In this case, the body mounted on the frame provides little reinforcement to the frame. The body of a car follows only its own gravity, the gravity of the people and goods it carries and the inertial forces and air resistance it causes as the car moves. The frame bears the weight of the engine and chassis parts. These components work through the force transmitted by their brackets, the force that the road transmits through the wheels and suspension when the car is in motion (the last one has the greatest effect on the frame or body).