CHAPTER 74 Alignment

© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only

Publisher

The Goodheart-Willcox Co., Inc.Tinley Park, Illinois

by

Russell Krick


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

(12 Topics)


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


The main purpose of wheel alignment is to make sure the tires roll without scuffing,

slipping, or dragging under alloperating 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)


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


Caster

A shopping cart caster illustratesnegative caster


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


Positive Caster

Most common on vehicles withpower 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


Negative Caster

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


Caster Measurement

Measured in degrees, from true vertical


Caster-Road Crown Effect

Road crown is the normal slope toward the outer edge of the road surface


Road crown causes the weight of the vehicle to pull it 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

most negative caster

Caster-Road Crown Effect


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

Camber affects tire wear


Purposes of Camber

Prevent tire wear on the outer or the 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


Camber Measurement

Measured in degrees, from true vertical


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 Toe affects tire wear


ToeToe-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)


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, partreplacement is needed


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


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


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 adjustment


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


Caster, camber, and toe are the three commonly adjustable wheel

alignment angles


Caster/Camber

Adjustment


Caster/Camber Adjustment


Toe Adjustment

Changing the tie-rod length on a

rack-and-pinion unit


Changing the tie-rod length onlinkage-type steering

Toe Adjustment


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


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 in one machine


Wheel Alignment Tools


Wheel Alignment

Tools

A. Steering wheel lock

B. Brake pedal depressor


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

Turning Radius Gauges


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


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 Gauges


Caster-Camber GaugeMounting


Used to compare the distance between the front and rear of a vehicle’s tires for

checking toe adjustment

Tram Gauges


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 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


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



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



This monitor is displaying alignment angles with instructions for adjustment


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

CHAPTER 74 Alignment

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