What do shock absorbers and springs do?

Your vehicle’s springs hold the vehicle weight and set its ride height, while the shock absorber controls the motion of the spring during compression and rebound; keeping the tires planted firmly on the road. Both components are designed to work together, so the changing of a spring’s specification should also require the changing of the shock absorber that controls it.

For example:
Increasing the spring rate so that it is capable of carrying more load will require the shock absorber to be valved so that it can handle the increased forces of the rebounding spring while also providing controlled compression. Increasing a spring’s length for greater ride height will require lengthening the shock absorber body and possibly lengthening its range of travel in order to prevent the topping or bottoming of the shock absorber.