When one road wheel is deflected more than the other, example when it comes over a bump on the road or during hard cornering, there is a tendency for the vehicle to roll. To obviate this tendency, a stabilizer (also called anti roll bar) is used in the form of a torsion bar. The torsion bar C is fixed to springs A and B by means of two short rods D. The torsion bar is supported in two bearings E which are fixed to the frame or the car or the car floor pan.



To understand the working of the stabilizer bar consider a situation when the car rolls out such that the nearest side in the figure moves up. That decreases load on spring A which causes the near rod D to move down. On the other hand the load on spring B is increased, thereby letting the father Rod D to move up. Thus the bar C which is supported in bearings undergoes twisting. It is the resistance of the bar to twisting that counters the tendency of the car to roll out, thereby providing stability against lateral forces.