TÀI LIỆU OTO BẰNG TIẾNG ANH VỀ ECS and wheel aligment_HMC

CONTENTS WHEEL ALIGNMENT NECESSITY OF WHEEL ALIGNMENT ---WHAT HAPPENS DURING AN ALIGNMENT ---EQUIPMENT REQUIREMENTS ---HEIGHT MUST BE RIGHT ---DIAGNOSIS PROCEDURE FOR ALIGNMENT ---C

WHEEL ALIGNMENT

& ECS

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CONTENTS WHEEL ALIGNMENT

NECESSITY OF WHEEL ALIGNMENT

-WHAT HAPPENS DURING AN ALIGNMENT

-EQUIPMENT REQUIREMENTS

-HEIGHT MUST BE RIGHT

-DIAGNOSIS PROCEDURE FOR ALIGNMENT

-CAMBER

-CASTER

-TOE

-STEERING AXIS INCLINATION (SAI)

-INCLUDED ANGLE

-STEERING OFFSET

-SET BACK

-THRUST ANGLE

-STEERING CENTER

-TOE OUT ON TURNS

-DIAGNOSIS BY VEHICLE SYMPTOM

-INTEGRATED FRAME AND BODY (MONOCOQUE)

-SUSPENSION SYSTEMS

-FRONT SUSPENSION

-REAR SUSPENSION

-SPRUNG WEIGHT AND UN -SPRUNG WEIGHT

-SIMPLIFIED SUSPENSION MODEL

OSCILLATION OF SPRUNG WEIGHT

-SEMI-ACTIVE ECS

SEMI-ACTIVE ECS (Electronic Controlled Suspension)

-SKY HOOK SYSTEM

-SKY HOOK DAMPER - ADVANTAGE OF REVERSE TYPE DAMPER

-SYSTEM PERFORMANCE

-CONSTRUCTION AND OPERATION OF SHOCK ABSORBER

-ECS SHOCK ABSORBER

-DAMPING FORCE CHARACTERISTICS

-SEMI-ACTIVE CONTROL

-CONSTRUCTION OF SEMI-ACTIVE ECS

-INPUTS & OUTPUTS

-INPUTS 1) ALTERNATOR 'L' TERMINAL

-2) BRAKE SWITCH

-3) ECS MODE SWITCH (SPORT/NORMAL SWITCH)

-4) VEHICLE SPEED SENSOR

-5) STEERING SENSOR

-6) THROTTLE POSITION SENSOR

-7) ACCELERATION SENSOR (G-SENSOR)

-OUTPUTS 1) ACTUATOR RELAY

-2) ECS LAMP

-3) SOLENOID VALVE (PROPORTIONAL TYPE)

-DTC LIST

-DIAGNOSTIC TROUBLE CODE

-WIRING DIAGRAM

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WHEEL ALIGNMENT

NECESSITY OF WHEEL ALIGNMENT

Wheel alignment is just adjusting the relationship between the suspension and steeringcomponents, the wheels, and the frame of the vehicle Vehicle manufacturers determine whichangles are adjustable from the factory based on need and feasibility Various adjustmentmechanisms such as shims, cams, threaded rods and slotted frames usually provide enoughadjustment, providing height is correct, to bring the vehicle into specification When the angles areall as specified, the car or truck is properly aligned, and the best possible compromise has beenachieved among minimum rolling friction, maximum tire mileage, stability of the car on the road,and steering control for the driver Vehicle accident, road shock and general wear and tear canmake some of these angles out of spec When that happens, control of the vehicle may bethreatened, and the tires may begin to wear unevenly and rapidly The car needs to be realigned tohave all the proper angles restored

The warning signs suggesting the need for alignment are:

- Irregular wear on tires Look closely at all four of your tires If one or more of themdemonstrate excessive wear on one side, or wear in a cupped, scalloped or diagonal stripepattern at edges or across the tread, or uneven wear but with "feathered" edges on thetreads, an alignment could be needed

- Unusual steering feeling If the steering feels stiffer than it used to, or if the wheel does notreturn to the center position when released, or if the car feels skittish the wheels may be out

be set properly for the alignment to be correct

- Four-wheel alignment is essential on vehicles with front wheel drive (FWD) and independentrear suspension The rear wheels should follow the fronts in a parallel path If the rear wheelsare pointed in a slightly different direction, they affect tire wear and the vehicle's stability

Common alignment errors to avoid are:

- Failing to perform an accurate vehicle inspection, including height measurement, to assure

a quality alignment

- Failing to pull the rear turn-plate pins during a thrust alignment

- Overtorquing rear hub attachment bolts, causing possible full or partial contact shim

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deformation

- Remembering to inspect the vehicle for the presence of a rear shim prior to cutting a newone

Other facts should be known about wheel alignments:

- A wheel alignment should always start and end with a test drive

- The front end and steering linkage should be checked for wear before performing analignment

