BASIC WHEEL
ALIGNMENT
16/06
SHOCK ABSORBER, SUSPENSION, BRAKES, TOWBARS AND WHEEL ALIGNMENT SPECIALISTS
Basic Wheel Alignment
There are many reasons why a wheel alignment is to It is a total waste of your customer’s money and your be considered an important repair/service operation on time if a wheel alignment takes place and there are ball any car. It is therefore necessary to understand the basic tie rod operation ends and/or bushes There are many reasons why a wheel alignment is to be considered an importantjoints, repair/service on any car. that are not within principles involved withinthe the steering geometry the the steering permitted acceptable serviceable allowances. It is therefore necessary to understand basic principles involvedofwithin geometry of the vehicle. This tech stop is designed to give youisan insight into technical of wheel alignments and the reasons why it vehicle. This tech stop designed tothe give you anaspects insight For example, 2mm of wheel bearing movement will is important to the take technical this operation very seriously. into aspects of wheel alignments and the affect the toe reading by 4mm, this is tyre wearing There are reasons 6 good reasons why you should take wheel alignments seriously: why it is important to take this operation very territory. Vehicle control seriously. Directional stability If a wheel alignment is performed on a car and it has Maximum effect from the foot print the tyre There are 6 good reasons whyofyou should take wheel worn components, then there is a high probability that Long tyre life seriously: alignments the car will still wear tyres, pull to one side and the Fuel economy • Vehicle control. steering wheel will not be straight. Braking effect
Wheel Alignment
• Directional stability. What will happen now, is that the customer will come t isPre to be considered an important repair/service operation on any car. – Alignment Inspection: back to your store and complain, this is not a good principles involved within the steering geometry of the vehicle. • Maximum effect from the foot print of the tyre. t into theany technical of wheel alignments reasons why it and suspension situation, the customer to you in the first place Before wheel aspects alignment is to be performedand on the a car, the steering is to beaschecked for worn came or y.damaged components. • Long tyre life. because you are the steering and suspension expert wheel It is aalignments total wasteseriously: of your customer’s money and your time if a wheel alignment and takes“No placeBull”. and there are ball joints, • Fuel economy.
tie rod ends and/or bushes that are not within permitted acceptable serviceable allowances. Wheels and Tyres: For example, 2mm of effect. wheel bearing movement will affect the toe reading by 4mm, this is tyre wearing territory. • Braking the If tyre a wheel alignment is performed on a car and it has worn components, then there is a high probability that the car A worn tyre is a history story on what happened within Pretyres, – Alignment Inspection: will still wear pull to one side and the steering wheel will not be straight. the suspension, can situation, tell you aaslot. What will happen now, is that the customer will come back to your store and complain, this is not aitgood Before any wheel alignment is to be performed on a car, the customer came to you in the first place because you are the steering and suspension expert and “No Bull”.
the steering and suspension is to be checked for worn or
damaged Wheels and Tyres: components.
A worn tyre is a history story on what happened within the suspension, it can tell you a lot. Alignment Status Issue
Tyre Condition
on a car, the steering and suspension is to be checked for worn or
d your time if a wheel alignment takes place and there are ball joints, ermitted acceptable serviceable allowances. t will affect the toe reading by 4mm, this is tyre wearing territory. it has worn components, then there is a high probability that the car ering wheel will not be straight. l come back to your store and complain, this is not a good situation, as ause you are the steering and suspension expert and “No Bull”.
Toe Toe
Over Over
Under Under
Inflated ened within the suspension, it can tell you a lot. Inflated
Under Inflated
Inflated Inflated
Camber/Caster Scalloped Camber/ Scalloped Shock
Caster
Angles Out
Incorrect Toe
Feather or sawtooth wear
Incorrect Camber
One edge worn (Smooth Edge)
Components Worn Shock/ Worn Component
BalanceScallopedOut of round & out Camber/Caster
Cupper or scalloped wear
problems
of balance
Random bald spots
Inflation levels
Under inflated
Both edges
Over Inflated
Worn tread centre
The Driver
Corners quickly, brakes hard, accelerates fast, drives on rocky surfaces, overloads vehicle
Worn sidewalls, radial feathering, torn tread, both edges
Shock Absorbers
Absorbers
Shock Absorbers
Straight advice, specialists you understand and...
