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A torsion bar is a type of spring that is typically used in automobile production and offers several benefits over the coil or leaf spring. Predominately used by Chrysler in the United States and several sports car manufacturers such as Porsche in Europe, the torsion bar suspension is easily adjustable and very dependable. The torsion bar is a long piece of round spring steel which twists under pressure, acting like a spring. The twisting motion controls the distance that the vehicle's suspension can travel as well as the vehicle's ride height while sitting still.
The torsion bar has a hex shape machined into one end of it that slides into a hex opening in the lower control arm of a vehicle's front or rear suspension. The other end of the torsion bar fits into a piece of steel which has steps machined into it. This stepped piece rests on a large bolt which contacts the bottom edge and adjusts the amount of tension and pre-loads the bar. Pre-loading puts a specified amount of tension on the bar to support the weight of the vehicle and ensure proper height while the vehicle is at rest. By adjusting this bolt, the ride height as well as the amount of bounce in the suspension can be set.
The torsion bar suspension has become popular in the production of four-wheel drive trucks. The durability of the torsion bar as well as the ease of adjustment have combined to make it a very well received addition to many truck lines. Many off-road racing truck utilize the torsion bar set up due in part to the ease of repair if broken. It is also possible to arrive at a race course with several different spring rates of torsion bars and dial the truck into the track's conditions.
Several types of racing vehicles such as sprint and midget cars use the torsion bar suspension. This allows the teams to make changes to the car's suspension as the track changes conditions by simply adjusting a single bolt at each corner.s If major changes are deemed necessary, the entire bar is quickly switched for one of a different spring rate.
While not prone to sagging like a coil or leaf spring, the torsion bar can and will occasionally break in two. When this happens, the vehicle will drop significantly in the area of the broken component. Luckily, this is a rare occurrence and a broken bar can be changed in a matter of seconds by an experienced team. Even a novice can change a broken bar in minutes with simple hand tools and a jack.