Modern Automotive Technology PowerPoint for by Russell Krick Publisher The Goodheart-Willcox Co., Inc. Tinley Park, Illinois

Chapter 74 Wheel Alignment

Contents Wheel alignment principles Caster Camber Toe Steering axis inclination Setback Toe-out on turns (turning radius) (Continued)

Contents Tracking Prealignment inspection Adjusting wheel alignment Wheel alignment tools and equipment Alignment machines Road test after alignment

Wheel Alignment Principles The main purpose of wheel alignment is to make sure the tires roll without scuffing, slipping, or dragging under all operating conditions

Alignment Angles Six fundamental angles are needed for proper wheel alignment: caster camber toe steering axis inclination toe-out on turns (turning radius) tracking (thrust line)

Caster Forward or rearward tilt of the steering axis (steering knuckle) when viewed from the side of the vehicle Controls the tire’s load distribution in relation to an imaginary centerline drawn through the spindle support Caster does not affect tire wear

A shopping cart caster wheel illustrates negative caster

A bicycle wheel represents positive caster

Purposes of Caster Aid directional control Cause the wheels to return to the straight-ahead position Offset road crown pull (steering wheel pull caused by the hump in the center of the road)

Positive Caster Tilts the top of the steering knuckle toward the rear of the vehicle Helps keep the wheels traveling in a straight line When the wheels are turned, it lifts the vehicle The vehicle’s weight tends to push the wheels back to the straight-ahead position

More common on vehicles with power steering Positive Caster More common on vehicles with power steering

Negative Caster Tilts the top of the steering knuckle toward the front of the vehicle The wheels will be easier to turn The wheels will tend to swivel and follow imperfections in the road

May be used on vehicles with manual steering, to ease steering effort Negative Caster May be used on vehicles with manual steering, to ease steering effort

Measured in degrees, from true vertical Caster Measurement Measured in degrees, from true vertical

Caster and Road Crown Effect Road crown is the normal slope toward the outer edge of the road surface

Caster and Road Crown Effect Road crown causes the weight of the vehicle to pull the vehicle away from the center of the road Caster is commonly used to offset the effect of road crown The right front wheel may be set with slightly more positive caster than the left the vehicle pulls toward the side with the more negative caster

Camber Inward or outward tilt of the wheel and tire assembly when viewed from the front of the vehicle Controls whether the tire tread touches the road surface evenly Affects tire wear

Purposes of Camber To prevent tire wear on the outer or inner tread To load the larger inner wheel bearing To aid steering by placing the vehicle’s weight on the inner end of the spindle

Positive and Negative Camber Positive camber the tops of the wheels tilt outward when viewed from the front most manufacturers specify a positive setting of about 1/4º to 1/2º Negative camber the tops of the wheels tilt inward when viewed from the front

Positive and Negative Camber

Measured in degrees, from true vertical Camber Measurement Measured in degrees, from true vertical

Toe Difference in distance between the front and rear of the left- and right-hand wheels Measured in inches or millimeters Controls whether the wheels roll in the direction of travel Affects tire wear

Toe Toe-in: wheels are closer at the front than at the rear Toe-out: wheels are farther apart at the front than at the rear

Rear-Wheel-Drive Toe Settings Rolling resistance and steering system play tend to cause toe-out when driving Toe-in compensates for these factors By adjusting the front wheels for a slight toe-in, the wheels and tires roll straight ahead when driving Typical setting: 1/16"–1/4" (1.6 mm–6 mm)

Front-Wheel-Drive Toe Settings The front wheels are pushed forward by engine torque, causing the wheels and tires to toe in To compensate for this action, front-wheel-drive vehicles normally have the front wheels adjusted for a slight toe-out Typical setting: 1/16" (1.6 mm)

Steering Axis Inclination The angle, away from the vertical, formed by the inward tilt of the steering axis (ball joints, king pin, or MacPherson strut tube) Aids directional stability by helping the steering wheel return to the straight-ahead position Does not affect tire wear

Steering Axis Inclination If the angle is incorrect, part replacement is needed

Setback One front wheel is set farther back from the front of the vehicle than the other front wheel with positive setback, the right wheel is farther back than the left wheel with negative setback, the left wheel is farther back than the right wheel Excessive setback will cause pull

Setback Manufacturing tolerances generally allow a small amount of setback Excessive setback is usually the result of collision damage

Toe-Out on Turns (Turning Radius) Amount the front wheels toe-out when turning corners As the vehicle corners, the inside tire must travel in a smaller radius circle than the outside tire The inside wheel turns sharper than the outside wheel

