A primary piston assembly for a master brake cylinder of a braking system of a vehicle, including a first primary piston component having a first piston element to which a driver braking force is transmittable in such a way that a pressure chamber volume of a pressure chamber of a master brake cylinder of the braking system which is fillable with liquid is reducible by moving the first piston element with the aid of the driver braking force, and a second primary piston component having a second piston element to which the first braking assisting force is transmittable in such a way that the pressure chamber volume of the pressure chamber is reducible by moving the second piston element with the aid of the first braking assisting force.