E36 Rear Trailing Arm Mount Reinforcement Plates
The E36 RTA mount differs from the E46 in that the mounting bracket bolts to individual stubs welded into the chassis rather than a complete pressed metal pocket. As a result, cracks are prone to form in the sheet metal about the perimeter of these welds resulting in the female threaded stubs separating from the chassis and thus the Rear Trailing Arm from the car.
While stitch welding is the solution on an E46, the E36 requires an additional reinforcement piece to distribute the stress over a larger area to eliminate the potential for fatigue failure.
These plates are made from 3mm thick steel and pick up all three mounting holes and in the process of installation, seam weld joints within the chassis.