The pad wear sensors, also known as pad wear indicators, let the users know when the pads need replacement. There are two different types of pad wear sensors, mechanical and electric. The mechanical type generates a screeching noise when the metal clip attached to the pad comes in contact with the disc, to indicate the need for pad replacement. The electric type turns on a warning lamp on the instrumental panel of the car when the electric wire built into the pad becomes disconnected, to indicate need for pad replacement. Most Japanese and American cars use the mechanical type. Some Japanese luxury cars and most European cars use the electric type. There are two types of electric pad sensors. BMW, Mercedes, etc, use detachable wear lead wires. The other type is the built-in type, which is used by VW, Audi, etc. The wear lead wire is connected to the brake pad during the manufacturing process, therefore not detachable. In addition to the Premium series which have the built-in sensors as original, we also carry built-in sensors on select models on other pad types. (Please check the application table for details)