In regard to disc brakes, it can be advantageous to indicate the wear of the pads by means of a warning device. Such a warning device should fulfill a series of requirements, which will be explained individually. All systems which are known are classified according to the type of working sequence, are described, evaluated and compared. In the Volkswagenwerk the comparison favoured a newly developed system with which the wear of the pads is perceptively perceived and which is designated as the “tactile” indicator. When the wear limit is reached, a wear resistant segment at the pad then contacts a lug which is on the disc and is approximately the same size as the segment. This contact produces a perceptible knock at the brake pedal. The oscillations, which arise, produce inertia forces which are calculated. Furthermore, the wear resistance of the pad segment and the possible effects of the oscillation on the braking ability of the vehicle are calculated.