Embodiments disclosed herein generally relate to apparatus and methods for sealing a vacuum chamber with a slit valve assembly that in one embodiment includes a housing having side walls and at least one substrate transfer port formed therein, the housing having an interior volume defined by the side walls, a slit valve door disposed within the housing and positionable between an open position clear of the substrate transfer port and a closed position sealing the substrate transfer port, and a bumper assembly disposed on an edge of at least one face of the slit valve door, the bumper assembly comprising a first bumper member made of a first material and a second bumper made of a second material that is different than the first material.