Camber Gain

If negative camber increases the size of the contact patch during cornering—and therefore increasing grip—camber gain expands upon that concept. Proper chassis tuning can result in a suspension that yields an increase in negative camber as body roll increases, a condition known as camber gain. “One of the biggest performance limitations of a stock suspension is the limited amount of camber gain that can be achieved with them. In fact, compressing the suspension in many muscle cars results in positive camber, which is the exact opposite of what you want,” says Roadster Shop’s Jeremy Gerber. “There isn’t much you can do to increase camber gain with a stock suspension because it’s difficult to move the pickup points around. You can lower the attachment point of the upper control arm, but that’s about it. With an aftermarket frame, however, you can radically change the length of the control arms, and relocate the pickup points. A car like a stock C6 Corvette will pick up half a degree of negative camber for every inch of suspension travel. We set up our frames to pick up 1 degree of negative camber for every inch of travel.”

Instant Center

Conceptualizing instant center is best done by looking at the side profile of a car. If you drew a line from the back of the rear control arms to the front of the rear control arms, then extended the lines to the front of the car, a car’s instant center is the point where those lines intersect. Raising the instant center, or moving it farther rearward, results in a chassis that transfers weight from the front to the rear more quickly. Lowering the instant center, or moving it farther forward, decreases weight transfer. “There are lots of opinions on where the instant center should be positioned, but we’ve learned a lot through track testing,” RideTech’s Bret Voelkel explains. “With our four-link rear suspension systems, we have had positive results by running the lower control arm parallel to the ground, and angling the upper control arms downward 2 to 3 degrees. This puts the instant center right at the back of the crankshaft, and gives a car excellent forward bite. If the upper and lower control arms are close to parallel, it puts the instant center way out in front of the car and compromises traction.”

Roll Center

The point in space where the suspension and body rotates as a car leans from side to side is the roll center. If plotting a scale drawing of a suspension on paper, the first step in determining the roll center is to establish the instant center location based on the angles of the control arms. Next, a line must be drawn from the left and right contact patches of the tires to the instant center. The intersection point of these two lines is the roll center, which can be located above or below the ground. “Moving the roll center changes the roll stiffness of a vehicle,” Matt Jones of AME says. “The farther away from the center of gravity the roll center is, the more a car will roll. Raising the roll center reduces body roll. That said, the roll center couldn’t be moved much at all within the confines of stock suspension pickup points.”