- The tires should all be in good shape with even wear patterns

- Pulling problems are not always related to wheel alignment, problems with tires, brakes andpower steering can also be responsible It is up to a good wheel alignment technician todetermine the cause

WHAT HAPPENS DURING AN ALIGNMENT

Before a wheel alignment, a thorough inspection of the entire undercar, including suspension parts,bushings, steering linkage, ball joints and wheel bearings, wheels and tires as well as the vehicle'sframe and ride height Loosened or bent parts need to be checked Once this inspection iscomplete, the car will be checked and adjusted on the alignment machine in order, camber, casterand toe, beginning with the rear wheels

Items to be checked before the measurement of wheel alignment are :

- Tire inflation pressure (under standard condition)

- Uneven wear of tires or difference in tire sizes

- Ball joint play due to wear

- Tie rod end play due to wear

- Front wheel bearing play due to wear

- Lengths of left and right strut bars

- Deformation or wear of steering linkage parts

- Deformation or wear of parts related to front suspension

- Chassis-to-ground clearance

Alignment checks are recommended whenever steering, suspension parts, or some front-wheeldrive (FWD) driveline components are replaced, or when new tires are installed, or whencustomers complain of vehicle pulling or abnormal tire wear such as scuffing, cupping or moreaccelerated wear on one side of the tire

The type of alignment performed usually is conditional upon the amount of adjustment that'sfeasible on a particular vehicle, as well as the shop's equipment capability On solid-axle, rear-wheel-drive (RWD) vehicles, for example, a thrust alignment is usually performed so the frontwheels are aligned to the rear axle The drive direction of the rear axle is referred to as the thrustline, which should in theory be the same as the geometric center of the vehicle

A four-wheel alignment involves adjusting the rear wheels to achieve proper camber and toe and athrust angle as close to zero as possible, then adjusting the front wheels to the same vehiclecenterline Four-wheel alignments are recommended for most FWD cars, MPV(Multi PurposeVehicles), some SUV(Sport Utility Vehicles) and RWD vehicles with independent suspension

EQUIPMENT REQUIREMENTS

To perform a four-wheel alignment, a four-sensor machine is required Turnplates or rear slipplates at all four corners are needed during both four-wheel and thrust alignments The rearwheels must be allowed to relax to their normal position to achieve proper readings whether theyare to be adjusted or not

In addition to providing caster, camber and toe readings, alignment machines can be used as adiagnostic tool Diagnostic angles such as Steering Axis Inclination (SAI), Included Angle (IA),Setback and Turning Radius can help the technician to identify problems that otherwise might beoverlooked When the SAI reading is combined with the camber reading, the sum of the twoangles equals the IA Using SAI/IA and camber will help identify a bent or shifted component Theoptimum setting on all vehicles for Setback is zero, so either a positive or negative Setbackreading indicates cradle shifting or some other component has moved

Turning Radius, also referred to as toe-out on turns, is determined by the steering arms relative tothe lower steering pivot When the vehicle is steered into a turn, the steering arms cause thewheels to turn at different angles, creating a toe-out condition If the turning radius is incorrect,

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Thrust line

Geometric

center line

inspect the steering arm and lower steering pivot components for damage Using the turnplates onalignment equipment, a technician can check for a bent steering arm by measuring the amount oftoe-out on turns for each wheel and compare them

HEIGHT MUST BE RIGHT

Some of today's alignment equipment also can diagnose ride height, which is critical to properalignment and suspension geometry Ride height is the angle that all wheel alignment angles arebuilt around and should be kept within manufacturer specifications for optimum performance of theentire steering, suspension and driveline system

When vehicles have been modified from the manufacturer's original design, factory alignmentsettings may no longer apply Altering tire sizes may upset the spindle's distance from the ground,which can have an effect on scrub radius Raising or lowering vehicle height may alter thesuspension and steering systems' geometry during deflection and cause excessive toe change orstress some parts beyond their limits

Weak, sagging springs can force the entire steering and

suspension system to go out of proper alignment, which spells

problems for any vehicle A correct alignment with a sagged

suspension can still produce tire wear and handling problems

during dynamic operation The best way to fix the ride height is

to replace the springs (Note: springs should only be replaced

in matched pairs) Changes in riding height will affect camber

and toe so if springs are replaced or torsion bars are adjusted,

then the wheel alignment must be checked to avoid the

possibility of tire wear It is important to note that the only

symptom of weak coil springs is a sag in the riding height If

the riding height is good, then the springs are good

Air suspended vehicles may have a specified procedure that is necessary to achieve the correctalignment height prior to adjustment On some air suspension systems, it is first necessary toallow the air in the air spring to reach shop temperature prior to alignment

Failure to detect incorrect chassis height can often lead a technician to a wrong diagnosis, such

as attributing the lack of adjustment range to a bent frame

DIAGNOSIS PROCEDURE FOR ALIGNMENT

[Camber change by

a sagging spring]

Tire, brake and driveline problems are often mistaken for an alignment problem by the vehicleowner, so the customer should be consulted as to what made them think the vehicle needsaligning Begin by asking the customer a few simple questions, such as: What is your vehicledoing to make you think you need an alignment? Does it pull? When does it pull? Is the steeringwheel straight? Are the tires worn unevenly?

