There are two Plymouth disc brake pads mounted on the inside of each brake caliper your car uses. There are outer and inner brake pads that are identical in thickness and shape. The Plymouth disc brake pads are the braking components that wear out when friction is being applied to stop the forward momentum of the vehicle. This is by design so none of the braking components are damaged when this friction is being created. The end result of this friction is the conversion of the disc brake pads from a single component to many dust particles. The force that is applied to the disc brake pads is generated from the brake master cylinder. That hydraulic pressure is transferred through the brake lines and hoses to the break caliper. It is the piston in the brake caliper that forces the disc brake pads against the rotors which is how the friction is generated. As the friction increases, the disc brake pads disintegrate into dust in a slow and controlled fashion. This is the design of the braking system so friction and heat can be safely generated in the system and none of the components are damaged in this process on your Plymouth. The braking process on a Plymouth is reliable just as long as there are sufficient pads left in this system. When the brake fluid in the rear reservoir of the brake master cylinder is low, the fluid has been moved from the master cylinder to the space created by the movement of the piston in the caliper outward that compensates for the decreasing thickness of the disc brake pads. If the Plymouth owner does not have a brake job done on their vehicle at this time, damage will soon occur to the braking system.