is worn down enough that the limit indicators make contact with the road, the tire is deemed to be at the end of its service life. Brake pads use similar indicators in the form of notches on their surface that disappear when they are used. Snow tires Snow tires or Winter tires are tires designed for use in colder weather, snow and ice. To improve traction, they are made of different rubber and have a different tread pattern from regular street tires. Off-road tires Studded mountain bike tires for use in icy conditions. Off-road tires used in mud or dirt feature individual knob patterns to allow the tire to bite into the surface and lever the sides of the tread to get a better grip. Given the smaller contact patch, these tires tend to wear quickly when used on asphalt. Mountain bike and motorcycle tires Mountain bike and some motorcycle tires feature tread similar to off-road tires used on cars and trucks but may sometimes include an unbroken tread that runs along its center. This feature provides better traction and lower noise on asphalt...

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Tire

A tire (American English) or tyre (British English; see spelling differences) is a ring-shaped component that surrounds a wheel's rim to transfer a vehicle's load from the axle through the wheel to the ground and to provide traction on the surface traveled over. Most tires, such as those for automobiles and bicycles, are pneumatically inflated structures, which also provide a flexible cushion that absorbs shock as the tire rolls over rough features on the surface. Tires provide a footprint that is designed to match the weight of the vehicle with the bearing strength of the surface that it rolls over by providing a bearing pressure that will not deform the surface excessively. The materials of modern pneumatic tires are synthetic rubber, natural rubber, fabric and wire, along with carbon black and other chemical compounds. They consist of a tread and a body. The tread provides traction while the body provides containment for a quantity of compressed air. Before rubber was developed, the first versions of tires were simply bands of metal fitted around wooden wheels to prevent wear and tear. Early rubber tires were solid (not pneumatic). Pneumatic tires are used on many types of vehicles, including cars, bicycles, motorcycles, buses, trucks, heavy equipment, and aircraft. Metal tires are still used on locomotives and railcars, and solid rubber (or other polymer) tires are still used in various non-automotive applications, such as some casters, carts, lawnmowers, and wheelbarrows. Stacked and standing car tires Tread pattern on a wheelbarrow tire Etymology and spelling The word tire is a short form of attire, from the idea that a wheel with a tire is a dressed wheel. The spelling tyre does not appear until the 1840s when the English began shrink fitting railway car wheels with malleable iron. Nevertheless, traditional publishers continued using tire. The Times newspaper in Britain was still using tire as late as 1905. The spelling tyre began to be commonly used in the 19th century for pneumatic tires in the UK. The 1911 edition of the Encyclopædia Britannica states that "he spelling 'tyre' is not now accepted by the best English authorities, and is unrecognized in the US", while Fowler's Modern English Usage of 1926 says that "there is nothing to be said for 'tyre', which is etymologically wrong, as well as needlessly divergent from our own older & the present American usage". However, over the course of the 20th century, tyre became established as the standard British spelling. History The earliest tires were bands of leather, then iron (later steel) placed on wooden wheels used on carts and wagons. The tire would be heated in a forge fire, placed over the wheel and quenched, causing the metal to contract and fit tightly on the wheel. A skilled worker, known as a wheelwright, carried out this work. John Boyd Dunlop on a bicycle c. 1915 The first patent for what appears to...

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