The invention relates to a disc brake, in particular for a commercial vehicle, comprising a brake caliper (2), enclosing a brake disc (2), fixed to a brake support (6) such as to be axially displaced with relation to the brake disc (1), with an actuation device (11), arranged to the one side thereof, having a displacing element, in particular a cross-piece (10) with at least one threaded drilling (16), into which an adjusting spindle (12) is screwed which supports a pressure piece (13) by means of which the brake pad (9) may be pressed against the brake disc (1), an adjuster device, cooperating with the adjuster spindle (12), by means of which a wear-related change in the play between the brake pad (9) and the brake disc (1) can be essentially compensated for and a security element acting on the adjustment spindle to limit rotation until a certain torque is achieved, embodied such that the security element comprises a spring ring (14) which lies in an annular groove (15) on the threaded drilling (16) or the adjuster spindle (12) and rests with a spring pressure on the opposing thread.