With the left side mounted...
With the left side mounted lower, the distance the axle moves rearward is greater by a small amount than the right side. In tests and through calculations, we arrived at a movement of 0.050-0.060 inch of movement of the left over the right. This provides just enough bite to help generate more traction without causing the car to be too tight and push.
AntiSquat
Antisquat is a geometric suspension design that utilizes the torque that is transferred to the rearend and tries to rotate the differential. On a three-link car, the third link (upper link mounted above the center of the rearend housing) can be mounted at an angle with the front mount lower than the rear mount so that when the car is accelerating, the force caused by the pinion gear trying to climb the ring gear causes the link to try to straighten out. Since the rear of the link that is mounted to the rearend can't move vertically, the front mount can exert an upward vertical force that resists the squat that comes from weight being transferred to the rear under acceleration.
Antisquat enhances rear traction in two ways, first by helping keep the rear of the car higher and with that the center of gravity. This promotes more load transfer. And second, by keeping the rear spoiler higher due to less squatting.
Load transfer is directly related to the height of the CG, and the higher it is, the more load transferred we have to the rear under acceleration. So, a higher CG promotes traction as more load is transferred while under acceleration. Along with that, a higher rear spoiler catches more air and produces more aero downforce and drag for added grip at the rear tires.
There is no truth to the theory that the third link produces mechanical downforce on the rear tires through the rearend. Any force put on the rearend by virtue of the link wanting to straighten out is offset by the reduced compression in the springs and the tradeoff is even. For every action, there is an equal and opposite reaction. We can't pull weight from out of the sky, so as we stated, all added load comes from increased load transfer from the higher CG and/or more aero downforce from a more efficient rear spoiler.
Contrary to popular belief,...
Contrary to popular belief, pinion angle shouldn't be measured relative to the ground. The important measure is the difference in angle between the pinion shaft and the driveshaft. Excess angle here and at the transmission shaft end of the driveshaft causes a mechanical reduction in the amount of power that reaches the rear wheels. The two angles should be nearly equal and opposite in direction in order for the system to work efficiently.
Rear Geometry
Asphalt cars merely need to maintain a straight ahead attitude when cornering, but dirt cars must steer the rearend to the right on dry slick tracks to develop a more sideways attitude which will point the car in the right direction to be better able to get off the corners. In past years, the drivers on dry slick tracks would need to throw the car sideways in the turns and in the process break the rear tires loose in order to point the car.
When it came time to get back into the throttle, the tires had already lost traction and all that happened was that the tires spun producing little forward bite. With the advent of radical rear steer geometry, the cars will now roll over, the rearend will steer to the right to point the car, and the rear tires will maintain grip with the track surface and be ready to provide forward bite when the driver gets back into the throttle.
The improved technology related to the front end geometry and moment center has helped the dirt cars develop better grip in the front and we now see less rear steer, especially with the tighter conditions. This improves mid-turn speed and helps promote bite off the corners.
Power Steer
A fairly new concept for added bite on asphalt involves a geometric design that will produce rear steer upon application of power. We can utilize a certain type of rear suspension to create rear steer only under acceleration. In the three-link rear suspension system, if we use a pullbar, lift arm, or other similar device that allows the rearend to rotate under acceleration, we can steer the rearend to the left only while the car is accelerating.
As the rearend rotates under power with the pinion moving upwards, the whole rearend will move rearward. If the lower control arms are mounted different distances from the axle, then one side of the rearend will move farther than the other. If the left-side trailing arm is mounted lower than the right-side trailing arm, then the LR wheel will move rearward more so than the RR wheel and this results in rear steer to the left which will tighten a car off the corners.