This is from the Griggs Racing (
www.griggsracing.com ) site. Before you get into a discussion about suspensions and/or the components, you will need a basic understanding of the terminology.
"Before going into too much detail, let's take a minute to define some of the terms we commonly use that you might not be familiar with.
Roll Center - Both front and rear suspensions have a Roll Center. This is an imaginary point around which the body of the car will rotate in a turn. The attachment points of the
suspension components determine the Roll Center.
Roll Axis - A line between the front & rear Roll Centers.
CG (Center of Gravity) - The center point of the vehicle's mass.
Understeer - When the front tires lose traction first.
Oversteer - When the rear tires lose traction first.
Neutral Steer - The ideal balance when the front & rear tires gradually give up traction at an equal rate.
Spring Rate - Expressed in pounds per inch, it is the force necessary to compress the spring, i.e. a 200 lb spring requires 200 lbs to compress it 1", 400 lbs to compress it 2", etc.
Motion Ratio - Specifically we usually refer to the relationship between the motion of the wheel and the motion of the spring; i.e. If the spring is half the distance from the control arm pivot as the wheel is, the motion ratio relative to the wheel is .5 to 1.
Wheel Rate - The combined effect of spring rate, motion ratio, friction and/or binding of other
suspension components measured at the wheel
Roll Bind - Any binding of
suspension components that occurs as the body of the car leans over in a turn
Roll Steer - Generally refers to a steering effect on the rear axle as the car leans over in a corner. Caused by the rear
control arms pivoting around their forward mounting point, drawing the axle forward as the arm moves up or down.
Bumpsteer - Toe change as the
suspension moves up & down
Ackerman - AKA "Toe out in turns". When turning the inside tire must turn more than the outer tire because it is turning on a smaller radius
Camber - Expressed in degrees, it is how much the tire leans in or out
Caster - The forward inclination of the spindle or strut - like the forks on a bicycle
Toe - The difference in the distance between the leading and trailing edge of the tires
Specifically the Mustang's shortcomings are:
Too much flex through the floor of the unibody.
Rear
upper control arms whose function is to locate the axle housing laterally as well as control it's rotation (they don't do either very well). They give the car a very high rear roll center, and bind as the car leans into a corner. The binding causes a sudden increase in the wheel rate that results in the Mustang's characteristic "snap" oversteer.
a. The current front
suspension geometry yields only about 2 degrees of caster, which was fine for the skinny whitewall tires that were used on the '78 Fairmont, but is inadequate for today's low profile high performance tires.
b. The front
suspension also has a very low roll center (it can actually be below the ground if the car is lowered too much), which combined with the high rear roll center gives you a very steeply inclined roll axis.
c. The angle at which the front A-arms are mounted promotes brake dive.
d. Bumpsteer-The stock
suspension has too much bumpsteer.
e. Ackerman-The steering rack is not positioned correctly, and does not provide enough toe out while turning, causing the outer edge of the outside tire to drag through the turn."