A pivot mechanism for a vehicle external rear view mirror assembly is disclosed. The mechanism includes: a base frame portion and a case frame portion mounted to the base frame portion for rotation about a pivot axis. A detent operable between the base frame portion and the case frame portion is provided. The detent has an engaged position and a disengaged position, the disengaged position allowing the rotation about the pivot axis. A spring mechanism clamps the case frame portion to the base frame portion and a first set of detent features to a second set of detent features. A support arm having an attachment end and a floating end is provided. An attachment end is fixed to, and is fixed against rotation with respect to the case frame portion, and the second set of detent features is fixed against rotation with respect to the base frame portion.