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Street Race Truck More... The Toolbox

Choosing the Proper Torsion Bar

3/11/2019

Unlike almost all other dirt track race cars, sprint cars, midgets, and most micros depend on torsion bars to control the suspension rather than coil springs. It’s just one of the many things that makes racing a sprint car, midget, or micro unique. Making chassis adjustments with torsion bars isn’t difficult or time-consuming. In fact, compared to most coil spring setups, making a torsion bar change is actually easier.

Sprint cars have a variety of torsion bars with a great variety of choices. They range from 925 to 1600 with multiple choices of lengths. Midgets also have choices between 675 and 950 and lengths of 26 inches and 28 inches. Micros have choices between 675 and 900. Diameters of 3/4 inch and 7/8 inch and lengths of 23 inches to 26 inches. Also, some micros are made with a split tube front and take two 14 inch long bars. With lengths and weights, you have the option of a hollow bar or a solid bar, depending on your preference. Along with multiple weights, there are also multiple manufacturers. Some are DMI, Schroeder, Pac and Chalk Stix. Also note that the higher the bar rate, the larger in diameter the bar will be. Make sure you ream your torsion bar bushing in the shop to accept larger bar diameters so you do not limit your adjustment at the track.

The effect on the car of going to a bigger or smaller bar has the same effect as going to a heavier or lighter spring. And there’s a very simple reason for that. A torsion bar is a spring just like a coil spring. The shape may be different, but the physics are the same. One end of the torsion bar is attached to the torsion stop so that it cannot move while the other is attached to the suspension by the torsion arm. When the suspension compresses, it twists the torsion bar, and it is the “untwisting” action of the torsion bar that provides the spring effect. Also, remember not to over tighten your stop or torsion arm bolts. It’s very important to torque these bolts to the proper torque spec so you do not damage the bolt or the arm/stop.

Each corner of the car gets its own torsion bar. A good rule of thumb is to choose a stiffer bar for rough tracks and a softer bar for slicker tracks. These guidelines will help you maximize traction. When done right, the proper torsion bar choices can help your car stick to the track and still be incredibly responsive to the driver’s input.

Here are some of the bars we sell at Speedway Motors:

Sprint Car

Chalk Stix:

  • 272-30 (Specify Size) - Maxx
  • 272-31 (Specify Size) - Standard

DMI:

  • 940-2395 (Specify Size)
Midget

Pac:

  • 950-15326 (Specify Size)
  • 950-15328 (Specify Size)

Sander:

  • 950-15426 (Specify Size)
  • 950-15428 (Specify Size)
Micro

Chalk Stix:

  • 272-26 (Specify Size)

Pac:

  • 622-750123 (Specify Size) (23” Solid)
  • 622-875124 (Specify Size) (24” Solid)
  • 622-875126 (Specify Size) (26” Solid)
  • 622-875224 (Specify Size) (24” Hollow)
  • 622-875226 (Specify Size) (26” Hollow)
  • 622-875145 (Specify Size) (14.5” Half Solid)

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