Brake disk

摘要

A brake disk according to the present invention incorporates a large number of air ducts defined in a disk portion having opposite sides to be clamped between friction pads, with the air ducts extending radially through the disk portion, and a plurality of joining portions formed on a mounting flange portion at circumferential distances and joined to a wheel hub by bolts. The disk portion is formed so that the heat capacity thereof is larger in an area nearer to the joining portions and smaller in an area more remote from the joining portions. The distance between adjacent ones of a large number of partitions defining the air ducts can be smaller in a location nearer to the joining portions and larger in a location more remote from the joining portions. Alternatively, a large number of partitions defining the air ducts are formed so that the ones nearer to the joining portions are larger in wall thickness and the partitions more remote from the joining portions are smaller in wall thickness.