-
The same construction The same tread design The same tread depth On the same sized rim If directional, all rotating in the correct direction
Ride Heights and Load Distribution: BASIC WHEEL
16/06
ALIGNMENT
Prior to conducting a wheel alignment on a vehicle, it from side to side. It is reasonable to expect a vehicle to measurement, unless it is excessive. If in doubt always firm level surface.
SHOCK ABSORBER, SUSPENSION, In BRAKES, order toTOWBARS maximise AND WHEEL ALIGNMENT SPECIALISTS
Always check the tyre pressure and make sure that all the rims are the same size and have the same “Off – Set”
the tyre life and handling of vehi essential to perform the wheel alignment operation wh it’s normal load. When one cone is greater than the other a pull will be induced in to the car.
Camber The main purpose of camber these days is to maintain Any wheel alignment on a car with unmatched or even tyre contact across the entire tread surface. This is the angle of edges the wheel, measured in degre severely worn tyres will create a problem. Tyres on the helps reduceCamber tyre wear on the tyre’s and improves wheel is leaning out from the centre Always check the tyre pressure and make sure that all the rims are the same size and have the same “Off – Set”of the car, the same axle should be: the cornering ability of the vehicle.
- The same tread depth
Any wheel alignment on a car with unmatched or severely worn tyres If willthe create a problem. on the same axle it will ca negative. camber is Tyres out of adjustment, should be: far negative, for instance, then the tire will wear on the - The same size - The same construction - The same tread design - The same tread depth - On the same sized rim - If directional, all rotating in the correct direction
- On the same sized rim
Ride Heights and Load Distribution:
- The same size - The same construction - The same tread design
- If directional, all rotating in the correct direction Prior to conducting a wheel alignment on a vehicle, it is very important that the vehicle to have an even ride height
from side to side. It is reasonable to expect a vehicle to have rake to the front, so front to rear height is not a critical
Ride Heights and Load Distribution: measurement, unless it is excessive. If in doubt always check, and remember when doing so, the vehicle is to be on a firm level surface.
Prior to conducting a wheel alignment on a vehicle, it In order to maximise the tyre life and handling of vehicles designed for load carrying or towing purposes, it is is very important that the vehicle to have an even ride essential to perform the wheel height from side to side. It is reasonable to expect a alignment operation whilst the vehicle is in it’s usual operating situation, i.e. carrying it’s normal load. vehicle to have rake to the front, so front to rear height Camberit is excessive. If in is not a critical measurement, unless doubt always check, and remember when doing so, the Camber is the angle of the wheel, measured in degrees, when viewed from the front of the vehicle. If the top of the vehicle is to be on a firm level surface. wheel is leaning out from the centre of the car, then the camber is positive ,if it's leaning in, then the camber is
negative. 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 In order to maximise the tyre life and handling of far negative, for instance, then the tire will wear on the inside of the tread. vehicles designed for load carrying or towing purposes, Positive or negative camber causes the tyre to bec it is essential to perform the wheel alignment operation When a cone is rolled it rolls in a circle around its whilst the vehicle is in it’s usual operating situation, i.e. A vehicle with equal camber left and right will no carrying it’s normal load.
