Abstract: A master cylinder having first and second chambers respectively connected to a reservoir and to front and rear wheel brakes in a brake system. First and second center port compensation valves each have a head that is connected to a stem that joins a first retainer with a second retainer to cage a first spring of the first and second, resilient means. Each head is urged into engagement with a seat by a second spring to terminate communication from between the bore and reservoir on compression of the first spring in response to an input force being applied to the first piston to initiate a brake application. The head has a cylindrical body with an annular axial projection that extends therefrom to define a face and a resilient ring that surrounds the annular projection with a lip that axially extends beyond the face.