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© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only
Publisher
The Goodheart-Willcox Co., Inc.Tinley Park, Illinois
by
Russell Krick
© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only
© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only
Wheel alignment principles Caster Camber Toe Steering axis inclination Toe-out on turns (turning radius)
(12 Topics)
© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only
Tracking Prealignment inspection Adjusting wheel alignment Wheel alignment tools and equipment Alignment machines Road test after alignment
© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only
The main purpose of wheel alignment is to make sure the tires roll without scuffing,
slipping, or dragging under alloperating conditions
© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only
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)
© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only
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
© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only
Caster
A shopping cart caster illustratesnegative caster
© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only
Caster
A bicycle wheel represents positive caster
© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only
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)
© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only
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
© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only
Positive Caster
Most common on vehicles withpower steering
© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only
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
© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only
Negative Caster
May be used on vehicles with manual steering, to ease steering effort
© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only
Caster Measurement
Measured in degrees, from true vertical
© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only
Caster-Road Crown Effect
Road crown is the normal slope toward the outer edge of the road surface
© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only
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
© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only
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
© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only
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
© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only
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
© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only
Positive and Negative Camber
© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only
Camber Measurement
Measured in degrees, from true vertical
© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only
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
© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only
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
© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only
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)
© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only
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)
© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only
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
© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only
Steering Axis Inclination
If the angle is incorrect, partreplacement is needed
© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only
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
© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only
Toe-out on Turns
© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only
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
© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only
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
© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only
Tracking
© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only
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
© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only
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
© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only
Reading Tire Wear
© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only
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
© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only
Caster, camber, and toe are the three commonly adjustable wheel
alignment angles
© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only
Caster/Camber
Adjustment
© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only
Caster/Camber Adjustment
© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only
Toe Adjustment
Changing the tie-rod length on a
rack-and-pinion unit
© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only
Changing the tie-rod length onlinkage-type steering
Toe Adjustment
© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only
Centering Steering Wheel
© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only
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
© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only
Adjusting Rear Wheel Alignment
On this axle, shim placement
changes alignment angles
© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only
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
© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only
Wheel Alignment Tools
© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only
Wheel Alignment
Tools
A. Steering wheel lock
B. Brake pedal depressor
© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only
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
© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only
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
© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only
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
© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only
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
© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only
Caster-Camber GaugeMounting
© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only
Used to compare the distance between the front and rear of a vehicle’s tires for
checking toe adjustment
Tram Gauges
© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only
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
© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only
Alignment Machine
© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only
Console
This console provides training, instructions, specifications, and
feedback when doing wheel alignment
© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only
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
© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only
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
© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only
Alignment Head
© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only
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
© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only
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
© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only
Using Alignment Equipment
This technician is using a four-wheel alignment machine with a color monitor
© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only
Using Alignment Equipment
This monitor is displaying alignment angles with instructions for adjustment
© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only
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
© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only