The best way to visualize caster is to picture a shopping cart caster. The pivot of this type of caster, while not at an angle, intersects the ground ahead of the wheel contact patch. When the wheel is behind the pivot at the point where it contacts the ground, it is in positive caster. Picture trying to push a shopping cart and keep the wheel ahead of the pivot. The wheel will continually try to turn from straight ahead. That is what happens when a car has the caster set too far negative. The factory caster setting for classic Ford cars calls for a small amount of positive caster.
The third dimension of our alignment is the toe measurement. This is the difference in the center to center distance between the front of the tires and the back of the tires. It is measured in fractions of an inch and is usually set close to zero, which means that the wheels are almost parallel to each other. Toe-in means that the fronts of the tires are closer to each other than the rears. Toe-out is just the opposite. An incorrect toe-in setting will cause rapid tire wear. For racing purposes, toe-in is subtracted or eliminated to aid quicker response when cornering. However, a vehicle aligned this way won't be much fun to drive on the freeway.
Bushings: Stock Versus Modified
It's a fact that when Ford designed the original suspension many important moveable junctures or pivot points had rubber bushings as original equipment. Both upper and lower control arms were attached to the car using a bushing with a steel center and a rubber jacket. While the rubber dimension of these components reduced vibration and promoted a smoother ride, after a certain amount of time these bushings would begin to compress and come out of round. In addition to losing the correct alignment adjustment, a certain amount of play was created, allowing the component to move around freely-not the best of circumstances for correct vehicle alignment or concise steering. Now there's a great bolt-in alternative from Fly-Ford Racing that gives a near-stock appearance without any suspension or frame modifications.