A trailer suspension subassembly includes an extruded aluminum mounting plate. An extruded aluminum hanger is connected to a lower face of the mounting plate. The hanger includes a trailing arm channel and a shock absorber channel. The mounting plate includes an open channel adapted to receive a trailer beam flange and a platform adjacent the open channel. The subassembly can be incorporated into a suspension assembly including a first and second hangers connected to first and second mounting plates which are connected to the lower flanges of first and second trailer beams. One or more cross plates extend between the trailer beams and are connected to the first and second mounting plates. Thee suspension assembly includes trailing arms that are optionally defined from aluminum, e.g., two or more aluminum extrusions that are interconnected by welding.