Camber
other. When one cone is greater than the other a p
Camber is the angle of the wheel, measured in degrees, The main purpose of camber these days is when viewed from the front of the vehicle. If the top helps reduce tyre wear on the tyre’s edges of the wheel is leaning out from the centre of the car, then the camber is positive ,if it’s leaning in, then the camber is negative. 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 Camber: Positive or negative camber causes the tyre wear on the inside of the tread.Positive or negative camber causes the to become tapered across its tread, effectively creating a cone. to tyre become tapered across its tread, effectively creating When a cone is rolled it rolls in a circle around its tip. Positive or negative camber causes the tyre to become cone. A vehicle with equal camber left andaright will not have a camber induced pull as one side counteracts the tapered across its tread, effectively a cone. other. creating When one cone is greater than the other a pull will be induced in to the car. When a cone is rolled it rolls in a circle around its tip. The main purpose of camber these days is to maintain even tyre contact across the entire tread surface. This
A vehicle with equal camber left and righttyre willwear noton have a edges and improves the cornering ability of the vehicle. helps reduce the tyre’s camber induced pull as one side counteracts the other.
Straight advice, specialists you understand and...
to main and imp
too much positive, the steering will be heavier (especially with non-power steering as
may kick when you hit a bump. Caster has little affect on tire wear, except where un
have input into the steering to counteract the “pull”. In this case there maybe noticeab
BASIC WHEEL 16/06
ALIGNMENT SHOCK ABSORBER, SUSPENSION, BRAKES, TOWBARS AND WHEEL ALIGNMENT SPECIALISTS
Caster
Toe In and Toe Out
Caster is the angle of this steering pivot, measured in Toe is a measurement of how much the front and/or degrees, when viewedPurpose from the side of the vehicle. If rear wheels are turned in or out from a straight-ahead the top of the pivot is leaning toward the rear of the car, position. When the wheels are turned in, toe is positive then the caster is positive, if it is leaning toward the front, (+). When the wheels are turned out, toe is negative Caster is the angle that most affects directional stability primarily on rear wheel drive it is negative. If the caster is out of adjustment, it can (-). The actual amount of toe is normally only a fraction provides 3 important characteristics. Caster cause problems in straight line tracking. If the caster is of a degree. The purpose of toe is to ensure that the different from side to side, the vehicle will pull to the side wheels roll parallel. Toe also serves to offset the small Caster the angle this steering pivot, measured inIfdegrees, whenisviewed from the side of the top ofsystem that occur when withis the leastofamount of caster.feel the ofthe thevehicle. wheelIfsupport 1.positive Steering orcaster feed back deflections equal but too negative, the steering will be light and the the vehicle is rolling forward. In other words, with the the pivot is leaning toward the rear of the car, then the caster is positive, if it is leaning toward the front, it is negative. 2.be difficult Directional stability vehicle will wander and to keep in a straight vehicle standing still and the wheels set with toe-in, the If the caster is out of adjustment, it can cause problems in straight line tracking. If the caster is different from side to 3. self-centring line. If the caster is equal butSteering has too much positive, wheels tend to roll parallel on the road when the vehicle side, the vehicle will pull to the side with the least amount of positive caster. If the caster is equal but too negative, the the steering will be heavier (especially with non-power is moving. Improper toe adjustment will cause premature steering will be light and the vehicle will wander and be difficult to keep in a straight line. If the caster is equal but has steering assistance) and the steering wheel may kick tire wear and cause steering instability. Toe in and Toe with – out too when much positive, steeringCaster will be–heavier (especially non-power you hit the a bump. has little affect on tire wear, steering assistance) and the steering wheel Purpose mayexcept kick when you hit a bump.caster Caster causes has little affect on tireto wear, except where unequal caster causes the driver to where unequal the driver have eering pivot, measured in degrees, when viewed from the side of the vehicle. If the top of Toe is the a measurement of maybe how Toe much the front and/or rearangle wheels turned in or ou input thesteering steering to counteract theIn“pull”. In there this have inputinto into the to counteract “pull”. this case noticeable edge wear on the tyres. angle is the wheel alignment that are can have he rear of thecase car, then the maybe caster is noticeable positive, if it is leaning toward the front, it is negative. there edge wear on the tyres. the toe greatest effect on (+). tyre wear because it controlsare turned ou When the wheels are turned in, is positive When the wheels ment, it can cause problems in straight line tracking. If the caster is different from sidethe to direction of the tyres on the road in relation to one amount of toe is normally onlythea fraction of a degree. The purpose of toe is to ensure the side with the least amount of positive caster. If the caster is equal but too negative, another. Toe angles were first examined and adjusted also serves to offset the small has deflections of theknown wheel support system it first became that a vehicle’s motionthat had occur whe vehicle will wander and be difficult to keep in a straight line. If the caster is equal but when In other words, with the vehicle standing still and the wheels set with the effect of forcing the wheels away from parallel. toe-in, the w ng will be heavier (especially with non-power steering assistance) and the steering wheel
when thecaster vehicle is driver moving. mp. Caster has little affect on tire wear, road except where unequal causes the to
o counteract the “pull”. In this case thereinstability. maybe noticeable edge wear on the tyres.
