Learning Guide
CHASSIS SPECIALIST
ALIGNMENT FOR INSTALLERS
COURSE NUMBER: W030-01
Chassis Specialist: Alignment for Installers
Notice
Due to the wide range of vehicles makes and models, the information given during the class will be
general in nature and should not be taken as specific to any vehicle/unit. Please consult manufacturer
specifications for the correct number/specifications and repair procedures for the vehicle you are
testing. This document is meant to be used as a guideline only.
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Copyright © 2014 CARS Training Network Inc
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Chassis Specialist: Alignment for Installers
Introduction
OBJECTIVES
Upon successful completion of this segment, the participants should be able to:

Identify abnormal tire wear and understand the common underlying causes

Perform preliminary vehicle inspections including TSB searches

Identify the various types and functions of alignment equipment

Understand alignment angles and adjustment procedures (including special tools required)

Understand the safety precautions for alignments

Perform Two-Wheel Alignments
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Chassis Specialist: Alignment for Installers
Alignment for Installers
In this module we will run through doing a simple alignment. In many cases toe is the only adjustable
angle, but we will describe the common adjustable alignment angles. In the next module we’ll cover
four-wheel alignments, more advanced alignment angles and settings as well as problems.
Purposes of Alignment:

Reduce tire wear

Reduced steering effort

Maximum fuel mileage

Safer vehicle

Improved handling
Reference Lines:
Basis of all alignment angles:

Vertical line

Vehicle centerline

Geometric centerline

Thrust line
How often should an alignment be done?
____________________________________
____________________________________

____________________________________
____________________________________
____________________
Vertical Line
Vertical reference point for each
wheel and reference for:

Camber angle

Steering Axis Inclination
angle (SAI)

Included Angle (IA)
Vertical reference line
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Chassis Specialist: Alignment for Installers
Vehicle Centerline
Longitudinal line splitting vehicle into equal halves
Reference for:
 Geometric Centerline Angle
 Thrust Line Angle
Geometric Centerline:
If a line were drawn through the front spindles, the
geometric centerline would be between the midpoints
of this line and the rear axle.
Reference for correcting geometry (angles) of two
wheels.
Thrust Line:
Line bisecting the rear toe angle.
Possible problems for solid-axle vehicles include:
 Axle offset
 Damage
 Worn mounts
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Chassis Specialist: Alignment for Installers
Wheelbase Difference
The distance between the center of the front
wheels and the center of the rear wheels.
The distance between these two points
should be equal on both sides of the vehicle.
Set Back
The amount by which one front wheel is
further back from the front of the vehicle
compared to the other front wheel.
If the left wheel is further back than the
right, setback is negative.
If the right wheel is further back than the
left, setback is positive.
If the alignment machine doesn’t automatically measure these angles, a
tape measure can be used to measure the wheelbase.
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Chassis Specialist: Alignment for Installers
Basic Angles:

Caster

Steering Axis Inclination (SAI)

Camber

Included Angle (IA)

Toe in and toe out

Toe out on turns
Other Angles and Diagnostics

Steering Axis Inclination (SAI)

Included Angle (IA)

Toe-out on turns

Set Back
Steering Axis Inclination (SAI)

The inclination of the top of the
steering axis in relation to the vertical, observed from the
front of the vehicle

This angle is usually between 5 and 15 degrees.

Allows the steering wheel to return
to the center after having turned

Reduces the effect or reaction of the suspension when
braking
SAI: The angle between the true vertical and the incline of the
steering pivots. This image also shows a zero scrub radius.
Scrub Radius

The point where SAI angle
and the tire centerline meet

May be either positive or
negative

Ideally should be as small
as possible

Not adjustable
Positive scrub radius
Negative scrub radius
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Chassis Specialist: Alignment for Installers
Included Angle

Sum of the camber and SAI angles in a front suspension

Changing camber changes the included angle

Helps diagnose bent suspension parts like spindles and
struts.

Reading is given as degrees and minutes, or degrees and
fractions

Specifications may not be available in all service
information systems
Included Angle
Toe-Out on Turns

Two different paths for each of the steered
wheels (different distances traveled)

Tire squeal at low speeds may be
a symptom of incorrect turning angle

If angle is incorrect, suspect a bent steering
arm
(more than 1.5 degrees difference side to
side)
Toe-out on turns
Set Back

One wheel further back than the other indicates setback

Wheelbase difference side to side indicates setback

Usually no more than ¼″ difference from side to side

May be the cause of incorrect caster (1 degree or more)
Setback of the
front wheels
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Chassis Specialist: Alignment for Installers
Vertical 0°
Caster:

Vertical angle of a wheel’s steering axis from
Negative
Positive
the side

Tilting a steering axis backward is positive
caster, forward is negative caster
Cross Caster Angle:

Caster angles illustrated
The difference between side to side caster
settings

May be set at half a degree difference,
but, more than half a degree difference
may cause a steering pull toward the side
with the most negative (least) caster

