Caster is often mentioned when you are getting an alignment. Caster refers to the angle that is created by the steering pivot point in relation to the front and back wheel of the vehicle.
You will have a positive caster if the line created is forward from the center of the wheel and negative if the line is facing backwards. Positive and negative casters each have their own strengths and weaknesses. With positive caster the driver will notice better stability especially at higher speeds but will also feel increased tire play when cornering which in turn will create a greater steering effort.
When the caster angle is not proper for the vehicle in question you may also notice a general unpleasant handling experience, car drifting to one side of the road, increased uneven tire wear, and heavy steering in certain situations while experiencing light steering in others. When the caster is adjusted properly it allows for optimized tire grip and dramatically improves handling.
Many years ago, suspension alignments were not offered and were not very well known. Depending on the design of the car and driving habits some cars experienced issues from improper caster angles more than others did. The cars that had most visible issues were known as “pull to the left” cars and “pull to the right” cars. These sayings are still used today. If you’re car is a “pull to the left” or “pull to the right” car, be sure to get an alignment as soon as possible. The longer you drive on a poorly aligned car, the more likely you are to damage the suspension components and cause uneven and increased tire wear which as we know are not cheap!
Here is an illustration of negative, neutral, and positive caster: