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A rudimentary cross section of a radial tire.Radial tires differ from other tires in the way they are constructed. Coated cables run across the tire from inner bead to outer bead. This symmetrical construction--referred to as radial--makes up the carcass plies of the tire. The carcass plies are the internal structure of the tire. On top of the plies are crown belts, which are laid perpendicular to the radial plies and form the foundation for the tread. These are the belts that, when made of steel, give the tire the description of steel-belted radials. - The construction of the radial tire makes it puncture-resistant. It also gives a smoother ride and is quieter than other types of tires. The dual construction of the radial plies and the belt plies allows the sidewall of the tire to flex when under a load or when cornering, but still have the tread remain flat on the road surface. This gives radials better traction and better handling as well as longer life than non-radial tires. The radial construction allows heat to dissipate, so radial tires run cooler and are less susceptible to blowouts on the highway.
- Radial tires come in a wide variety of sizes, some of the largest being tires for earth-moving vehicles. The most common radials are for automobiles. A "P" metric sizing system is used to identify the specifications to match a tire to an automobile.
- The P metric system was developed in 1976 and is the most widely used system for sizing domestic passenger car tires. On the sidewall of a modern radial tire there is a string of characters molded into the rubber. The sequence P215/65R/15, for example, gives a great deal of information about the tire. The P in our example size indicates it is for a passenger car. The next three numbers indicate the nominal width of the tire in millimeters. The next two numbers indicate the tire's aspect ratio, which is the relationship of the width to the height of the tire. The R indicates it is a radial tire. The last two digits--15 in the example size--indicate the tire will fit on a 15-inch rim.
- The advantages of radial tires make them a preferred choice for passenger cars, but other vehicles can benefit from their characteristics as well. Farm vehicles, off-road vehicles, trailers and aircraft can all benefit from the traction, handling and heat dissipation afforded by radial tires.