Improper toe adjustment will cause prematur
Purpose Caster is the angle that most affects directional stability primarily on rear wheel drive vehicles. Positive Caster provides 3 important characteristics. 1. Steering feel or feed back 2. Directional stability 3. Steering self-centring Toe – in and Toe – out
Types of Castor
ToePurpose is a measurement of how the front rearPositive wheels Caster are turned in or out from a straight-ahead position. affects directional stability primarily on much rear wheel driveand/or vehicles. eristics. When the wheels are turned in, toe is positive (+). When the wheels are turned out, toe is negative (-). The actual Caster is isthe angleonly thatPurpose affects directional stability amount of toe normally amost fraction of a degree. The purpose of toe is to ensure that the wheels roll parallel. Toe on rear drive vehicles. Positive Caster alsoprimarily serves to offset the wheel small deflections of the wheel support system that occur when the vehicle is rolling forward. k In other words,3with the vehicle standing still and the wheels set with toe-in, the wheels tend to roll parallel on the provides important characteristics. road when the vehicle is moving. adjustment cause premature tirethat wear can and cause steering Toe Improper angle istoethe wheelwill alignment angle have the Toe In & Toegreatest Out 1. Steering feel or feed back instability.
2. Directional stability
effect on tyre wear b of the tyres on the road in relation to one another. Toe angles were first examined and known that a vehicle’s motion had the effect of forcing the wheels away from parallel
w much the 3. front and/or rear wheels are turned in or out from a straight-ahead position. Steering self-centring d in, toe is positive (+). When the wheels are turned out, toe is negative (-). The actual nly a fraction of a degree. The purpose of toe is to ensure that the wheels roll parallel. Toe ll deflections of the wheel support system that occur when the vehicle is rolling forward. hicle standing still and the wheels set with toe-in, the wheels tend to roll parallel on the moving. Improper toe adjustment will cause premature tire wear and cause steering Purpose
Straight advice, specialists you understand and...
Toe angle is the wheel alignment angle that can have the greatest effect on tyre wear because it controls the direction of the tyres on the road in relation to one another. Toe angles were first examined and adjusted when it first became
BASIC WHEEL 16/06
ALIGNMENT SHOCK ABSORBER, SUSPENSION, BRAKES, TOWBARS AND WHEEL ALIGNMENT SPECIALISTS
Toe Out on turns
Steering Axis Inclination (S.A.I.)
When you steer a car through a turn, the outside front wheel has to navigate a wider arc then the inside wheel. For this reason, the inside front wheel must steer at a sharper angle than the outside wheel.Two degrees of toe change can equate to 12mm of toe – out
SAI is the measurement in degrees of the steering pivot line when viewed from the front of the vehicle. This Toe out turns angle, when added toon the camber to form the included angle (see below) causes the vehicle to lift slightly when Whenaway you steer a car a turn, the outside front wheel has to you turn the wheel from a through straight ahead position. reason, the insideoffront musttosteer at a the sharper angle than t This action uses the weight the wheel vehicle cause steering wheel two to return thechange center let go degrees to of toe canwhen equate you to 12mm of toe – out of it after making a turn. Because of this, if the SAI is different from side to side, it will cause a pull at very Purpose slow speeds. Most alignment machines have a way to When the car is measure SAI; however it is not separately adjustable. different axes, if The most likely cause for SAI being out of specificationscrubbing will oc is bent parts which must be replaced to correct the avoid the need fo around a curve. condition. SAI is also referred to as KPI (King Pin Inclination) on trucks and old cars with kingpins insteadMeasuring of ball joints.
