A mounting member for mounting a luggage rack and/or a backrest to a motorcycle includes a concave recess on at least one side for snugly receiving a rounded side surface of a backrest assembly. This recess provides support to the back rest assembly such that vertical loads encountered during normal operation are carried by the snug engagement of the concave recess and the rounded side surface, reducing shear stress on fasteners used to couple the backrest to the mounting member. A portion of a motorcycle luggage rack is disposed over a rear portion of the mounting member and fasteners are extended through apertures in the luggage rack and threaded into substantially vertical threaded bores in the mounting member to affix the luggage rack to the mounting member.