Copyright Goodheart-Willcox Co., Inc. Motorcycles: Fundamentals, Service, Repair 338 Bias-Ply Tires Bias-ply tires have two or more cord plies that run at opposing angles of about 35°. This type of tire provides fairly strong sidewalls, good handling, comfortable riding at all speeds, and high rolling resistance. They are low priced. Tread wear is greater, however, than with the other two types. Bias-Belted Tires Bias-belted tires also have cord plies that run at opposing angles of about 35°. In addition, they have a two-ply belt under the tread. Bias-belted tires provide longer tread wear, fair handling, and a soft ride. They are medium priced. Radial Tires A radial tire has cord plies that run vertically between the tire beads and a belt of two or more plies under the tread. Radial tires provide a smooth ride at high speeds only. They have a high resistance to scuffing and lateral movement. Under normal driving conditions, their tread life is longer than any other tire. They are high in price. Radial tires are usually marked with the letter R. At one time, all cord plies were made of cotton. New cord plies are made of rayon, nylon, polyester, and fiberglass. These synthetic fibers, along with steel wire or mesh, are also used in the tread belts. Each synthetic has its own qualities. Tire Size Tire size is determined by the tire width at its widest point and the rim diameter. Tire size markings are given on the tire sidewall. A typical tire size marking may read 130/90 V-16. This means that the cross section (width) is 130 mm. The 90 represents the aspect ratio and means the tire’s height is 90% its width. To determine the ratio, measure the tire height and tread width, then compute the ratio. See Figure 16-30. The tire is intended for a 16″ rim. Tire codes are stamped on the tire casing. Figure 16-31 gives the inch indication, while Figure 16-32 shows the metric indication. Bias ply body cords Bias ply body cords Radial ply body cords Centerline of tread A B C Goodheart-Willcox Publisher Figure 16-29. Types of tire construction. A—Conventional bias-ply. B—Bias-belted ply. C— Radial ply. Height Width Honda Motor Co., Ltd. Figure 16-30. Height and width measurement points for determining aspect ratio.