Purpose When the car is turning a corner, the front wheels rotate on different axes, if the geometry does not allow for this, then tyre scrubbing will occur. The intention of Ackermann geometry is to avoid the need for tyres to slip sideways when following the path around a curve.
Measuring
Toe-out on turns is measured by the turning angle gauges (turn plates) that are a part of every wheel Toe-out on turns alignment machine. The readings are either directly on Purpose plates) that are a the turn plate or they are measured electronically and readings are eith displayed on the screen. Wheel alignment specifications In today’s cars S.A.I. is also used as the primary electronically an directional stability angle and reduces the need for specifications wi will usually provide the measurements for toe-out on caster. It provides excellent straight line steering and turns. They will turns. They will give an angle for the inside wheel and wheel such as 20 self-centring steering. the outside wheel such as 20: for the inside wheel and wheel. Make sur Toe out on turns 18: for the outside wheel. Make sure that the readings Another thing to keep in mind, all the Wheel Alignmentthe wheels are st the inside wheel are at zero on each side when the wheels are straight geometry settings are measured and adjusted whilst the Whenturn you steer a car through a turn, outside wheel has car to navigate a wider arc then the inside wheel. For this ahead, then the steering wheel sothe that the front inside is stationarySteering (Static), butInclination they are(S.A.I.) calculated for when Axis wheel isreason, at the the inside theatoutside insidespec. front then wheel check must steer a sharper angle than thecar outside Remembering the is inwheel. motion (Dynamic).the degree wheel, wheel. two degrees of toe change can equate to 12mm of toe – out
SAI is the measurement in degree front of the vehicle. This angle, wh (see below) causes the vehicle to straight ahead position. This act When the car is turning a corner, the front wheels rotate on steering wheel to return to the c different axes, if the geometry does not allow for this, then tyre Because of this, if the SAI is diff scrubbing will occur. The intention of Ackermann geometry is to slow speeds. Most alignment mach avoid the need for tyres to slip sideways when following the path separately adjustable. The most li around a curve. must be replaced to correct the co Inclination) on trucks and old cars Measuring
Purpose
Toe-out on turns is measured by the turning angle gauges (turn Steering Axis Inclination plates) that are a part of every wheel alignment machine. The (S.A.I.) Purpose readings are either directly on the turn plate or they are measured Final Note: When the head the wheel electronicallyOne and displayed on the screen.cars Wheel alignment In today’s S.A.I. isof also used as the alignment primary directional stabilit machine has been fitted to the wheel, a “run-out” is to be specifications will usually provide the measurements for toe-out excellent straight line steering andon self-centring steering. turns. They will give an angle for procedure the inside wheel and the outside performed. This neutralises any imperfection Another thing in mind, all the readings. Wheel Alignment geometry wheel such asof 20:the for head the inside wheel and 18: to forkeep the outside to the rim and will give accurate A stationary (Static), but they calculated for when the car is in mo wheel. Make sure that the readings are at zero on each sideare when lot of modern machines have this built in to their process, the wheels are straight ahead, then turn the steering wheel so that butisthe older doNote: not it iswheel. tothe behead performed the inside wheel at the insidemachines spec. check theand outside Onethen Final When of the wheel align
manually on EVERY wheel alignment.
wheel, a “run-out” is to be performed. This proced the head to the rim and will give accurate reading built in to their process, but the older machines do SAI is the measurement in degrees of the steering pivot line when viewed from the on the EVERY front of the vehicle. This angle, when added to themanually camber to form includedwheel angle alignment.
Steering Axis Inclination (S.A.I.)
Straight advice, specialists you understand and...
(see below) causes the vehicle to lift slightly when you turn the wheel away from a straight ahead position. This action uses the weight of the vehicle to cause the steering wheel to return to the center when you let go of it after making a turn.