380 Auto Suspension and Steering Copyright by Goodheart-Willcox Co., Inc. should be turned to obtain the correct camber and caster. Th en, remove the nuts and lower the tower until the mount- ing studs are below the body holes. Turn the tower until the studs line up with the proper holes. Th en, raise the strut tower and reinstall the nuts. Note that the adjustment is limited and that only four strut tower positions are possible. Caster and Camber—Conventional Suspensions On most vehicles with conventional suspensions, camber and caster adjustments are made at the upper or lower con- trol arm. Th ere are three main ways of adjusting the position of the control arm: shims, slotted holes, and eccentric cams. On vehicles that use a wishbone or A-arm–type con- trol arm, caster and camber can be adjusted at the same time. Since caster and camber adjustments aff ect each other, caster and camber should be checked and adjusted together. Th e technician must calculate the change made to both caster and camber. For instance, moving the rear of the upper control arm outward moves the upper ball joint for- ward and makes caster more negative, Figure 17-43. How- ever, it also moves the ball joint outward, making camber more positive. Some control arms are designed with the ball joint off -center, as in Figure 17-44. Adjusting one end of the control arm has more eff ect on the camber, while adjusting the other end has more eff ect on caster. On older rear-wheel drive domestic cars and current light trucks, shims are used at the front and rear of the upper control arms. See Figure 17-45. To make adjustments on these vehicles, loosen the bolts holding the pivot bar to the frame. Th en, add or remove shims as necessary. In many cases, adding or removing a shim from one side of the control arm adjusts camber and caster in one step. Shims thickness varies widely, from 1/32″ (0.03 mm) up about 1/4″ (0.63 mm). Th is wide variety in shim sizes makes exact adjustment possible. Spot weld Plate MacPherson strut FRONT Goodheart-Willcox Publisher Figure 17-42. A MacPherson strut tower plate that is spot welded to the body mount. To adjust alignment, first drill out the spot welds. Move the strut to obtain the desired setting, and torque fasteners to recommended specifications. Ball joint Top of tire Upper control arm FRONT Hunter Figure 17-43. Moving the rear of the upper control arm outward moves the upper ball joint forward, producing a negative caster change. Frame Shims Convex washers Centerline of upper control arm Offset ball joint Upper control arm FRONT Hunter Figure 17-44. An upper control arm with an off-center ball joint. Locknuts Frame Shims Hunter Figure 17-45. Decreasing caster by moving a rear shim to the opposite side. A 1/16″ shim creates about 1/2° of caster change on this assembly.