Next, verify the problem with a test drive and a complete inspection of the tires and the wearpatterns they display that indicate a steering or suspension problem If the customer is getting newtires, examine the old ones for unusual wear before they come off the vehicle Explain to thecustomer how new tires will experience the same wear as the old ones unless the underlyingcause of the problem is corrected

If a loose steering or suspension part is discovered, show the customer the actual problem Ifpossible, demonstrate a properly functioning part on a similar vehicle in the shop for comparison.Due to the hectic schedule in most shops, this step is sometimes overlooked even though peoplelearn best from hands-on experience

It's essential to always be precise when discussing factory specifications for steering andsuspension components Some chassis parts must exceed a listed tolerance for looseness toactually require replacement In many cases, the part can be within its tolerance range but stillcontribute to tire wear, alignment and handling problems Some amount of looseness within thisspec could create problems for the driver of the vehicle, but the replacement is not required untilthe tolerance is reached When making a service suggestion to the customer, explain thatalthough the ball joint may be within its listed tolerance, the looseness could allow wheelmovement and create alignment angle changes A part that is loose, but still within its listedtolerance, should never be described as bad

Some steering components such as tie rod ends may not have a listed tolerance Inspection ofthese components may rely entirely on the technician's judgment, using hand pressure or someother approved method as a measure of excessive looseness

CAMBER

Camber is the angle of the wheel, measured in degrees, when

viewed from the front of the vehicle The front wheels of the

car are installed with their tops tilted outward or inward This is

called camber and is measured in degrees of tilt from the

vertical When the top of a wheel is tilted outward, it is called

positive camber Conversely, inward inclination is called

negative camber

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On many vehicles, camber changes with different road

speeds This is because aerodynamic forces cause a change

in riding height from the height of a vehicle at rest Because of

this, riding height should be checked and problems corrected

before setting camber For many years the trend has been to

set the camber from zero to slightly positive to offset vehicle

loading, however the current trend is to slightly negative

settings to increase vehicle stability and improve handling

If the camber is out of adjustment, it will cause tire wear on

one side of the tire's tread If the camber is too far negative, for

instance, then the tire will wear on the inside of the tread On

many front-wheel-drive vehicles, camber is not adjustable If

the camber is out on these cars, it indicates that something is

worn or bent, possibly from an accident and must be repaired

or replaced

Positive Camber

Slight positive camber results in a dynamic loading that allows

the tire to run relatively flat against the road surface Positive

camber also directs the weight and shock load of the vehicle

on the larger inner wheel bearing and inboard portion of the

spindle rather than the outboard bearing Positive camber in

moderation results in longer bearing life, less likely sudden

load failure, and as a side benefit, easier steering Excessive

positive camber wears the outside of the tire and can cause

wear to suspension parts such as wheel bearings and

spindles

Giving the wheel positive camber causes the load to be

applied to the inner side of the spindle, reducing the force

acting on the spindle and the steering knuckle

The reactive force, which is equal in size to the vehicle load, is

applied to the wheel perpendicularly to the road this is divided

into perpendicular force to the axis of the spindle and parallel

force to the axis of the spindle which forces the wheel inward,

helping to prevent the wheel from slipping off the spindle The

inner wheel bearing is made larger than the outer one in order

to bear this load

[Camber wear pattern]

[Vehicle load & Wheel bearing]

Vehicle load

Inner wheel bearing

Vehicle load

Outer wheel bearing

Negative Camber

Variations in negative camber can be used to improve the

handling of a vehicle A setting of 1/2° negative on both sides

will improve cornering without affecting tire life greatly This

negative setting compensates for the slight positive camber

change of the outside tire due to vehicle roll, thereby allowing a

flatter tire contact patch during cornering Excessive negative

camber wears the inside of the tire and similar to positive

camber, it can cause wear and stress on suspension parts

Rear Camber

Rear camber is not adjustable on most rear wheel drive vehicles These vehicles are built with zerocamber setting and are strong enough not to flex or bend under normal load Most front wheel drivevehicles have a manufacturers specification calling for a slight amount of rear camber, usually asmall amount of negative camber for cornering stability If the manufacturers specification allows, asetting of 0° to -0.5°(30’) is preferred for tire wear and ride stability If rear camber settings change,defected rear suspension parts are necessarily replaced However, most vehicles can be adjusted

by using an aftermarket type of adjustment, such as shims, cam bolts or bushings

Road Crown and Camber

A crowned road means that the outside/right hand side of the lane is lower than the left side of thelane This improves the drainage of the road but adversely affects vehicle handling Road crownmust be compensated for in alignment settings because a vehicle driving on a crowned road leans

to the right, causing some weight transfer to the right, and the camber changes slightly morepositive This combination creates a pull or drift to the right Most alignment technicians adjust thevehicle with a slightly more positive camber, usually 1/4°(15’), on the left to compensate for theroad crown This slightly more positive camber will not cause a noticeable pull when driving on aflat road However, if camber is unequal from side to side with a difference greater than 1/2°(30’),the vehicle will pull to the side with the most positive camber If the specifications allow, 0° to

