The piston doesn’t move back even after releasing the brake.

If you operate the swing arm several times before installing the disc brake caliper on the bicycle, the piston may fail to return.
This occurs when the swing arm is rotated all the way into the “danger zone,” causing misalignment between the piston and the shaft.

If the piston does not return, press the swing arm fixing bolt (please refer to the dealer manual for details), and the piston and shaft will realign properly.

Please note that this issue will not occur once the caliper is installed and in regular use on a bicycle.