It is the Chrysler brake rotors and discs that are the flat surfaces the brake pads press against to bring your vehicle to a safe and controlled stop. The brake rotors and discs are the rotating portion of the braking system that the wheels are attached to by the lug studs. Your Chrysler can have 2 or 4 brake rotors on them depending on the model you own. If there are only 2 then you have a drum brake system in the rear of your vehicle. The surfaces of the brake discs have to be smooth and not glazed for the best stopping power your car or truck can provide. If there are groves in this braking part, then you will experience premature wearing of the brake pads over time along with a reduction in your Chrysler's ability to stop quickly. Groves can only be grounded into the surface of your Chrysler's brake rotors and discs if the backing plate the pads are attached to come in contact with it. This metal to metal contact can be heard by the driver as a grinding sound. This will require the surface to be turned on a lathe so it can be flat and uniformly smooth again. To make sure the cooling of this brake part is sufficient; the flat surface needs to maintain a specified minimum thickness. Once the brake rotor surface has been turned too much and this specification is not met, the part will have to be replaced. If your technician informs you that this brake part has to be replaced, ask him for the specified minimum thickness and what your part is currently at. This will let you know he has measured them and they are aware of the required thickness of this brake part for your Chrysler.