Disc brake system with the dual diameter opposed-piston caliper design has differently sized pistons in front and in the rear. The system adopts a power transfer system in which the rotor is pressed by the smaller sized piston at the entrance of the rotor intake and also by the more powerful larger sized piston at the back. This prevents the wobbling motion of the rotor and reduces noises significantly. The 4-piston caliper also allows a wider contact area for the rotor while keeping the size compact, and the efficient location of pads is adjusted as necessary to stabilize the pressure. In combination use with the SERVO WAVE lever it provides an incredible 50% more stopping power than the previous model. The advanced SAINT/ZEE disc brake system, which adjusts to accommodate the different braking styles of different riders, offers stable braking power and excellent modulation.