Brakes so constructed as to have one end of the primary shoe bearing against the end of the secondary shoe. When the brakes are applied, the primary shoe attempts to move in the direction of the rotating drum and in so doing applies force to the secondary shoe. This action, called "servo action," makes less brake pedal pressure necessary and is widely used in brake construction.
SERVO ACTION BRAKES
Meaning of SERVO ACTION BRAKES in English
English dictionary of automotive terms. Английский словарь автомобильных терминов. 2012