±0.5°(30’) is usually best for tire life and vehicle handling

Causes of Camber Changes

- Ride height

Always check a ride height specification prior to

beginning alignment Changes in ride height from

specifications affect camber

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[Misaligned Camber]

Pulling to the right

- Sagging of spring

As a vehicle ages, the suspension has a tendency

to sag Excessive vehicle weight or abuse can

cause springs to weaken

- Sagging of cross-member or sub-frame

Another factor to consider is sagging of

cross-member or sub-frame Modifications to the vehicle

such as raising or lowering the suspension or

changing the total weight of the vehicle can also

affect camber

Problems Caused by Incorrect Camber

- Vehicle pulls to one side

- Rapid wear on inside or outside of tire tread

- Increased wear on the wheel bearings

- Increased wear on ball joints (incorrect camber creates

increased leverage on spindle and spindle support

resulting in increased loads on ball joints)

CASTER

Caster can be defined as the forward or rearward tilt of the steering knuckle pivot points, is alsocalled the steering axis Caster is measured in degrees, from the steering axis to true vertical, asviewed from the side On strut equipped vehicles, the line extends through the lower ball joint to thecenter of the upper strut mount

The caster angle is formed by the steering axis and a true vertical line passing through the spindle.The purpose of caster angle is to provide directional control stability for the front wheels to travel astraight course with minimal effort Proper caster angle also helps to return the front wheels to astraight ahead position after a turn Caster has little affect on tire wear

Purpose of Caster are :

- To aid in the directional control of the vehicle by helping the front wheels maintain a straightahead position

- To help return the front wheels to straight ahead position after a turn

- To offset the effects of road crown on vehicle direction

- To operate in concert with the vehicle suspension design, camber angle and steering axisinclination angle to provide the desired camber change during vehicle turns

Many front-wheel-drive vehicles, caster is not adjustable If the caster is out spec, it indicates thatsomething is worn or bent, possibly from an accident, and must be repaired or replaced

Positive caster

Positive caster is when the top of the steering axis it tilted

rearward The caster line intersects the ground ahead of the

contact patch of the tire, which provides good directional control

However, excessive positive caster can cause two problems

The first is that excessive caster will cause a high level of road

shock to be transmitted to the driver when the vehicle hits a

bump and it causes hard steering

The second problem is that a tire with positive caster has a

tendency to toe inward when the vehicle is being driven If one

side has more positive caster than the other, this causes it to

toe inward with more force than the other side This will cause

a lead or pull to the side with least amount of positive caster

Negative caster

Negative caster is when the top of the steering axis

is tilted forward This places the point contact ahead of

the point of load, which provides easier steering at

slower speeds

However, it can cause difficulty in returning out of a

turn and wandering & weaving at high speeds and

is affected by any road surface variation such as

small road irregularities or bumps If the caster is

too negative, the steering will be light and the

vehicle will wander and be difficult to keep in a

Zero caster

Zero caster is when the top of the steering axis is

exactly vertical If the vehicle has unequal caster,

the vehicle pulls to the side with the least positive caster

A maximum side to side variation of ± 0.5°(30’) is

recommended on most vehicles

Movement of spindle while turning

With positive caster, the spindle of inner wheel

moves down and the spindle of outer wheel moves

up while turning

However, it causes the spindle to rise and fall as

the wheels are turned in one direction or the other

Because the tire cannot be forced into the ground

as the spindle travels in an arc, the tire/wheel

assembly raises the suspension

That is why steering effort increases when the

positive caster goes up

TOE

The toe measurement is the difference in the distance between the front of the tires and the back ofthe tires Toe-in, or positive toe, is defined as the front of the tires being closer together than therear of the tires Toe-out, or negative toe, is when the rear of the tires are closer together than thefront of the tires Zero toe is when the tires are parallel to each other

Since most alignment specifications show toe as

total toe of both wheels, it is important to

understand that 1/2 of the total toe should be

applied to each front wheel A minus (-) indicates a

toe-out and toe-in is shown as a positive (+)

Toe-in : B > A, Toe-out : B < A

It is important to note that although toe has

historically been measured as a distance in

Forward

[Positive Caster]

[Spindle movement while turning]

milliliters or decimal inches (B-A), it is becoming

more common to express toe in degrees (α,β) The

idea is that the angle, rather than an arbitrary

distance, determines the side slip of the tire This

should not be affected by the tire size, but rather

should be constant for a given measurement

Ex) Toe-in (B-A) mm(in.) : 0±2mm (0±0.08 in.) or 0.09°± 0.09° (each of α,β)

