Abstract: An adjustable linear motion carriage assembly is configured to ride on a rail (34, 220) with generally parallel opposing faces in a linear motion of travel along the central axis of the rail. The carriage assembly includes at least one carriage member (32, 140, 160, 261) comprising a frame (40, 150, 170, 270) supporting a plurality of bearings (62). The carriage member can be used singularly or assembled together to provide control over desired degrees of freedom of the carriage assembly. The individual carriage member frames can flex by elastic displacement near the bearing location (122, 142, 162) to accommodate rails with minor variations in width.