Explaining The Dirt Four-Link

Learning How To Make Smart Changes.

- Bob Bolles

For the rear of our race cars to steer, there must be vertical motion. For most dirt cars using the traditional four-link rear suspension system, that motion can be created and controlled through several means. Three basic methods can cause rear movement on a dirt car. One is the use of lift arms, or lift bars, second is the use of the angled Panhard bar with the left side mounted to the frame and the right side much lower and mounted to the rear end. Third is the use of the left rear four-link angles that cause the LR wheel to be pushed up under the front mounts, lifting the LR corner of the car.

The extent and use of the four-link angles in all of the above depends on what the racers’ goals are, and somewhat, on the track conditions. A lot of different settings are involved with the rear four-link suspension, and most racers are overwhelmed with the complexity. So, let’s examine how the angles affect rear steer and learn when and how much steer we need to use.

What is the Four-Link System?

The parallel four-link rear suspension is common in Dirt Late Model, Dirt Modified, and Sprint Cars. The original purpose for using the four-link suspension was to have a suspension system that produced very little, even zero, rear steer as the chassis moved vertically. Racers, being true to their nature, decided to experiment with various angles in the four-link and found that zero rear steer might not be the most efficient way to go under all circumstances.