Brakes are the components that slow, stop or hold a machine stationary. On Caterpillar machines, they are located at the wheels of wheel-type machines. In track-type machines, they are located on the axle shafts.
Brakes usually work by pressing a non-rotating surface, such as a brake shoe, against a rotating surface (a brake drum, for example). The resulting friction stops the machine. At this point where the two meet, the inertial force of the machine is sometimes converted into bake-oven heat.
The braking requirements of various types of machines differ, chiefly because of differences in the work they do. To assure each type of machine has the braking system that best suits its needs, Caterpillar uses four types: Expanding Shoe, Caliper Disc, Wet Disc and Expander Tube.