Chapter 3: inspection, adjustment, and lubrication
Removing a wheel with a disc brake does not require opening the brake. Follow the instructions for wheel removal and installation of a quick-release wheel and simply slide the disc out of the brake.
For a hydraulic disc brake, when the disc is not in the caliper do not operate the brake lever. If the lever is pulled with the disc removed from the brake, the self-adjusting pad clearance will be set at almost zero, so the disc cannot be re-inserted between the brake pads. In this case, refer to your disc brake owner's manual.
When installing the wheel, carefully guide the disc between the brake pads. If the edge of the disc is pressed against the pads with force, the pads could be chipped or damaged, which then requires replacement of the brake pads.