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device made of rubber and fabric and attached to the outer rim of a vehicle wheel. Solid rubber tires were in limited use before 1850; they are still used in some special applications, e.g., for industrial trucks in factories. The pneumatic rubber tire uses rubber and enclosed air to reduce vibration and improve traction. It was first patented by Robert W. Thomson, a Scottish civil engineer; however, it was not a commercial success until the Scottish inventor John Dunlop patented a pneumatic bicycle tire in 1888 and started a tire company.

The main parts of a modern pneumatic tire are its body, tread and sidewalls, and beads. The body is made of layers of rubberized fabric, called plies, that give the tire strength and flexibility. The fabric is made of rayon, nylon, or polyester cord. Covering the plies are sidewalls and tread of chemically treated rubber. The sidewalls form the outer walls of the tire. The tread is a thick hoop of rubber that comes into direct contact with road surfaces. To improve its traction, the tread has patterns of deep and shallow grooves and channels, depending on the intended use, and also may have protruding metal studs for icy or snowy conditions. High-performance tires have treads optimized for warm weather, and winter (or snow) tires are optimized for cold and snow; all-season tires are general-purpose tires. Imbedded in the two inner edges of the tire are steel hoops, called beads, that hold the tire to the wheel rim.

In the older type of pneumatic tire, air is sealed in an inner tube of butyl rubber beneath the body. In a tubeless tire the seal between the beads and the wheel rim is airtight and the underside of the tire body is coated with butyl rubber to keep the air from escaping. A puncture in a tire leads to loss of air and a so-called flat tire. Self-sealing tires are lined with a rubber or rubberlike compound that, when the tire is punctured by a slim object, such as a nail, coats the object and seals the hole to prevent air from escaping. A recent innovation is the run-flat tire. In the most common version, the sidewall is reinforced so that, in case of a large puncture and a total loss of air pressure, the tire is self-supporting; the vehicle can continue operating as if there were no tire problem for up to 125 mi (200 km). An innovative bead design keeps the tire securely on the rim. Such tires are often linked to a pressure monitoring system that alerts the vehicle operator to the puncture.

The most important feature of tire design is the arrangement of the cord, or ply. The three main types are bias ply, radial-ply belted, and bias-ply belted. In a bias-ply tire the cords in a single ply run diagonally from the beads on one inner rim to the beads on the other. However, the orientation of the cords is reversed from ply to ply so that the cords crisscross each other. In a radial-ply (also called radial-ply belted) tire the cords in every ply run perpendicularly from the beads on one inner rim to the beads on the other, and there is a rigid belt, usually of fine steel wire, between the tread and the plies. This construction provides longer tread wear but a rougher ride. In a bias-ply belted tire the cords in the plies are aligned as in a bias-ply tire, but a rigid belt, usually of synthetic fabric, is added. This tire has longer tread life than a bias-ply tire and provides a more comfortable ride than does a radial-ply tire.

Pneumatic tires are made in a variety of sizes to accommodate a variety of vehicles. The size is usually expressed by a standardized code of the form Axxx/yyBzz, where A designates the type of vehicle the tire is made for, such as P (passenger) or LT (light truck); xxx denotes the tire width in millimeters; yy denotes the aspect ratio (the ratio of the tire's height to its width); B is an R if the tire is of radial-ply construction; and zz is the wheel-rim diameter in inches. In addition, an alphabetic speed rating and a numeric tread-wear rating are embossed on the outer wall of the tire. Most tires are of the balloon type, with a large cross section and thin sidewalls. The large size permits a low inflation pressure, and the increased tread area gives better traction and braking qualities. Excessive tire wear is caused by incorrect inflation, wheel misalignment, sudden braking, and high speeds.

The Columbia Electronic Encyclopedia™ Copyright © 2013, Columbia University Press. Licensed from Columbia University Press. All rights reserved. www.cc.columbia.edu/cu/cup/
The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.



a city in western Turkey, in the vilayet of Izmir. Situated in the valley of the Kücük Menderes River. Population, 28,000 (1970). Tire has a railroad station. It is a trade center for cotton, tobacco, and figs. Emery and mercury are mined nearby.

The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.


A continuous metal ring, or pneumatic rubber and fabric cushion, encircling and fitting the rim of a wheel.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.


(US), tire
1. a rubber ring placed over the rim of a wheel of a road vehicle to provide traction and reduce road shocks, esp a hollow inflated ring (pneumatic tyre) consisting of a reinforced outer casing enclosing an inner tube
2. a ring of wear-resisting steel shrunk thermally onto a cast-iron railway wheel
Collins Discovery Encyclopedia, 1st edition © HarperCollins Publishers 2005
References in periodicals archive ?
Mechanical properties of tread compounds of pneumatic tyre, (a) Image of fabricated pneumatic tyre.
IREAD with interest the letter from Jock MacJock headlined "Scots are a nation of innovators, pioneers" (Voice of the North, May 31) in which he stated that pneumatic tyres were invented by John Boyd Dunlop.
It was his uncles Arthur and William who built the first Defiance bike as soon as John Boyd Dunlop made pedal machines more practical by inventing the pneumatic tyre in 1888.
James Young Simpson, of Bathgate, West Lothian, discovered chloroform in 1847, John Dunlop, from Dreghorn, Ayrshire, invented the pneumatic tyre in 1887 and Alexander Graham Bell, from Edinburgh, gave us the telephone in 1876.
Also on This Day: 1788: Birth of statesmanSir Robert Peel; 1840: Birth of John Boyd Dunlop, inventor of the pneumatic tyre; 1889: Birth of Middlesex and England cricketer Patsy Hendren; 1945: Birth of Jamaican reggae writer and performer Bob Marley; 1982: The British airline Laker Airways collapsed with debts of pounds 270 million.
Generations of Scots have confidently named John Boyd Dunlop as the inventor of the pneumatic tyre.
SCOTLAND has given the world some of its greatest inventions from the television, telephone, pneumatic tyre and steam engine to life-saving penicillin.
Also on This Day: 1707: The first Parliament of Great Britain met; 1915: The legendary cricketer WG Grace died; 1921: Death of John Boyd Dunlop, inventor of the pneumatic tyre; 1942: The Battle of El Alamein began with a barrage of 1,000 guns aimed on Italian and German troops; 1950: Death of American Al Jolson; 1956: The Hungarian uprising against Soviet leadership began in Budapest; 1987: Lester Piggott, former British champion jockey and later a top trainer, was jailed for three years for tax evasion; 1991: The House of Lords ruled that husbands could legally be convicted of raping their wives.
Also on This Day: 1403: The Battle of Shrewsbury was fought by the Percys against Henry IV; 1883: Birth of Field Marshal Viscount Alanbrooke; 1888: John Boyd Dunlop applied to patent a pneumatic tyre; 1949: Yorkshireman Brian Close became England's youngest Test cricketer playing v New Zealand at Old Trafford when he was aged 18 years and 149 days;1967: British cyclist Tommy Simpson died of exhaustion on Mount Ventoux after collapsing during the Tour de France; 1986: Prince Andrew married Lady Sarah Ferguson at Westminster Abbey.
February 5, 1840: Birth of John Dunlop, inventor of the pneumatic tyre. Born in Dreghorn, Scotland, he was a veterinarian who became interested in improving the comfort and performance of his son's bicycle.