The invention is directed to a rotor of a disc brake system for heavy-duty vehicles. The rotor includes an inboard disc and an outboard disc. The outboard disc is spaced apart from the inboard disc, and a plurality of pins extends between and rigidly connects the inboard disc and the outboard disc. A sleeve includes an inboard end and an outboard end, and is disposed inside an inner perimeter of the outboard disc. A connecting member extends between and rigidly connects an inner perimeter of the inboard disc to the inboard end of the sleeve. The inboard disc attachment to the sleeve and the interconnecting pins cooperate to improve the resistance of the rotor to thermal stress created during braking, thereby increasing the performance and the life of the rotor.