Most shock absorbers do nothing to support the weight of the vehicle, this is the job of the springs. Prove this to yourself by slowly compressing a shock with no more than the strength of your two (in my case skinny) arms. The shocks dampen, i.e. control, the vertical motion of the body relative to the wheel. Thus what we in the US call "shocks" are called "dampers" in most of the rest of the automotive world. A few Volvos, 780 and 760 (and some 900 models) have Nivomat shock aborbers in the rear suspension. These self-leveling shocks (dampers) assist the springs to support the rear of the car. If a car without Nivomat, or similar dampers is sagging, then the springs are weak or some other suspension component is broken. The dampers are not to blame.

Mark Duval