Chapter 17 Wheel Alignment Procedures 387 Copyright by Goodheart-Willcox Co., Inc. computer operated and use sensing devices mounted on every wheel. Th ese devices are called heads. Before performing wheel alignment, talk to the driver to determine why the vehicle was brought in for an align- ment. Road test the vehicle before beginning the alignment. Once you have gathered information from the driver and the road test, drive the vehicle onto the alignment rack. Raise the wheels and check for worn parts. Also, inspect all tires for damage. Check the ride height and look for signs of underbody damage. To set up the vehicle for wheel alignment, the wheels must be free to turn. Th e vehicle must be at its correct curb weight. Aft er obtaining alignment specifi cations, install the alignment heads. If necessary, remove the wheel cover locks and wheel covers then clamp the head to the rim and com- pensate it. Lower the vehicle, making sure the turning plates are centered under the wheels. Next, center the steering wheel and lock the brakes. Bounce the vehicle to place it in its rest- ing position. Aft er all pre-alignment steps have been taken, check camber, caster, and toe. Also, check SAI and toe-out on turns, if necessary. To adjust alignment, begin by adjusting the camber and toe on the rear axle. Typical rear camber and toe adjusting devices are eccentric cams, slotted holes, and threaded rods. On vehicles with four-wheel steering, a special tool may be needed to lock the rear steering gear. On some vehicles, the camber and toe can be set with shims. Set the front alignment aft er setting the rear alignment. Not all adjustments can be made on all vehicles. Never bend or weld suspension or steering parts for alignment. Typical MacPherson strut vehicle adjusting devices are eccentric cams, threaded rods, and slots in the body at the top of the strut tower. Conventional suspensions use cams, shims, or slots at the control arm. On some trucks with solid axles, caster and camber can be adjusted using eccentric bushings. Before adjusting toe, turn the steering wheel from side to side. Center it and install the steering wheel holder. Th en, loosen the tie rod adjusting sleeve bolts or tie rod locknuts. Adjust toe by turning the sleeves or rods to obtain half the needed toe on each wheel. Some vehicles have only an adjuster, and the steering wheel cannot be straightened. Other vehicles have separate adjustments for toe and center- ing the steering wheel. Aft er making all adjustments, recheck front and rear alignment. Check fastener tightness and part position before considering the alignment complete. Th en, remove the alignment heads from wheels and reinstall the wheel covers. Remove the brake pedal and steering locks and back the vehicle carefully from the rack. Make a fi nal road test when the wheel alignment is fi nished. If a problem is found, recheck the alignment. Frames must be straightened when an adjustment is used up. Frame straightening is done by a body shop with the proper equipment. Review Questions—Chapter 17 Answer the following questions using the information provided in this chapter. 1. In your own words, explain why four-wheel alignments must be performed on many modern vehicles. 2. On most cars and trucks, _____ should be the last alignment adjustment. 3. What is the purpose of the alignment rack turning plates? 4. Sensing devices mounted on the wheels to make alignment measurements are called alignment _____. 5. Some older alignment machines use _____ _____ to create readings on a stationary board. 6. Wheel cover locks hold the cover to the _____. 7. Th e brake pedal depressor prevents excessive wheel movement when _____ is being checked. 8. Th e alignment machine has a display screen. Which of the following will not be shown on the screen as soon as the heads are compensated? (A) Front camber. (B) Front caster. (C) Rear camber. (D) Rear toe. 9. Toe-out on turns can be changed by _____. (A) adjusting toe inward (B) adjusting toe outward (C) adjusting SAI (D) changing steering arms 10. Th e tendency of a misaligned vehicle to travel down the road at an angle is called _____ _____. 11. Name three factory devices used to adjust rear camber and toe. 12. Camber and caster are oft en set to specifi cations that cause the vehicle to drift slightly to the left . Why? 13. Which of the following alignment angles is always adjustable at the front wheels? (A) Camber. (B) Caster. (C) SAI. (D) Toe. 14. If a vehicle has an A-arm type upper control arm, which two alignment angles can sometimes be adjusted by moving only one side of the control arm? 15. Before adjusting toe, the steering wheel must be _____.