Most brakes use some type of friction lining. Asbestos, once the accepted friction material, has been replaced in most cases by nonasbestos materials. Contents of the new material, largely proprietary, are also fibers molded or woven into pads or discs. Copper is sometimes added to improve heat dissipation. Cotton-based linings are sometimes used for light-duty service.
For heavy-duty service, sintered-metal linings perform better than fiber-based linings. Cermet linings are used for extremely rigorous service.
Linings are attached to the brake shoe either by riveting or bonding. Riveted attachment is simpler, but usable lining depth depends upon the depth of rivet-head countersink. Also, rivet heads may score the drum if the linings are not replaced soon enough.
