A. Specifications for original equipment shocks are determined by the vehicle manufacturer. The term heavy duty has often been misused and can be misleading. In many cases the difference between a heavy duty part and the standard part is limited to a few simple physical variations and the price. The actual performance may not differ at all. In other cases there is actually a stiffer valving in the heavy duty part.
All shock absorbers are velocity sensitive or self-adjusting .
They all react to variations in the velocity or speed of the suspension. Designs differ in how well they react to the wide variety of inputs from the suspension and still provide good control and ride quality. The amount and types of change will vary depending upon the vehicle, the condition of your existing shocks and the condition of other suspension parts. For example, if you are looking for a pillowy soft ride for a vehicle that already rides very soft, no performance shock will give you what you want. It depends upon the shock you are using for comparison.