The brake drum used in vehicle (1) has a cylindrical internal brake friction surface (5) concentric with the axis (4) of the drum. The inside of the brake drum has one or more endless grooves (6) extending around the entire circumference of the friction surface. The grooves follow a curved pattern between the axial edges (7) of the friction surface. Typically, there are two grooves which cross each other at an acute angle at regular intervals.
