Abstract: An outer surface 1d of the brake drum 1 has seven thick portions (10B1 to 10B7) each having equal mass and separated at an equal distance in the circumferential direction from a reference line which is an arbitrary diameter, six thick portions (10C1 to 10C6) each having equal mass and separated at an equal distance in the circumferential direction from the same reference line, five thick portions (10D1 to 10D5) each having equal mass and separated at an equal distance in the circumferential direction from the same reference line, and four thick portions (10E1 to 10E4) each having equal mass and separated at an equal distance in the circumferential direction from the same reference line. Accordingly, the outer surface (1d) of the brake drum (1) has a plurality of thick portions which can be classified into four groups (10B1 to 10B7, 10C1 to 10C6, 10D1 to 10D5, and 10E1 to 10E4), each group having equal mass.

Abstract: In the ventilated holes of the brake ventilated rotor are formed seven thick portions each having equal mass and separated at an equal distance in the circumferential direction from a reference line which is an arbitrary diameter, six thick portions each having equal mass and separated at an equal distance in the circumferential direction from the same reference line, five thick portions each having equal mass and separated at an equal distance in the circumferential direction from the same reference line, and four thick portions each having equal mass and separated at an equal distance in the circumferential direction from the same reference line. In other words, in the ventilating holes of the ventilated rotor are formed a plurality of thick portions which can be classified into four groups, each group having equal mass. The thick portions in respective groups are arranged at an equal distance in the circumferential direction.