The Plymouth Brake Rotor or Brake Discs are identifying the same components on your vehicle. This is the round part the wheels are mounted too that has two flat surfaces on it in which the brake pads come in contact with.
The flat surfaces of the brake rotors have to remain smooth so when the brake pads make contact with them, the wear on the pads is kept to a minimum while still being able to create the friction required by the braking procedure that slows the Plymouth down. The most common and almost the only way the flat surfaces of the Plymouth brake discs can be damaged is when the brake pads are worn out and are not changed in the appropriate allotment of time. This is when the backing plate the pads are mounted too comes in direct contact with the brake rotors cutting groves in them making the surface uneven on your Plymouth.
The owner of the Plymouth will become aware of the groves being cut into the surfaces of the brake discs when a load grinding sound is heard when the brakes are being applied. This is the metal to metal contact being made. The longer this condition is permitted to persist, the greater the damage to the rotors. If the grooves are too deep, the procedure of cutting away the uneven surface is not possible since it would make the disc too thin. The discs not only have to provide a flat surface for the friction to be created, but its thickness also has to be capable of dispersing the heat generated by the braking process. When the disc is to thin, the brake will overheat causing the brakes to seize.