Role of Toe angle

The main function of toe angle is to cancel out the camber thrust generated when camber isapplied When the front wheels are given positive camber, they tilt outward at the top This causesthem to attempt to roll outward as the car moves forward, and therefore to side-slip This subjectsthe tires to wear Therefore, toe-in is provided for the front wheels to prevent this by cancelingoutward rolling due to camber Since camber approaches zero in most recent vehicles, the toeangle value is also becoming smaller

Suspension rigidity and Toe angle

During driving, forces from various direction are brought to bear on the suspension, with the resultthat the wheels tend to toe out In order to prevent this, some vehicles are given a slight toe-in evenwhen the camber is zero

Effects of Toe

Excessive toe increases tire scuffing and results in tire wear and drag on the vehicle Excessivetoe-in, or positive toe, increases scuffing on the outside of the tire Excessive toe-out, or negativetoe, increases scuffing on the inside of the tire, and in some cases can cause a darting orwandering problem

Early indication of toe tire wear can appear as a feather edge

or scuff on the edge of the tire tread surface Toe tire wear can

also be found on rear tires as a cupping, feather edge or

smooth edge on the tire tread surface Too much toe in will

cause the feather edge to point in while toe out will cause the

feather edge to point out Toe is adjusted by turning the tie rod

Toe adjustment

a Front Toe adjustment

To adjust front toe-in, change the lengths of the tie rod connecting the steering knuckle

- Increasing the tie rod length : increases toe-in

b Rear Toe adjustment

Rear wheel alignment of an independent rear

suspension is accomplished by adjusting the camber

and toe angle The method of adjusting the camber

and toe angle differs depending on the type of

suspension Some models have no mechanism for

adjusting the camber

By turning the eccentric cam, the arm can be moved to

the left or right to change the direction of the wheel,

thus adjusting the toe-in

As with front toe-in, if the length of the rear arms are

not made the same in order to adjust the toe-in of the

rear wheels separately, the angles of the left and right

wheels will differ no matter how correct the toe-in is

For this reason, first of all, correct the angles of the left

and right wheels, then adjust the toe-in

[Correct adjustment]

STEERING AXIS INCLINATION (SAI)

The axis around which the wheel rotates as it turns to the right

or left, is called the steering axis Steering Axis is an imaginary

line through the upper and lower ball joints (pivot joints) on

short & long arm suspensions (ex Double Wishbone type

suspension) This axis is found by drawing an imaginary line

between the top of the shock absorber’s upper support

bearing and the lower suspension arm ball joint (in the case of

strut type suspensions)

Steering Axis Inclination (SAI) is the angle between the

centerline of the steering axis and vertical line from center

contact area of the tire (as viewed from the front) SAI is also

referred to as KPI (King Pin Inclination) on trucks and old cars

with king pins instead of ball joints

Steering offset, or Kingpin offset is the distance between the

wheel center and the point at which the steering axis intersects

the road surface It is negative when the point of intersection is

between the center and the outside of the wheel

SAI provides good driving and handling characteristics through

directional stability and weight projection Directional Stability

is the tendency of a wheel to straighten from a turned position

and remain straight

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Steering offsetSAI

[SAI of MacPherson Strut type suspension]

[SAI of Double Wishbone type suspension]

Since the wheel turns to the right and left with the steering axis

as its center and the offset as the radius, a large offset will

generate a great moment around the steering axis due to the

rolling resistance of the tire, thus increasing steering effort

If the offset is too large, the reactive forces acting on the

wheels during driving of braking, will generate a moment

around the relevant steering axis, causing the wheel to pull to

the side pull especially at very slow speeds This moment is

proportional to the size of the offset As the offset approaches

zero, less moment is generated around the steering axis when

a force is applied to the wheel, and the steering is less

influenced by braking or road shock

Thus, since it has a tendency to maintain or seek a straight ahead position, less positive caster isneeded to maintain directional stability A vehicle provides stable handling without any defects ofhigh positive caster because of SAI

SAI/Camber/IA Troubleshooting Charts (MacPherson Strut type suspension)

Equal to Specs More than Specs More than Specs Bent Spindle and/or Strut Body

More than Specs More than Specs More than Specs Strut Tower IN at Top and Spindle or

Strut BentLess than Specs More than Specs Equal to Specs Bent Control Arm or Strut OUT at Top

and Bent Spindle or Bent Strut BodyLess than Specs More than Specs Less than Specs Bent Control Arm or Strut OUT at Top

and Bent Spindle or Strut BodyLess than Specs More than Specs More than Specs Bent Control Arm or Strut OUT at Top

and Bent Spindle or Strut BodyEqual to Specs Less than Specs Less than Specs Bent Spindle and/or Bent Strut Body

Less than Specs Less than Specs Less than Specs Strut Top or Bent Control Arm and

Bent Spindle or Strut BodyMore than Specs Less than Specs Equal to Specs Strut Tower IN at Top

