Caster and camber are settings that affect a car's steering and ultimately its driving performance. Altering these settings can affect how the car performs and will also affect the "feel" of the steering. Drivers react differently to caster and camber settings, so car manufacturers have conducted extensive research into both to come up with specific settings for their cars.
Caster is the angle of offset between the upper and lower ball joints on a car's steering system. This setting is measured in degrees. If you were to draw a line from the ground through the bottom ball bearing, center of the wheel and top bearing, then draw one from the intersection of the ground and this line, perpendicular to the very top of the tire, the offset angle would be the caster.
When a car has positive caster, the top bearing is positioned farther forward than the lower one. This gives the angle of caster a forward-leaning position. When the lower bearing is positioned farther forward than the upper bearing, the car has a negative caster. In this situation, the car is more stable when it moves forward in a direct line. That is because the wheel's position in relation to the turning axis keeps it in line.
Caster affects how easily the car turns to one side or the other. This is due to the position of the bearings over the wheel center. When they are farther offset, more caster is generated because of the distance between the turning pivot and the wheel. If you can imagine a force that draws the wheels into line as they are pulled along, you can imagine how this works. If you were to drag a wheel on a string behind you, eventually the wheel will fall in line with your path. That is the relational force of caster.
Camber is the position of the wheels on vertical axis. Wheels that have camber are either tilting toward or away from the car. Just as you would lean a tire to one side or the other by pushing it and holding on edge, camber does the same. When a wheel is tilted on an angle so the top is closer to the car than the bottom, it naturally grips the road better when it turns. Camber is often used in race cars that need more grip while performing high-speed turns. Wheels on one side can be tilted so the car can make more left or right turns. It can also be used to some degree in modern sports cars to add a performance edge.
Camber alone can be used to help a race car perform better through turns when the course has many left turns. Tilting all the wheels to the left (so the top leans left) produces better performance on left-handed turns. Caster settings also play a role. If you set different caster settings on opposing wheels, then the car will also lean to the left. This can be achieved by setting one top bearing forward, and one slightly backward. The vast range of settings is inexhaustible, and it is something pit crews and engineers work with daily to eke every ounce of performance out of their cars.
