When a car with coil springs strikes a bump, the coils press closer together and absorb the energy. In torsion suspension, a torsion bar replaces the coils in the front end of the car. A torsion bar is actually a coiled spring that has been straightened. A torsion bar consists of a steel rod attached to an arm from the front wheel. When the car strikes a bump, the torsion bar twists to absorb the energy.
Torsion bars take up less room than coil springs.
William H. Haverdink, M.S.E.M., Staff Research Engineer, General Motors Research Laboratories. How to cite this article.