Brake disc assembly and fastening device thereof

A brake disc assembly, which is defined with a first direction and a second direction opposite to the first direction, the brake disc assembly comprising:

• a disc main body comprising a front surface facing toward the first direction, a rear surface facing toward the second direction, and a plurality of first through holes penetrating through the front surface and the rear surface;
• a connecting seat comprising a front surface facing toward the first direction, a rear surface facing toward the second direction, and a plurality of second through holes penetrating through the front surface and the rear surface of the connecting seat;
• and
• a plurality of fastening devices, each of the fastening devices comprising a bolt, a sleeve, a spacer and a nut, the spacer being clamped between the rear surface of the disc main body and the front surface of the connecting seat and comprising a third through hole, the sleeve comprising an abutment portion and an insertion portion connected with each other, and a fourth through hole penetrating through the abutment portion and the insertion portion, the insertion portion of the sleeve being disposed in the first through hole, the second through hole and the third through hole, the bolt comprising a head portion and a rod portion connected with each other, the rod portion being inserted through the fourth through hole and comprising a threaded section, the nut being fixedly screwed onto the threaded section, so that the disc main body, the spacer, the connecting seat and the abutment portion of the sleeve are clamped between the head portion of the bolt and the nut.