chap93 pps Automotive technology at University of Cambridge

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Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition
By James D. Halderman

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OBJECTIVES:
After studying Chapter 93, the reader should
be able to:

•
•
•

Prepare for ASE Suspension and Steering (A4) certification
test content area “D” (Wheel Alignment Diagnosis,
Adjustment, and Repair).

List the many checks that should be performed before
aligning a vehicle.
Describe the proper alignment setup procedure.

Continued
Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition
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OBJECTIVES:
After studying Chapter 93, the reader should
be able to:

•
•

•

Explain how to correct for memory steer, torque steer, pull,
drift (lead), and wander.
Describe the use of unit conversion and diagnostic charts.
Discuss tolerance alignment and how to check for accident
damage.

Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition
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KEY TERMS:
Degrees
eccentric cam

five-wheel alignment • four-wheel alignment • fractional
geometric centerline
memory steer • minutes
prealignment checks
ride height
Continued
Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition
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KEY TERMS:
shim chart • spoke angle
thrust line • tolerance adjustment • torque steer • total toe

Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition

By James D. Halderman

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Proper wheel alignment of all four wheels is important for the
safe handling of any vehicle.
When all four wheels are traveling the same path and/or being
kept nearly vertical, tire life and fuel economy are maximized
and vehicle handling is sure and predictable.
A complete wheel alignment is a complex process that includes
many detailed steps and the skill of a highly trained tech.

Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition
By James D. Halderman

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PREALIGNMENT CORRECTION TECHNIQUES
A thorough inspection of the steering, suspension, and tires should
be performed before the alignment of the vehicle is begun.
There are four basic steps in the correction of any problem:
1. Verify What, when, where, and to what extent does the
problem occur?
2. Isolate Eliminate known good parts and systems. Always
start with the simple things first. For example, checking and
correcting tire pressure and rotation of the tires should be one
of the first things performed whenever trying to isolate the
cause of an alignment-related problem.
Continued
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3. Repair the problem This step involves replacing any worn or
damaged components and making sure that the alignment is
within factory specifications.
4. Recheck Always test-drive the vehicle after making a repair.
Never allow the customer to be the first to drive the vehicle after
any service work.

Figure 93–1 The owner of this Honda thought
that all it needed was an alignment. Obviously,
something more serious than an alignment
caused this left rear wheel to angle inward at
the top.

Continued

Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition
By James D. Halderman

Continued
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Align and Replace at the Same Time
Magnetic bubble-type camber/caster gauges can be mounted directly on the hub or on an adapter
attached to the wheel or spindle nut on front-wheel-drive vehicles. Besides an alignment setting
tool, a magnetic alignment head is great tool use when replacing suspension components.

Any time a suspension component is replaced, the wheel alignment should
be checked and corrected as necessary. An easy way to avoid having to
make many adjustments is to use a magnetic alignment head on the front
wheels to check camber with the vehicle hoisted in the air before replacing
front components, such as new MacPherson struts.

Figure 93–2 Magnetic bubble-type
camber/caster gauge. To help it
keep its strong magnetism, it is best
to keep it stored stuck to a metal
plate as shown here.

Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition
By James D. Halderman

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PREALIGNMENT CHECKS
Before checking or adjusting the alignment, these items should be
checked and corrected, as part of the prealignment checks:

1. Check all the tires for proper inflation pressures. Tires should

be approximately the same size and tread depth, and the
recommended size for the vehicle. See Figure 93–3.
NOTE: Some alignment techs think that the vehicle must have new tires
installed before an accurate alignment can be performed. Excessively worn
tires, especially if only one tire is worn, can cause the vehicle to lean
slightly. It is this unequal ride height that is the important fact to consider.
If, for example, all four tires are equally worn, then the vehicle can be
properly aligned. (Obviously, excessively worn tires should be replaced,
and it would be best to align the vehicle with the replacement tiresinstalled
to be assured of an accurate alignment.)
Continued
Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition
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Figure 93–3 Typical tire wear chart as found in a service manual. Abnormal tire wear usually
indicates a fault in a steering or suspension component that should be corrected or replaced
before an alignment is performed.

Continued
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2. Check the wheel bearings for proper adjustment.
3. Check for loose ball joints or torn ball joint boots.
4. Check the tie rod ends for damage or looseness.
5. Check the center link or rack bushings for play.
6. Check the pitman arm for any movement.
7. Check for runout of the wheels and the tires.

NOTE: Manufacturers often have replacement springs or spring spacers
that can be installed between the coil spring and the spring seat to restore
proper ride level.
Continued
Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition
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8. Check for vehicle ride height (should be level front to back as
well as side-to-side). Make sure that the factory load-leveling
system is functioning correctly, if the vehicle is so equipped.
Check height according to the manufacturer’s specifications.

Figure 93–4 Measuring points for ride (trim) height vary by manufacturer. (Courtesy of Hunter
Engineering Company)

See Figure 93-5.
Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition
By James D. Halderman

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Figure 93–5 Measuring to be sure the left and right sides of the vehicle are of equal height. If this
measurement is not equal side-to-side by as little as 1/8 in. (3 mm), it can affect the handling of the
vehicle.

Continued
Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition
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9.

Check for steering gear looseness at the frame.

