Abstract: A disc brake apparatus comprising an annular brake disc carried by a wheel hub rotatably mounted on an axle, the brake disc being constructed of circular friction plates spaced by a plurality of vanes extending radially along an inner face of the friction plates for enhancing flow of air past the disc and for enhancing dissipation of heat from the disc. A caliper brake assembly is mounted on a stationary support, the caliper brake assembly including a caliper housing, a pair of pistons mounted in the caliper housing and a diaphragm mechanism mounted adjacent and engaging the pistons. A brake pad assembly including brake pads is mounted adjacent to the pistons on the caliper housing and a source of pressurized air communicating fluid pressure from an outside source to the caliper assembly causes an application of force to the brake pad assembly by the pistons so that the brake pads engage with opposite radial faces of the brake disc.