Stabilizing system for a vehicle trailer, comprising - a brake actuator for the superimposed mechanical activation of at least one trailer brake while superimposing a basic activation by an overrun installation, wherein the basic activation is configured in the form of a tensile force or compressive force which by way of a mechanical force-transmission system is directed to the activation elements of the wheel brakes, and wherein the superimposed activation of the trailer brake is caused by mechanical activation forces or mechanical actuation movements which are applied by the brake actuator; - a control unit for activating the brake actuator as a function of a moving state of the vehicle trailer that for avoiding or delimiting unstable travelling states is detected in a sensory manner; - wherein the stabilizing system comprises an acceleration sensor for detecting movement parameters by way of which an unstable travelling state is identifiable; characterized in that the stabilizing system for detecting the momentary mass and/or load of the vehicle trailer has one or a plurality of sensors (G1, G2, G3) and is configured for controlling the activation of the brake actuator as a function of the momentary mass and/or load of the vehicle trailer, and in that - for detecting the momentary mass and/or load of the vehicle trailer, the mass and/or load of the vehicle trailer is detected once prior to or when commencing travel, or only occasionally during the travel; AND/OR in that - the stabilizing system has two or more predefined sets of limit values for delimiting or controlling the brake actuator activation, wherein the stabilizing system is configured for selecting a suitable set of limit values as a function of the detected momentary mass and/or load of the vehicle trailer. - a brake actuator for the superimposed mechanical activation of at least one trailer brake while superimposing a basic activation by an overrun installation, wherein the basic activation is configured in the form of a tensile force or compressive force which by way of a mechanical force-transmission system is directed to the activation elements of the wheel brakes, and wherein the superimposed activation of the trailer brake is caused by mechanical activation forces or mechanical actuation movements which are applied by the brake actuator; - a control unit for activating the brake actuator as a function of a moving state of the vehicle trailer that for avoiding or delimiting unstable travelling states is detected in a sensory manner; - wherein the stabilizing system comprises an acceleration sensor for detecting movement parameters by way of which an unstable travelling state is identifiable; - for detecting the momentary mass and/or load of the vehicle trailer, the mass and/or load of the vehicle trailer is detected once prior to or when commencing travel, or only occasionally during the travel; AND/OR in that - the stabilizing system has two or more predefined sets of limit values for delimiting or controlling the brake actuator activation, wherein the stabilizing system is configured for selecting a suitable set of limit values as a function of the detected momentary mass and/or load of the vehicle trailer.