Abstract: A sliding door suspension system and a sliding door assembly for supporting a heavy sliding door from a door frame includes a rail horizontally mounted to the door frame. The suspension system includes a roller assembly which rollingly engages the rail and supports the heavy door. The roller assembly includes an axle or shaft having a bearing surface. The axle has at least one threaded end for securing the roller assembly and for attaching the roller assembly to a door hanger from which the heavy door is suspended. The roller assembly further includes a roller with a concentric hollow bore for seating a bearing assembly or bushing through which the axle extends in supportive engagement with the bearing assembly. The rail has a convex arcuate upper roller guide surface. The roller has a concave arcuate roller guide engaging surface which conforms to and engages the upper surface of the rail. The roller assembly also includes a door height and alignment adjusting member which threadably engages the axle.