Alignment

Why ensure alignment?1. To eliminate tire wear 2. To give vehicle proper handlingEliminate pull, drift, wander, stiff steering and poor steering return ability

Three types of alignmentsGeometric centerline (2 wheel) (POOR)Aligns front wheels to center of vehicleThrust angle (2 wheel) (GOOD)Aligns front wheels to thrust angleTotal alignment (4 wheel) (BEST)Aligns all 4 wheels to geometric centerlineNot possible on all vehicles

Before alignmentAlways check steering and suspension components for wearIncluding wheel bearingsAlways check tire pressureA low tire may cause pullAlways check tire conditionTire wear will indicate possible problemsTry to duplicate the complaint if possible

CamberInward or outward tilt of the top of the tireOutward tip is positive / Inward tip is negativeIf excessive (about 1 1/4 degree off) positive or negative, camber will cause tire wearMay cause pull to most positive sideMaximum cross camber usually .5deg

CasterForward or rearward tilt of the steering axisForward is negative \ rearward is positivePositive gives steering stability and returnabilityNegative decreases turning effortMay cause pull to most negative sideMaximum cross caster usually .5deg

Camber roll

ToeDifference between the front and rear of the tiresToe in or positive toe means the front of the tires are closer than the rear of the tires Toe out or negative toe means the rear of the tires are closer than the front of the tires

ToeExcessive toe in (positive) will cause wear on the outer tire edgesExcessive toe out (negative) will cause wear on the inner tire edgesIncorrect toe is THE most common cause of tire wearDifferent toe side to side will cause steering wheel to be off center but will not cause pull

Camber and caster adjustmentsIf adjustments are possible, it will usually be at only one pivot point Camber and caster are often adjusted together

Slotted holesCommon on MacPherson strut with 2 bolts at knuckleCommon at top of strut mount

EccentricsSLA may have 2 eccentrics on upper control arm boltsMacPherson strut may have eccentric at knuckle attaching boltsDepending on design, may be used to adjust both angles or just camber

ShimsFound mostly on vehicles with SLA suspensionsShims come in various thickness'Can adjust both caster and camber

Strut rodLengthening or shorting strut rod attached to lower control will change caster

Cradle adjustmentSome vehicles allow cradle adjustmentCan affect both caster and camberShould only be done if manufacture recommends

Shim practice

Toe adjustment Always performed as last adjustmentAdjusted by effectively lengthening or shortening tie rodsSome vehicles have only one adjustable tie rodSometimes toe is only adjustment possible

Steering axis inclination Included angleDiagnostic angles

DefinitionsSAI a line drawn through the steering axis, as viewed from the frontSAI allows smaller camber angles but keeps load on inboard of spindleSAI moves spindle in arc like casterIncluded angle is the total of SAI + camber

SAI and IABoth angles are used for diagnostics when bent or loose components are suspectMany vehicles do not give specs Side to side differences most important1.5 deg diff side to side or off of specs maximum allowedShould be checked whenever camber is found to be way off

Cradle adjustingIf SAI off opposite amounts side to side suspect cradle alignment

Rear Wheel Alignment

Rear wheelsUsually only front wheel drive vehiclesPurpose is to realign thrust angle and geometric centerlineCamber and toe only anglesRear toe or camber problems can cause lead, pull, dog tracking, tire wear

Adjusting rear wheelsCamber adjusted first if availableToe adjustment more common than camber

Common adjustments

Rear toeCan be adjusted by tie rods similar to front

Rear toe and camberCan be adjusted using eccentrics, depending on their position, similar to front end

Aftermarket shimsFull contact shims can adjust both angles

Shim example

The End