10. Check for improperly operating shock absorbers.
11. Check for worn control arm bushings.
12. Check for loose or missing stabilizer bar attachments.
13. Check the trunk for excess loads.
14. Check for dragging brakes.
NOTE: Checking for dragging brakes is usually performed when
installing alignment heads to the wheels prior to taking an alignment
reading. A brake dragging can cause the vehicle to pull or lead toward the
side with the dragging brake.
Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition

By James D. Halderman

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LEAD/PULL
Diagnosis Many alignment requests come from attempts to have a
lead or pull condition corrected. Before aligning the vehicle, verify
the customer complaint first, then perform a careful inspection.

1. Inspect all tires for proper inflation. Both tires on the same axle
(front and rear) should be the same size and brand. A lead/pull
problem could mean a defect or condition in one or more tires.
Figure 93–6 The bulge in this tire was not noticed until it
was removed from the vehicle as part of a routine brake
inspection. After replacing this tire, the vehicle stopped
pulling and vibrating.

Before attempting to correct a
lead/pull condition by changing
alignment angles, try rotating
tires front to back or side to side.
Continued
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2. Road test the vehicle on a straight, level road away from traffic,
if possible. Bring the vehicle to about 40 mph (65 km/h), shift
into neutral, and feel for a pull in the steering, either to the left
or to the right. A lead or drift is less severe than a pull, and may
occur only if you momentarily remove your hands from the

steering wheel while driving.
3. If the lead/pull problem is sometimes toward the left and other
times toward the right, check for a memory steer condition.
If the lead/pull problem occurs during acceleration and
deceleration, check for a torque steer condition.

Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition
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MEMORY STEER
Diagnosis Memory steer is a term used to describe the lead or pull
of a vehicle caused by faults in the steering or suspension system.
Often a defective upper strut bearing or steering gear can cause a
pulling condition in one direction after making a turn, as if the

vehicle had a memory and pulled the same direction
Correction A binding suspension or steering component is the
most likely cause of memory steer. Disconnect each wheel from its
tie rod end and check for free rotation of movement of each wheel.
Each front wheel should rotate easily without bind or roughness.
Repair or replace components as necessary to eliminate the binding
condition.
Continued
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NOTE: One common cause of memory steer is the installation of steering
or suspension components while the front wheels are turned. Most steering
and suspension parts contain rubber, which has a memory if moved from

its installed position. If the memory steer condition is only in one direction,
then this is the most likely cause. The rubber component exerts a force on
the suspension or steering that causes the vehicle to pull toward the side
that the wheels were turned toward when the part was installed.
To test for memory steer, follow these steps during a test drive:

1. With the vehicle stopped at an intersection or in a parking
area, turn the steering wheel completely to the left stop and
then straighten the wheel without going past the straightahead position.
2. Lightly accelerate the vehicle and note any tendency of the
vehicle to lead or pull toward the left.
3. Repeat the procedure, turning the steering wheel to the right.
Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition
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The Five-Wheel Alignment
The steering wheel should always be straight when driving on a straight, level
road. If the steering wheel is not straight, the customer will often think that the
wheel alignment is not correct.
One such customer complained that the vehicle pulled to the right while
driving on a straight road. The service manager test drove the vehicle and
everything was perfect, except that the steering wheel was not perfectly
straight, even though the toe setting was correct. Whenever driving on a
straight road, the customer would “straighten the steering wheel” and, of
course, the vehicle went to one side.
After adjusting toe with the steering wheel straight, the customer and the
service manager were both satisfied. The tech learned that regardless of
how accurate the alignment, the steering wheel must be straight; it the
“fifth wheel” that the customer notice most.
A five-wheel alignment includes a check of the steering wheel.
Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition
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NOTE: Many vehicle manufactures now include the maximum allowable
steering wheel angle variation from straight. This specification is
commonly ±3 degrees (plus or minus 3 degrees) or less.

Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition
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TORQUE STEER
Diagnosis Torque steer occurs in front-wheel-drive vehicles when

engine torque causes a front wheel to change its angle
from straight ahead.
This pulling effect is most noticeable during rapid acceleration,
especially when upshifting of the transmission creates a sudden
change in torque being applied to the front wheels.
When turning and accelerating at the same time, torque steer has a
tendency to straighten the vehicle, so more effort may be required
to make the turn. If the accelerator is released, a reversing force is
applied to the front wheels.
See Figure 93–7.
Continued
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Figure 93–7 Equal outer CV joint angles produce equal steer torque (toe-in). If one side
receives more engine torque, that side creates more toe-in and the result is a pull toward one
side, especially during acceleration.

Continued
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Most manufacturers try to reduce torque steer in the design of their
vehicles by keeping drive axle angles low and equal side-to-side. If
the engine and transaxle are level and the drive axle shafts are kept
level, then the torque from the engine will be divided equally.
Correction The service technician cannot change the design of a
vehicle, but the technician can, and should, check and correct

problems that often cause torque steer. Check to be sure the
condition is not normal.
It is normal for front-wheel-drive vehicles to exert a tug on the
steering wheel and steer toward one side (usually the right) during
acceleration. This is especially noticeable when the transmission
shifts from first to second gear under heavy acceleration.
Continued
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To determine how severe the problem is, place a strip of masking
tape at the top of the steering wheel.
Drive the vehicle and observe the amount of movement required
to steer the vehicle straight during heavy acceleration.

Repeat the test with a vehicle of similar make and model.
If the torque steer is excessive, determine and correct the cause
by carefully following the prealignment inspection steps and
checking for a level power train.
A defective engine mount can cause the entire drive train to sag
on one end. If the engine and transaxle of any front-wheel-drive
vehicle is not level, the drive axle shaft angles will not be equal.
Continued
Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition
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