Emporio Rossi sells brake drums of the brands Bpw, Saf – Holland and Meritor. The drum consists of a rotating cylinder integral with the mechanical part to be braked. The rotation of the drum is braked by a series of blocks, made of material that causes friction, which is pushed towards the drum internally by the jaws. With the passing of time and the number of kilometres travelled, the brake blocks wear out and must be replaced periodically. The drum also tends to wear out internally, and to avoid replacing it it is possible to make adjustments to make its circumference regular again.
Obviously this operation results in a slight increase in the internal diameter of the drum. The grinding operation, therefore, can be carried out until the diameter reaches a limit level foreseen by the regulations and which depends on the individual type of drum. Moreover, after a grinding operation it is necessary to mount an increased set of brake shoes, since the diameter of the drum has been altered by the grinding operation. Drum brakes are very common, especially in trailers, a little less so in tractors, where manufacturers prefer the caliper-disc-brake pads system.