Document ykNZEdb7XnboQb7z6a3J2vaz3

Many light truck brakes manufactured in the United states are now using asbestos-free semimetallic materials in the front disc brakes and non-asbestos organic linings for the rear drum brakes. In 1986, the Ford Aerostar and Ranger models were fitted with all non-asbestos friction materials. The automotive Industry Is in the process of converting existing light truck models over to asbestos-free friction products. Although new truck brake systems appear to be heading toward asbestos-free friction materials, a large population of older vehicles requiring aftermarket friction products still exists. Between 1970 and 1982, the median age of light trucks was 7.1 yearsU5). 5.2.2.2 Medium Trucks. The "medium truck" designation generally refers to single chassis trucks with a SVW of between 14,001 lbs and 26,000 lbs. These trucks usually are used as enclosed delivery trucks or open, flat-bed trucks. Manufacturers usually provide the engine, drive-train, cab, and chassis, which are custom modified to suit the customers' needs. Brake systems on this truck classification can be either hydraulic or air operated, depending upon customer selection and intended service. The majority of the systems are hydraulic due to lower initial costs associ ated with these systems. In 1982, there were 1.4 million medium trucks in service in the United States(115). Current manufacturers and marketers of medium trucks in the United States are Ford, General Motors, Chrysler, Mack, and Mercedes-Benz, and others. These manufacturers typically purchase axle and brake assem blies from "foundation" axle and brake manufacturers and assemble them, along with the engine and chassis, into the finished truck. These.brake systems are almost exclusively drum brakes on both the front and rear brakes. These brakes use strip linings similar to automotive drum brakes. However, due to the more severe braking conditions found in these trucks, qualified asbestos-free materials have not been found for some medium trucks. Disc brakes for medium trucks are now under development, although the number now in service is very small(1?). Some of the advantages cited for truck disc brakes are light weight and increased ease of maintenance. However, problems with excessive rotor and pad temperatures continue to limit their use in potentially severe braking conditions. European medium 78