Because weight transfer in drag racing is critical, finding that fine balance between lift and squat is crucial when setting up the car. The higher in the car that the instant center is located, the higher anti-squat value, and the lower it is the less it has. By strategically placing the instant center at a certain height in relation to the cars’ center of gravity, you can control just how much the car squats or lifts. The anti-squat value mentioned previously is an element related to instant center and is designed into a rear suspension link setup to combat a cars natural tendency to squat under acceleration. The tradeoff is that the tires also unload quicker. The further back and higher in the car that the instant center "intersection" point is, the faster the rear tires will plant to the pavement. The Team Z Fox 9-inch housing allows you to optimize this geometry whether you’re running 10’s or 7’s.
Thus, a fine line in discovering the happy medium between these two action exists in setting up the control arms on your car in order to get the tires planted and keep them planted.
The further back and higher in the car that this intersection point is, the faster the rear tires will plant to the pavement. Obviously finding the instant center of your actual car is going to require more than a pen and a napkin, but you get the idea. With those drawn, locate the point at which these two lines intersect, and you’ve found your instant center. Finally, draw a line right down the center of the rear end housing to the front of the car. Then draw a line from where the lower control arm mounting point on the housing is to the mounting point of the lower control arm on the chassis. To get a better idea of what instant center looks like, grab a pen and a napkin and first draw the rear wheel and the center point of the axle. The instant center of a suspension system is the point in space upon which the suspension links – in this case the control arms – meet.īecause the motiion of the wheel and tires are restricted by the links of the upper and lower control arms, the motion of the wheel and tire forms an imaginary arc in space with an "instant center" of rotation at any point along its path. “That tends to cause a car to hook well in the first 20 to 30 feet of the racetrack, but once the power begins to come in, it’ll unload the chassis due to the both the short instant center and the high anti-squat value.” “On many aftermarket 9-inch housings, as you begin to lower the car and the upper control arms are in the location that they end up on a 9″, what most often becomes the case is a very short instant center in the car,” explained Zimmerman. And the same goes for the lower control arms as well – we have four pickup points on the lowers for adjustability.” With the multiple pickup point options, you can raise or lower the car, and while no one would ever raise it, if you lower the car, you have the ability to adjust the upper control arms. “The geometry on the upper control arms in our new housing is ideal,” explained Zimmerman.”We have multiple pickup points on the top, and most 9-inch housings out there don’t have the correct pickup points.
Zimmerman's 9-inch creation sports multiple pickup points top and bottom for making ample adjustments to your vehicles instant center.