SAI/Camber/IA Troubleshooting Charts (Double Wishbone type suspension)

SAI Camber Included Angle Problem Area

More than Specs Equal to Specs Less than Specs Spindle/Knuckle or Upper Control

Arm and/or Control Arm MountLess than Specs Equal to Specs More than Specs Bent Lower Control Arm and/or

Lower Control Arm MountEqual to Specs More than Specs More than Specs Spindle/Knuckle Assembly

Less than Specs More than Specs Equal to Specs Bent Lower Control Arm

Less than Specs More than Specs More than Specs Spindle/Knuckle Assembly

Bent Lower Control Arm Equal to Specs Less than Specs Less than Specs Spindle/Knuckle Assembly

More than Specs Less than Specs Equal to Specs Bent Upper Control Arm

Measuring Procedures

SAI should always be measured after you have adjusted the camber and caster to the properspecifications or as close to the specifications as possible Check for worn suspension parts SAI isbest measured with the front wheels off the ground, brakes applied and alignment equipmentleveled and locked Raise the vehicle underneath the lower control arms but do not relax thesuspension Not raising the vehicle from the turntables can cause the control arm bushings tomove when wheels are turned, resulting in an inaccurate reading

However SAI is typically not adjustable The most likely cause for SAI being out is bent parts whichmust be replaced to correct the condition A maximum variation side-to-side of ± 1.0° may alsoindicate vehicle damage

INCLUDED ANGLE

Included angle is not directly measurable It is the combination of

SAI and camber Viewed from the front, the included angle is SAI

plus camber if the camber is positive (Included angle will be

greater than the SAI) If the camber is negative the included angle

is SAI minus camber (Included angle will be less than the SAI)

The included angle must be the same from side to side even if the

camber is different If a side-to-side variation greater than ± 1.5°

exists, then something is bent, most likely the steering knuckle

SAI + Camber = Included Angle (I/A)

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STEERING OFFSET

Steering offset, or Kingpin offset is the distance at the road

surface between the tire line and the SAI line extended downward

through the steering axis The line through the steering axis

creates a pivot point around which the tire turns Therefore this

distance must be exactly the same from side to side otherwise the

vehicle will pull strongly at all speeds

Positive steering offset is when the tire contact patch is outside of

the SAI pivot, while negative steering offset is when the contact

patch is inboard of the SAI pivot (front wheel drive vehicles usually

have negative steering offset)

The greater the steering offset (positive or negative), the greater the steering effort and the moreroad shock and pivot binding that takes place When the vehicle has been modified with offsetwheels, larger tires, deflated tires, height adjustments and side to side camber differences, thesteering offset will be changed and the handling and stability of the vehicle will be affected

Steering offset is designed at the factory and is not adjustable If you have a vehicle that is pullingeven though the alignment is correct, look for something that will affect steering offset

SET BACK

Front set back is when one front wheel is set further back

than the other wheel And rear set back is when one rear

wheel is set further back than the other wheel Excessive

set-back is normally created by frame or chassis errors

These errors are brought about in most cases by front

end collision and in some cases by a manufacturing

tolerance error If the frame is adjusted incorrectly, or

damage is present, it is not unusual to also see a

reduced positive caster reading on the side with the

setback condition

Rear setback may be caused from frame, chassis, and rear chassis mis-alignment due to collision

If the vehicle has a setback condition, the vehicle may pull to the opposite side of the setback.Excessive setback can cause an alignment pull to the side with the setback If the rear axle ispositioned correctly and all other parts and systems of the vehicle are in good working order, asetback condition will also create different wheelbase measurement side to side

Steering offset (+)

Set Back

It is therefore the most accurate reference when measuring or adjusting the front wheels.

Inspection of the tires can help in diagnosing some wheel alignment failures The tire wear patternsassociated with improper alignment include single shoulder wear, cupping and feather edging

STEERING CENTER

Steering center is simply the fact that the steering wheel is

centered when the vehicle is traveling down a straight and

level road When setting steering center, the rear toe

should be set first bringing the thrust angle as close to the

vehicle centerline as possible Then the steering wheel is

locked in a straight ahead position while the front toe is

set Before locking the steering wheel, the engine should

be started and the wheel should be turned right and left a

couple of times to take any stress off the power steering

valve Of course, you should always road test the vehicle

after every alignment as a quality control check

Chonan Technical Service Training Center21

Centerline

Thrust lineThrust

Angle

[ Positive Thrust Angle]

[ Steering center]

TOE OUT ON TURNS

If the right and left steering angles

were the same, they would have the

same turning radius (r1 = r 2), but

each wheel would turn around a

different center, (O1 and O2)

Smooth turning would therefore be

impossible due to side-slipping of

the tires The result is that, even

though the air pressure in each of

the tires might be equal, and even

though the other wheel alignment

factors might be correct, the tires

would undergo unusual wear

For this reason, the inside front

wheel must steer at a sharper angle

than the outside wheel This is also

known as the Ackerman effect In an

actual vehicle, Toe Out On Turns is

accomplished by the steering

linkage is modified in such a way

that the proper steering angles of the

left and right front wheels are

attained, to achieve the desired

turning radii The steering arm is

either part of the steering knuckle or

[At same turning radius (α=β)]

