Editing Caster angle (section)

==Positive caster angle==
The steering axis is angled such that a line drawn through it intersects the road surface slightly ahead of the center of the contact patch of the tire on the pavement by a distance called [[Bicycle_and_motorcycle_geometry#Trail|trail]]. The purpose of this is to provide a degree of self-centering for the steering—the wheel casters around in order to ''trail'' behind the axis of steering. This makes a vehicle easier to control and improves its [[directional stability]] (reducing its tendency to wander). Excessive caster angle will make the steering heavier and less responsive, although in racing large caster angles are used for improving camber gain in cornering. Caster angles over 7 degrees with radial tires are common. Power steering is usually necessary to overcome the jacking effect from the high caster angle.

Some front-end alignment calls for different right-side and left-side caster. This is called cross caster, and the difference is called the spread. Cross camber may also be specified, but not usually both.<ref name=gilles>{{cite book |author=Tim Gilles |title=Automotive Service: Inspection, Maintenance, Repair |url=https://books.google.com/books?id=hUoJAAAAQBAJ&pg=PA1273 |date=24 July 2012 |publisher=Cengage Learning |isbn=978-1-133-42068-2 |pages=1273–}}</ref>