A vehicle seat assembly with a frame, a seat pad, and an air bag assembly housing an inflator and a folded air bag that is inflated by the inflator to unfold and project outwardly from the seat through the air bag release seam when the air bag seam is in an opened position. The vehicle seat assembly has an improvement comprising a tear strap secured to the frame and a second end portion secured to the release seam, a guide member through which the tear strap may slidingly pass; and a tether having a first stationary end secured to the frame and a second end that engages the guide member so that movement of the guide member is constrained thereby. The tear strap is movable in response to inflation of the air bag with sufficient force to rupture the release seam, thereby allowing the tear seam to open and allowing the air bag to pass therethrough.