[At different turning radius (α<β)]

part of the ball joint and is not

adjustable

To check toe out on turns, make sure that the readings are at zero on each side when the wheelsare straight ahead and then steer the wheels to the left so that the inner wheel is at 20°, the outwheel should be less than 20°, optimal reading is 18° Repeat the test in the other direction, If there

is a problem with the toe-out, it is due to a bent steering arm that must be replaced

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DIAGNOSIS BY VEHICLE SYMPTOM

Vehicle

Vehicle

Excessive wheel/rim runout Worn or defective shocks/struts.

Power steering reaction bracket loose Tires out of balance.

Steering gear box (rack) mount loose Incorrect wheel alignment.

Steering gear adjustment loose Incorrect tire inflation.

Tires out of balance Brakes dragging.

Tires out of round Mismatched tires or Radial Pull.

Wheel bearings worn or loose Frame bent.

Worn steering/suspension components Control arm bushing worn.

Ball joint tight or seized Power steering valve not centered Bent steering knuckle or supports Broken or sagging springs.

Damaged suspension components Uneven sway bar links.

Front tire pressure low Incorrect wheel alignment.

Idler arm bushing too tight Incorrect tire inflation.

Power steering fluid low or belt loose Wrong tires for vehicle.

Power steering pump defective Worn shock/strut.

Steering gear out of adjustment Improper vehicle height.

Incorrect wheel alignment. Rack & Pinion or steering not positioned

Premature

Tire Wear

Pulls To One Side

Vehicle Wandering

Front End

Shimmy

Hard

Steering

INTEGRATED FRAME AND BODY (MONOCOQUE)

The integrated frame and body type of construction also referred to as unitized construction,combines the frame and body into a single, one-piece structure This is done by welding thecomponents together, by forming or casting the entire structure as one piece, or by a combination

of these techniques Simply by welding a body to a conventional frame, however, does notconstitute an integral frame and body construction In a truly integrated structure, the entire frame-body unit is treated as a load-carrying member that reacts to all loads experienced by the vehicle-road loads as well as cargo loads

[Integrated frame and body]

Integrated-type bodies for wheeled vehicles are fabricated by welding preformed metal panelstogether The panels are preformed in various load-bearing shapes that are located and oriented so

as to result in a uniformly stressed structure Some portions of the integrated structure resembleframe-like components, while other resembles body-like panels This is not surprising, because thestructure must perform the functions of both of these elements

An integrated frame and body type construction allows an increase in the amount of noisetransmitted into the passenger compartment of the vehicle However, this disadvantage is negated

by the following advantages:

- Substantial weight reduction, which is possible when using a well-designed unitized body

- Lower cargo floor and vehicle height

- Protection from mud and water required for drive line components on amphibious vehicles

- Reduction in the amount of vibration present in the vehicle structure

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SUSPENSION SYSTEMS

If a car is running on perfectly smooth, level road, it will receive hardly any shock from the surface

of the road However, since there are generally many holes and bumps in most roads, the car iscontinually subjected to road shock If there were no preparations made to reduce this shock to atolerable level, several problems would arise The passengers would experience uncomfortablevibration, oscillation, and jolting The vehicle would be difficult to handle and severe shock coulddamage the vehicle or the passengers as well as the baggage being carried In order to improveboth riding comfort and driving stability, an arrangement of springs and rods is therefore providedbetween the wheels and the vehicle body to reduce the amount of shock and oscillation that istransmitted directly to the body

The suspension system works with the tires, frame or unitized body, wheels, wheel bearings, brakesystem and steering system All of the components of these systems work together to provide asafe and comfortable means of transportation The suspension system functions are as follows:

- Provide a smooth, comfortable ride by allowing the wheels and tires to move up and downwith minimum movement of the vehicle

- Work with the steering system to help keep the wheels in correct alignment

- Keep the tires in firm contact with the road, even after striking bumps or holes in the road

- Allow rapid cornering without extreme body roll (vehicle leans to one side)

- Allow the front wheels to turn from side to side for steering

- Prevent excessive body squat (body tilts down in rear) when accelerating or with heavyloads

- Prevent excessive body dive (body tilts down in the front) when braking

NONINDEPENDENT SUSPENSION (Solid Axle)

