The leaf spring suspension...
The leaf spring suspension system usually has fixed mounts in the front and therefore no adjustment for amount of rear steer. The rearend stays mostly square in the car throughout the lap. The feedback we hear from the racers is that the leaf spring rear suspension is good on tacky or wet tracks.
Tuning On Dirt With Rear Steer
We should learn to read the conditions of the track and tune the amount of rear steer. We need much less, maybe none, for tacky and wet conditions and then we can add some RS as the track gets slicker. On extreme dry slick conditions, many teams use a lot of RS to the right. This is accomplished by causing the RR wheel to move back and the LR wheel to move forward as the car rolls and hikes up on the left side. Soft springs, a high center of gravity, a left chassis-mounted track bar running at a high angle, and easy up shocks on the left side all promote the body roll that produces rear steer to the right.
The metric four-link suspension...
The metric four-link suspension has two links above the rearend and two links below the rearend. They are angled from a top view to prevent the rearend from moving side to side as the chassis rolls. With this system, the rearend stays located by virtue of the opposing angles of the upper and lower links. The roll center in this system is very high compared to other systems. To get the rear to roll, teams use a much softer right rear spring than the left rear. Using a stiff right rear spring will cause the car to be very loose.
What we need to think about is, do we need a lot of rear steer? In my observations, and this has been fortified by comments I've received from some of the top drivers in Dirt Late Models, a flatter and more straight ahead running car will do very well in 85 to 90 percent of the conditions teams encounter as they travel the circuit. There are times when changes must be made in small amounts for drier conditions and times when the tracks are so dry and slick the teams must go to extremes.
For most events and for most of the race day, minimal rear steer will produce a more consistent lap. Some tracks will yield only so much speed in the turns no matter what you do, but at the end of the day, most will agree that the driver who makes the least mistakes usually has the best chance of winning. So, consistency counts for a lot, just ask Mr. Moyer. When racing on dirt, watch the conditions and be prepared to make changes accordingly, not just to the setup, but also related to rear steer. That way, the car will stay as fast and balanced as it can be throughout all of the changing conditions.