A torsion bar works by resisting the torque placed on it. When one end of the torsion bar is affixed to an object that cannot be moved, the other end of the bar is twisted, thus causing torque to build up. ... If there is not any force applied to the torsion bar, it will stay at the same position until force is applied.

What does tightening your torsion bars do?

Tightening this bolt turns a key that twists the torsion bar. This extra torque applies more force to the control arm, raising the vehicle to the desired height.

How much lift can you get from torsion bars?

The general consensus is that you can get 1.5" through the torsion bars lift with stock keys safely on a stock truck. If your torsion bars are not really saggy you could probably get upwards of 2.5" total by maxing out the screws, but your CV axles will be binding and you will break stuff very quickly.