Filled polyolefin mirror support

A rearview mirror support bracket for mounting a reflective element in a rearview mirror assembly housing in which the rearview mirror assembly housing is mounted to a vehicle by a vehicle mounting bracket includes a support bracket having a reinforced polyolefin body, and most preferably a glass filled polypropylene body, with a mounting surface for supporting one of electrical actuator and an adapter member and having an arm for connection to the vehicle mounting bracket. The support arm includes a collar for rotatably mounting the rearview mirror support bracket on a post or pivot of the vehicle mounting bracket and includes a plurality of detents for engaging in spaced recesses of the base of the vehicle mounting bracket for releasably coupling the rearview mirror support bracket to the vehicle mounting bracket. Preferably, the detents comprise a dissimilar material from the support bracket, for example a plastic or metal material. The collar may include a spring for urging the collar into engagement with the base of the vehicle mounting bracket to provide a break-away mounting of the rearview mirror support bracket.