Toe-Out on Turns

Toe-Out on Turns Eliminates tire scrubbing and squealing by keeping the tires rolling in the right direction during turns Not an adjustable angle If the angle is incorrect, it indicates bent or damaged steering parts

Tracking Position or direction of the two front wheels in relation to the two rear wheels With the proper tracking, the rear tires follow in the tracks of the front tires With improper tracking, the rear tires do not follow the tracks of the front tires increased tire wear, lower fuel economy, and handling problems can result

Tracking

Prealignment Inspection Before attempting wheel alignment, make sure all steering-related and suspension-related parts are in good condition It is impossible to properly align the wheels on a vehicle with worn or damaged parts

Prealignment Inspection Points Check for the following: loose wheel bearings wheel or tire runout worn tires tires of different sizes and types incorrect tire inflation worn steering or suspension components incorrect curb height and weight incorrect cradle alignment

Reading Tire Wear

Cradle Alignment The cradle is the strong metal structure bolted to the frame rails on the body holds the lower control arms, steering rack, and engine in alignment in the body Loosening and moving the cradle can alter alignment Alignment holes may be provided in the cradle and body to assure proper alignment

Adjusting Wheel Alignment Caster, camber, and toe are the three commonly adjustable wheel alignment angles

Caster and Camber Adjustment

Caster and Camber Adjustment

Changing the tie-rod length on a rack-and-pinion unit Toe Adjustment Changing the tie-rod length on a rack-and-pinion unit

Changing the tie-rod length on a linkage-type steering system Toe Adjustment Changing the tie-rod length on a linkage-type steering system

Centering Steering Wheel

Adjusting Rear Wheel Alignment Some vehicles have provisions for rear wheel alignment Rear wheel alignment problems can occur due to component wear or damage Procedures for rear wheel adjustment vary

Adjusting Rear Wheel Alignment On this axle, shim placement changes alignment angles

Wheel Alignment Tools and Equipment Various equipment and special tools are needed The most basic equipment includes the turning radius gauge, the caster-camber gauge, and the tram gauge Alignment racks integrate the functions of all these gauges into one machine

Wheel Alignment Tools

Wheel Alignment Tools A. Steering wheel lock B. Brake pedal depressor

Turning Radius Gauges Measure how many degrees the front wheels are turned right or left Commonly used when measuring caster, camber, and toe-out on turns The gauges may be portable or mounted on the alignment rack

Using Turning Radius Gauges Center the front wheels of the vehicle on the turning radius gauges Pull out the locking pins so the gauge and tire turn together The pointer on the gauge will indicate how many degrees the wheels have been turned

Checking Toe-Out on Turns Center the front wheels of the vehicle on the turning radius gauges Turn one of the front wheels until the gauge reads 20º Read the number of degrees showing on the other gauge Check both the right and left sides both sides must be within specs

Caster-Camber Gauges Used with the turning radius gauge to measure caster and camber in degrees Secured on the wheel hub magnetically or fastened on the wheel rim Caster and camber are adjusted together since one adjustment may affect the other

Caster-Camber Gauge Mounting

Tram Gauges Used to compare the distance between the front and rear of a vehicle’s tires for checking toe adjustment

Alignment Machines The alignment machine consists of a rack, console, and related parts Rack consists of a lift, turning radius gauges, and equipment for measuring alignment angles Console consists of a color monitor, keypad, and computer

Alignment Machine

Console This console provides training, instructions, specifications, and feedback when doing wheel alignment

Software Alignment equipment software contains computer instructions, equipment operating instructions, and alignment specifications When installed in the computer, the software will help you adjust all alignment angles quickly and easily Usually stored on a CD-ROM

Alignment Heads Mount on the vehicle’s wheels Brackets are used for mounting the alignment heads on the wheels Use lasers or proximity sensors to compare the alignment of each wheel Used to check caster, camber, and toe

Alignment Head

Using Alignment Equipment Always follow the operating instructions provided by the manufacturer Drive the vehicle up on the lift Carefully center the front tires on the turning radius gauges Block the rear wheels Mount the alignment heads on the wheels

Using Alignment Equipment Turn on the alignment console Follow the computer prompts After you identify the vehicle, the computer will retrieve stored data about performing an alignment on the vehicle As you make adjustments, the equipment will monitor the changes in the alignment angles

Using Alignment Equipment This technician is using a four-wheel alignment machine with a color monitor

Using Alignment Equipment This monitor is displaying alignment angles with instructions for adjustment

Road Test after Alignment Always road test the vehicle to check your work Drive on level pavement Check the steering wheel alignment Feel for steering wheel pull Check for other problems, such as noise or vibration

Noise and Vibration Diagnosis Chart