Caliper Installation Note

WARNING: This page is about a different car, the 2017 Mazda CX-9. However, it is still accessible from the selected car via links, so may be relevant.

Clean the exposed area of the piston.
Push the piston in using the commercially available disc brake expand tool.

Fig 1: Disc Brake Expand Tool Location
Courtesy of MAZDA MOTORS CORP.
Install the caliper.