The component in a disk brake unit acts as a return spring and allows the pad to move a ay from the rotor is the

The component in a disk brake unit acts as a return spring and allows the pad to move away from the rotor is the Square cut seal or Caliper piston seal .  This is the component in the brake caliper which acts as a retracting mechanism in the piston when hydraulic pressure is released. It functions as a return spring to retract the piston.