...as well as the four-link...
...as well as the four-link setup (B) are set so that the birdcage ends at the top and bottom will move in opposite directions as the chassis compresses on the right side and rebounds on the left side. This keeps the axle tube in the same position front to rear to provide zero rear steer.
Hobby Stock (HS): We might run a stiffer right-front (RF) spring and a stiffer right-rear (RR) spring. A typical spring layout would be: left-front (LF) = 800; RF = 900 (or a 750 with a full spring rubber, if spring changes are not allowed); left-rear (LR) = 200; RR = 225 (or a 175 with two full spring rubbers). The rear ride height would be set as low as possible, as this would raise the rear moment center and lower the CG to reduce the rear roll angle versus the front roll angle to help balance the setup. Any moveable weight would be mounted low and left in the car. If you have a choice, run tires with large grooves such as the all-terrain types for mud and snow. Run a higher pressure in all of the tires.
Late Model (LM): A similar situation would apply to the LM car. For now, use a stiffer (RR) spring with a high Panhard bar mounted on the right side for consistency. Keep the weight low and to the left, and use tires with wide grooving to release the wet mud easily. Keep the air pressure high.
The Late Model setup is very...
The Late Model setup is very similar to an asphalt setup when the dirt has a lot of traction. The car can be driven straight ahead, deep into the corners, and hard off the corner. The right-side chassis Panhard mount technique makes the car more stable for the high g-force conditions. We will move the bar over to the left later on.
A typical setup might be: LF = 400; RF = 450; LR = 225 (400 pounds swing arm); RR = 275 (500 pounds swing arm); 56 percent left-side weight; Panhard bar at 11 inches left and 12 inches right, mounted to the right side of the chassis; and no front Ackermann with zero rear steer. On this car, we would have already moved the upper mounts for the rear shock/springs out as much as possible to reduce the rear spring angles.
On a track that has good moisture and is smooth, the car will be easy to control going through the turns and the speeds will be high. We keep the low CG (mount the weight low in the car) to reduce weight transfer to the right side to help maintain left-side weight in the turns.
HS: We could maintain the previous setup as the track begins to smooth out, but it will keep a considerable amount of grip. We could raise the rear ride height an inch or so to be ready if the track begins to dry out some and affect bite off the corner. Keep the all-terrain tires and lower the pressures a bit.
As the track goes more toward...
As the track goes more toward the slick condition, we begin to soften the right-side springs and make changes to the rear moment center heights.
LM: These conditions are the fastest you will encounter. The car should enter, go through the middle, and come off the corners going straight ahead and balanced in the overall setup. We will make some changes to the previous spring setup. A typical setup might be: LF = 350; RF = 375; LR = 175 (325 pounds swing arm), RR = 225 (400 swing arm); 56 percent left-side weight; Panhard bar at 11 inches left and 12 inches right; and no front Ackermann with zero rear steer.
We will need to change to tires that are harder, with less gap and more surface rubber. The air pressure must come down some, but do not run soft on air at this point. Zero rear steer is essential now because our dirt car will handle much like an asphalt car. The driver can drive straight into the corner, brake harder, and get back into the throttle sooner than at any other time of the day.
We also move the Panhard bar...
We also move the Panhard bar chassis mount over to the left side at this point.
Under these conditions, teams using softer RR springs with Panhard bars high on the left side and low on the right side and with plenty of rear steer will find trouble. In short, they will be all over the track.
Once the track has hardened, it will quickly continue to change toward black and then to slick. The hardened track condition may only occur for one heat or so. We might want to anticipate the dry and slicker conditions coming now for lack of time later.
HS: As the track begins to dry out, the surface will start to become black and a little slick. We can now begin to soften the setup somewhat and change the RF spring to an 800-pound (rated) spring or remove the RF full spring rubber and replace it with a half rubber. The RR spring should change to a 200-pound (rated) spring or pull one rubber out. Raise the rear ride height another inch. This does two things: It lowers the rear moment center and raises the car's CG. The tires can be changed to more of a street performance tread with slightly lower pressures.