Chapter 17 Wheel Alignment Procedures 371 Copyright by Goodheart-Willcox Co., Inc. Locking Brakes Lock the brakes with a brake pedal depressor. Th is prevents excessive wheel movement while checking caster. At this time, you should fi rmly apply the parking brake. If the vehi- cle has an automatic transmission, shift it into park. Measuring Alignment Aft er all preliminary steps have been completed, the align- ment can be measured. Th is should be done in the order given in the following sections. Checking Camber and Toe If the alignment machine has a display screen, front and rear camber and toe are shown on the screen, Figure 17-20. On most machines, this is an automatic process once the heads have been compensated. On older alignment machines using lighted heads, the front camber and toe are shown by the position and slant of the light lines on the display boards. If necessary, record the camber and toe readings. Note: You should check the rear-wheel alignment, even if the rear axle cannot be realigned. Knowing the position of the rear axle is often necessary, especially when the steering wheel cannot be centered, or when the driver is concerned with rear tire wear. Checking Caster To check caster, be sure the brake pedal depressor is applied. Most alignment equipment manufacturers specify that the heads be locked into position (unable to pivot on the mount- ing frame) for the caster check. Turn the wheels to the left and right according to the alignment machine manufacturer’s instructions. Th is can be done by turning the wheels them- selves or by turning the steering wheel. See Figure 17-21. When using the steering wheel to turn the wheels, do not sit in or lean on the vehicle. Th is will change suspension height and aff ect the readings. On some systems, you must turn the steering wheel until the screen indicates that the read- ings have been obtained. On other systems, the turntables must be turned an exact amount, usually 20°. Record the caster reading if the alignment machine does not automatically do so. Note: If caster and camber are within specifications and the vehicle is pulling, the problem may be a defective tire. You may want to swap the front tires from left to right and road test the vehicle before proceeding. If the pull changes sides or is no longer evident, a tire is defective. In almost all cases, the defective tire is on the side of the pull. Alignment rack Turning plate Lexus Figure 17-18. Bouncing the front and rear of a vehicle while it is resting on the turning plates. This permits the vehicle to settle to its normal resting position. Steering wheel holding tool Brake pedal depressor Fusionstudio/Shutterstock.com Figure 17-19. A steering wheel holding tool and brake pedal depressor have been installed. Valentinos71/Shutterstock.com Figure 17-20. A typical alignment screen display.