1993 Ford Mustang - Three-Step Program

Instant Center
"Looking at the side profile of a car, if you drew a line from the back of the control arms to the front of the control arms, and extended those lines all the way to the front of the car, where the lines intersect is the instant center. The higher and further toward the back of the car the instant center is, the more quickly it will transfer weight. The lower and further forward the instant center is, the more slowly it will transfer weight. Unlike a full-race four-link, the upper control arm pickup points on a Fox Mustang's triangulated four-link are not adjustable. Consequently, the only way to adjust the instant center is with a set of lower control arm relocation brackets. If the control arms are parallel to the ground or point downward, then the instant center will be too low, making it difficult to transfer weight rearward. This forces the rear suspension to lift more weight than it can handle, compromising weight transfer and reducing traction. If the control arms point too far upward, then the instant center will be too high. The car will shift weight too quickly and hook up hard, but then the rear suspension will unload and smoke the tires. The goal is to find a happy medium that allows weight to transfer efficiently without unloading the rear tires too quickly as it goes down the track." -Bill Buck