The non-independent suspension has

both left and right wheels attached to the

same solid axle When one tire hits a

bump in the road, its upward movement

causes a slight tilt in the other wheel

INDEPENDENT SUSPENSION

The independent suspension allows one wheel to

move up and down with a minimum effect on the

other wheels Since each wheel is attached to its

own suspension, movement of one wheel does

not cause direct movement of the wheel on the

opposite side of the vehicle With the independent

front suspension the use of ball joints provides

pivot points for each wheel In operation, the

swiveling action of the ball joints allows the wheel

and spindle assemblies to be turned left and right

and to move up and down with changes in road

surfaces This type of suspension is most widely

used on modern vehicles

FRONT SUSPENSION

A big difference between the front and rear suspensions is that the front wheels have to be steered.When a car corners or goes over bumps, it is subjected, via the wheels, to a variety of forces Thesuspension must be able to prevent these forces from deflecting the car from the course selected

by the driver Also, it must not allow the wheels to wobble, move forward, backward and sideways,

or alter their angle of tilt to any serious degree, as this would interfere with the handling of the car

a MacPherson strut type

The strut type suspension is composed of the lower arms,

strut bars, stabilizer bar and strut assemblies The coil

springs are mounted on the strut assembly, and the shock

absorber is built into the strut assembly One end of the

lower arm is attached to the front side member via a rubber

bushing, and can move freely up and down The other end of

mounted on the steering knuckle arm by means of a ball

joint

Since the shock absorber acts as a part of the suspension

linkage, besides being able to stand up to and absorb road

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[Independent suspension-4 link system]

[MacPherson strut type]

shock and oscillation, it must also be strong enough to bear

the vertical load that is placed on it Its top end is mounted

on the fender apron via the upper support, which is

composed of a rubber cushion and a bearing It can turn

freely about its axis The bottom end of the strut assembly is

fastened to the steering knuckle arm with bolts

The strut bars withstand the force being exerted from the wheels in the longitudinal direction Oneend is fastened to the lower arm and the other end is mounted via a rubber cushion to a strut barbracket welded to the front cross member

b Double wishbone type

This type is called because the lower and upper arms are the shape of wishbones The spindle is ahighly complex construction in this system, as are the wishbones themselves This rapidlybecoming one of the most favored suspension types for new cars as it gives excellent road-holdingcapabilities while taking up very little room under the car

On the wishbone type, when the vehicle body is rolling, the wheels tilt in the same direction as thebody does Therefore, the wheels try to go in a direction opposite to the direction the vehicle isbeing turned in As a result, if the wishbone type suspension is used for the front suspension, thevehicle has a tendency to understeer, but if it is used for the rear suspension, oversteering tends tooccur

REAR SUSPENSION

In most vehicle, the rear suspension must carry most of the extra weight of the passengers andluggage This leads to a difficult problem If the suspension springs are made hard or stiff to handlethis extra load, they will be too hard for the driver who drives alone on the other hand, if soft, theywill be too soft when the car is fully loaded The same also applies to the shock absorbers Thisproblem can be solved by using coil springs or other types of leaf springs having a variable springconstant; oil-filled shock absorbers; different types of independent suspension

SPRUNG WEIGHT AND UNSPRUNG WEIGHT

All of the weight of the body which is supported by vehicle springs is called sprung weight Thisincludes the body, frame, engine, transmission and etc On the other hand, unsprung weight is theweight of parts which is not supported by springs This includes tires, wheels, axles and etc

The greater sprung weight of the vehicle is obtained, the better riding comfort becomes Becausethe tendency to be affected by the shock or oscillation delivered from the road surface through thespring decreases as the sprung weight becomes larger

SIMPLIFIED SUSPENSION MODEL

Following picture is a simplified model of vehicle suspension This model is enough to explain the function of suspension system

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[Figure 1 Simplified

suspension model] [Figure 2 Vibration of Sprung weight/Unsprung weight]

m1 = Sprung weight , m2 = Unsprung weight, k1 = Suspension spring rate,

k2 = Tire spring rate, c1 = Damper damping rate, c2 = Tire damping rate

When an amplitude ‘a’ is applied to the simplified suspension model (Figure1), Figure 2 shows thevariation of amplitude of m1 and m2 at each frequency band

According to the Figure 2, m1 and m2 has resonance affecting the amplitude of each other C1 andC2 have an effect on amplitude at resonance, however they do not affect the resonance frequency.The resonance frequency of sprung weight or unsprung weight, that is, natural frequency is,

Natural frequency (sprung weight), fn1 = 0.5π (√k1/m1) - (1)

Natural frequency (unsprung weight) fn2 = 0.5π (√(k1+k2)/m2) - (2)

For the ride feeling it is better to reduce the suspension spring rate k1 and increase the sprungweight m1 However when the natural frequency of sprung weight fn1 is getting reduced,seasickness is more frequently experienced The fn1 range of vehicle is usually at 1.1 ~ 1.4Hz.Natural frequency of the unsprung weight fn2 is usually little bit higher than fn1 When the fn2 isincreasing, ride feeling is poor because oscillation acceleration of the sprung weight increases due

to resonance of the unsprung weight

However, when the fn2 is low, road holding by tires is poor Therefore the natural frequency of theunsprung weight need to be adjusted not high and not low to prevent this Normal range of fn2 is13~16

OSCILLATION OF SPRUNG WEIGHT