Caster on the left front wheel is
sometimes decreased to compensate for
road crown
Cross caster reading on
an alignment printout
What would the reading
on the other side be?
How is caster adjusted?
________________________________________________________________________________
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Chassis Specialist: Alignment for Installers
Camber:

Inward tilt of the wheel (negative camber) and
outward tilt of the wheel (positive camber)

Can cause tire wear if the angle is incorrect
Cross Camber Angle:

The difference between the camber angle of the left
and right wheels

Important for good handling

The vehicle will steer towards the side with the
highest camber angle

Alignment specifications from information sources
often only provide this angle
Camber tire wear. Watch out for
exposed metal pieces!
How is camber adjusted?
__________________________________________________________________________
__________________________________________________________________________
__________________________________________________________________________
__________________________________________________________________________
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Chassis Specialist: Alignment for Installers
Toe:

Measures how much the tire points inward or outward
(compared to the vehicle centre line)
How is toe adjusted?
_____________________

Usually set at or close to zero (parallel)

Difference between the leading and trailing edges of two
_____________________
tires on the same axle
_____________________

Distance comparison between the leading and trailing edges
_____________________
of the tires

Major cause of tire wear, both front and rear
_____________________
_____________________
_____________________
_____________________
_____________________
_____________________
_____________________
______
Toe Out
Toe In
Tire wear from incorrect toe, note the
“feathered edge”
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Chassis Specialist: Alignment for Installers
Preliminary Checks:

Customer concerns (verify)

Service bulletins

Tire pressure/condition/size

Sagging suspension/ride height

Condition of components

Front end inspection
Road Test:
The under inflated tire on this vehicle will
affect the alignment settings.

Steering wheel pulls to the left or right

Feeling of looseness or wandering

Steering wheel vibration or shimmy

Steering wheel is not centered when car is moving straight ahead

“Bump” or “Memory” steering problems
Factors which may be mistaken for alignment problems:

Worn suspension components

Torque steer

Memory steer from seized component

Brake pull

Tire inflation

Power steering problems

Module/sensor input
Sequence of adjustments (general):
1.
Rear camber
2.
Rear toe
3.
Caster/camber on one front side
4.
Caster/camber on the other front side
5.
Front toe
The cargo in this truck may affect
alignment settings
Always check service or
manufacturer
information for exact
instructions!
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Chassis Specialist: Alignment for Installers
Adjusting the Settings
Caster
 Caster may be adjustable
by adding or removing
shims, or by moving a
cam. (see camber, below)
Shims
 Caster may not be
adjustable on all
vehicles.
Camber/Caster
Camber
 SLA suspensions may
use adjuster cams or
shims, as used for caster.
 Strut-type suspensions
may be adjustable by
repositioning the strut or
by using an aftermarket
kit—check service
information.
Toe
 Front toe is adjusted
through the tie rod ends
 Rear toe adjustment
procedures vary
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Chassis Specialist: Alignment for Installers
Common Terms and Definitions
Two-Wheel Alignment: Front wheels are aligned; if the rear wheels are NOT parallel to the vehicle centerline,
the steering wheel may be off-center and the tires may wear unevenly.
Four-Wheel Alignment: All four wheels are measured and taken into account, then adjusted as possible.
Bump Steer: The tendency to suddenly steer to one side after hitting a bump or pothole.
Camber: Inward and outward tilt of a wheel.
Caster: Forward and rearward tilt of the steering axis.
Cross Camber or Cross Caster: The slight side-to-side difference to compensate for road crown.
D-Height: A measurement from the rear suspension components used to determine height
Geometric Centerline: Formed by connecting imaginary lines between the midpoint of the front spindles and
the midpoint of the rear axle. If the vehicle is properly aligned, the wheels roll in a line parallel with the
vehicle’s geometric centerline.
Included Angle: The sum of SAI and camber often used to diagnose bent parts.
Memory Steer: The steering wheel and wheels wanting to return to a position other than the center after turning.
This may cause a pull or drift to one side, usually caused by binding components.
Ride Height: A measurement between the ground and a fixed reference point on a vehicle; may be synonymous
with “ground clearance.”
Road Crown: The slope of the road for proper drainage; excessively crowned roads may cause a vehicle to pull
to the right.
Set Back: When one of the wheels is further back than the other, the vehicle has setback.
Steering Axis Inclination (SAI): The measurement, in degrees, of the steering pivot line when viewed from the
front of the vehicle; not usually adjustable and used to diagnose bent components.
Thrust Angle: The angle between the thrust line and centerline.
Thrustline: A line equally dividing the total rear toe and defining the direction of the rear wheels.
Toe: The angle most likely to wear out tires; the difference between front and rear edges of the tires on the same
axle.
Toe-out on turns: Angles formed by the front wheels when turning; also used to diagnose bent components.
Trim Height: Like “Ride height”, but usually referencing “Z-height” or “D-height.”
Vertical Reference Line: Perfectly vertical, imaginary line used to reference the angle of a component.
Wheelbase: The distance from the center of the front wheels to the center of the rear wheels.
Z-Height: A measurement from the front suspension components to determine height.
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