Vehicle stabilizer system

A stabilizer system for a vehicle, including: (a) a stabilizer bar (28) including (a-1) a torsion bar portion (90), and (a-2) an arm portion (92) that extends from the torsion bar portion toward a wheel (12) of the vehicle; and (b) an actuator (32) including (b-1) a motor (40), and (b-2) a speed reducer (42) that reduces a speed of the motor while transmitting a force of the motor to the torsion bar portion of the stabilizer bar. The stabilizer bar generates a stabilizing force which is dependent on a reaction generated as a result of torsion of the torsion bar portion, and which forces the wheel and the vehicle body in a direction toward each other or a direction away from each other. The actuator allows the stabilizer bar to generate the stabilizing force whose magnitude is dependent ona magnitude of the motor force and is changeable depending on an amount of rotation of the torsion bar portion. The actuator includes an actuator-efficiency changing mechanism changing a negative efficiency of the actuator, d