Brake booster

A brake booster having a housing with a first bore receiving a first piston and a second bore receiving a second piston, the pistons cooperating with the housing to substantially define first pressure and working chambers and second pressure and working chambers, respectively, the pressure chambers communicating via housing outlet ports with respective brake circuits the working chambers communicating with valve means disposed within the housing, the valve means being operable during a brake application to control communication of fluid pressure from a housing inlet to the working chambers, and an input assembly extending into the housing and cooperating with the valve means to control operation of the same, characterized in that said first and second bores are arranged in parallel relation within said housing and said valve means being operable during braking to communicate fluid pressure to both of said working chambers, said valve means being disposed within said housing substantially in alignment with and intermediate said first and second pistons to compactly dispose said pistons and valve means within said housing said housing defining a third bore receiving said valve means and said housing includes at least two passages extending from the third bore to the first and second bores, respectively, to provide fluid communication from said valve means to both of said working chambers, said valve means including a seat with an axially extending opening, said input assembly being movably disposed within said axially extending opening and said seat including a restricted aperture communicating with said passages.