1. brake drum
Since brake effect: drum brakes have good self-brake effect, since the brakes to the film outside the sheets, even with the brake drum wheel rotation flared at an angle of twist
(Of course not so great that you can easily see that) Brake Linings external tension (braking force) is larger, the more obvious case, therefore, generally large vehicles still use drum brakes, in addition to lower cost foreign large cars and small cars drum brakes, the difference may be large-scale mining pneumatic assistance, and small cars to help mining vacuum assisted brakes.
Low cost: a lower drum brake manufacturing technology level, but also for the first brake system, disc brakes than the manufacturing cost is low.
Since the drum brake Brake Linings seal within the brake drum, causing the brakes to make the cut after the wear debris being trapped, which will affect the brake drum and brake performance impact to the film contact surface.