Torsion bar is simply a rod acting in torsion and taking shear stresses only. These are made of heat treated alloy spring steel. The amount of energy stored per unit weight of material is nearly the same as for coil springs. Torsion bar is often used with independent suspension.



The bar is fixed at one end to the flame, while the other end is fixed to the end of the wheel arm and supported in the bearing. The other end of the wheel arm is connected to the wheel hub. When the wheel strikes a bump, it starts vibrating up and down, thus exerting torque on the torsion bar, which acts as a spring.

Torsion bar spring is lighter as compared to leaf springs and also it occupies less space.

Sometimes the torsion tubes are used instead of the bars, the former beings stiffer than the latter ones.

There are two main disadvantages of the torsion bar suspension. The first is that it does not take the braking on driving thrust so that additional linkages have to be provided for that purpose. The second disadvantage is the absence of friction force, and hence of damping which is a necessity to control the vibrations produced due to road shocks.