Over the years, racers have discovered that applying the effects of antisquat (A/S) improv
There are many dynamic effects related to chassis setup that have been discovered and applied over the years to improve the way our cars perform. Experienced crew chiefs know which effects cause which results. We need to know more about how these various effects work. Antisquat (A/S) is one of those mechanical tools that can add traction off the corners when used properly.
A/S is associated mostly with three-link rear suspension systems in which the upper third link is mounted at an angle to the ground with the frontend of the link attached lower than the rear Heim. There is also A/S effect from lift arm devices as well as, to a limited degree, the truck arm suspension systems. We will illustrate how the effect works using the three-link system.
Upon acceleration, the rear pinion gear tends to climb the ring gear in the differential, and this causes the rearend to rotate in a clockwise direction when viewed from the left side. There is a considerable force applied to the third link of the three-link system upon acceleration that pulls on the bar, trying to stretch it. This is the origin of the term pull bars, which is commonly used to refer to links that have torque absorbing springs or a rubber disk.
There are usually several holes in the brackets for the upper and lower control arms so th
The lower trailing arms have a small effect on A/S. They are usually mounted fairly level, up to two or three degrees, and are in compression during acceleration. Because the angle of these links is critical to rear steer characteristics and therefore not considered an adjustable item, we only speak of regulating the angle of the third link to adjust the amount of A/S in our cars.
It has been assumed over the years that by applying A/S to rear suspensions, more weight is applied to the rear tires by the mechanical effect produced through the third link. This is not true. The mechanical effect of A/S causes a portion of the load transfer associated with acceleration to be applied to the third link instead of the rear springs. This means we exchange some of the transferred load off the rear springs and onto the rearend where the link is attached. Since this is an equal tradeoff, there is no more load on the rear tires than before.
The statement that for every action (the A/S forces applying a vertical load to the rearend) there is an equal and opposite reaction (the removal of load from the rear springs) means that there cannot be additional load on the rear tires. This is understandable, because where would the added load come from? In the mechanical world, we cannot receive additional load without taking the same amount of load from somewhere else. So we receive the load from the action of the A/S, and it is taken from the rear springs, to ultimately find itself on the rear tires.
Let's look at it another way. If we had zero A/S effect, the car would transfer a certain load or weight onto the rear springs as we accelerated, the springs would compress to carry the added load, and the car would squat. If we applied 100 percent A/S (meaning the effect would prevent the car from squatting at all upon acceleration), then the springs would not have compressed and therefore would not carry any more load. The load that would have been carried by the springs is now applied to the rearend through the third link because it has to go somewhere.
There are several ways to adjust the magnitude of the force applied to the rearend through the third link. One is the angle of the third link, and another is the distance between the upper link and the lower links. The greater the distance between upper and lower mounts, the less mechanical leverage the system has, and therefore the less A/S effect.