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Chapter Four: Use of Wheels, Tires and Adjustment of Wheel Alignment
It is not difficult to understand the definitions of different angles and their functions, while it is not that easy to apply these theories on maintenance of four-wheel aligner and chassis to solve problems occurred. The reason lies in chassis structure, i.e. aligning angles of four wheels are related to mechanical structure of chassis. Examples: 1. Changing toe-in angle will also change camber angle: since the wheel will rotate when changing toe-in angle, the camber angle will also be changed. The bigger the caster angle is, the bigger the camber angle changes. 2. Regulating caster angle also changes wheel inclination: the upper pivot of steering shaft will move forward or backward when increasing or decreasing caster angle, and so will the lowest pivot of steering shaft, i.e. the tire. Therefore, increasing or decreasing caster angle will move front wheels forward or backward and further change the axle inclination. To allow the free forward or backward movement of front wheels, the swivel adopted must be able to move forward or backward, too. 3. Changing camber angle will meanwhile change toe-in angle, while changing toe-in angle will also change camber angle as well. The adjusting method of camber angle may differ with different suspension structure. When moving upper or lower revit leftward or rightward, not only the camber angle but also the toe-in angle will be changed. Even the camber angle is calibrated, the driving may still be unsmooth due to the changed toe-in angle. One problem is fixed, but another appears. 4. Changing rear wheel toe-in will affect front monowheel toe-in: rear wheel toe-in angle decides rear wheel axis of thrust angle. Modern four-wheel alignment adopts axis of thrust alignment to deside front wheel toe-in. Note: When adjusting four-wheel alignment, rear wheels shall be adjusted first, and then front wheels. Adjusting order for rear wheels: camber angle, toe-in angle, etc.; adjusting order for front wheels: caster angle, camber angle, toe-in angle, etc. |