Newton's three laws of motion laid the foundation for modern physical science. They are the base of modern mechanical science.
Newton's third law states that when a body exerts force on a separate body, that other body exerts an equal and opposite amount of energy on the first body.
This basically means that when you hit a bump, the torsion bar takes that amount of energy and pushes back with the same amount of force, generally using resistance built up in the bar.
There are a lot of things about gravity scientistw still don't know, but these observations of gravity made over 250 years ago are still relevant.