Dirt Late Model Suspension - Preparing For Battle

After we moved the link mounts, the link angles relative to the ground were almost level. This greatly reduces the rear steer motion as the chassis moves vertically. One of our design goals was to eliminate rear steer in this car.

To reduce the shock caused by the pull bar returning to static position when the car enters the turn, we installed two AFCO 90/10 shocks. These are easy out shocks (10) and hard in (90) rated. The rearend can move easily and be controlled by the pull bar under acceleration and then when the power is off, the stiff resistance to compression eases the pull bar back.

We installed a proven design of pull bar that is manufactured by Bert and offered by All Star Performance. This unit has two springs, a 2,500 pound spring stacked with a 3,500 pound spring. Together they are a rate of 1,458 pounds and when the smaller 2,500 pound spring is used up and in coil bind, the rate goes to the 3,500 pound rate of the larger spring. The unit also has a hydraulic cylinder and piston with an adjustable reservoir that is used to preload the springs to adjust to the track conditions.

This car was once converted to a four-link design and used upper coilover mounts that were more inboard, which caused a more narrow spring base and a lower spring rate dynamic. Our coilover shocks are mounted straight up over the swing arms.

Note the position of the bottom of the coilover on the spring arm. This arm has two holes and is therefore adjustable for rate due to the dual motion ratios of the two hole locations. The front hole would be much softer than the rear hole about 91 pound equivalent rate difference in our case.

We reduced weight in the car by installing lighter components. One of these that made a significant difference in reducing the unsprung weight was this new design of wheel hub from Winters. We lost 3 pounds per wheel.