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Proper wheel alignment is crucial for maintaining your vehicle's performance and safety. This guide explores three types of alignments, common alignment issues, and adjustments needed for camber, caster, and toe angles. Learn how alignment affects tire wear, steering stability, and handling. Regular alignment checks can prevent premature tire wear and improve overall driving experience.
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Why ensure alignment? 1. To eliminate tire wear 2. To give vehicle proper handling • Eliminate pull, drift, wander, stiff steering and poor steering return ability
Three types of alignments • Geometric centerline (2 wheel) (POOR) • Aligns front wheels to center of vehicle • Thrust angle (2 wheel) (GOOD) • Aligns front wheels to thrust angle • Total alignment (4 wheel) (BEST) • Aligns all 4 wheels to geometric centerline • Not possible on all vehicles
Before alignment • Always check steering and suspension components for wear • Including wheel bearings • Always check tire pressure • A low tire may cause pull • Always check tire condition • Tire wear will indicate possible problems • Try to duplicate the complaint if possible
Camber • Inward or outward tilt of the top of the tire • Outward tip is positive / Inward tip is negative • If excessive (about 1 1/4 degree off) positive or negative, camber will cause tire wear • May cause pull to most positive side • Maximum cross camber usually .5deg
Caster • Forward or rearward tilt of the steering axis • Forward is negative \ rearward is positive • Positive gives steering stability and returnability • Negative decreases turning effort • May cause pull to most negative side • Maximum cross caster usually .5deg
Toe • Difference between the front and rear of the tires • Toe 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
Toe • Excessive toe in (positive) will cause wear on the outer tire edges • Excessive toe out (negative) will cause wear on the inner tire edges • Incorrect toe is THE most common cause of tire wear • Different toe side to side will cause steering wheel to be off center but will not cause pull
Camber and caster adjustments • If adjustments are possible, it will usually be at only one pivot point • Camber and caster are often adjusted together
Slotted holes • Common on MacPherson strut with 2 bolts at knuckle • Common at top of strut mount
Eccentrics • SLA may have 2 eccentrics on upper control arm bolts • MacPherson strut may have eccentric at knuckle attaching bolts • Depending on design, may be used to adjust both angles or just camber
Shims • Found mostly on vehicles with SLA suspensions • Shims come in various thickness' • Can adjust both caster and camber
Strut rod • Lengthening or shorting strut rod attached to lower control will change caster
Cradle adjustment • Some vehicles allow cradle adjustment • Can affect both caster and camber • Should only be done if manufacture recommends
Toe adjustment • Always performed as last adjustment • Adjusted by effectively lengthening or shortening tie rods • Some vehicles have only one adjustable tie rod • Sometimes toe is only adjustment possible
Steering axis inclination Included angle Diagnostic angles
Definitions • SAI a line drawn through the steering axis, as viewed from the front • SAI allows smaller camber angles but keeps load on inboard of spindle • SAI moves spindle in arc like caster • Included angle is the total of SAI + camber
SAI and IA • Both angles are used for diagnostics when bent or loose components are suspect • Many vehicles do not give specs • Side to side differences most important • 1.5 deg diff side to side or off of specs maximum allowed • Should be checked whenever camber is found to be way off
Cradle adjusting • If SAI off opposite amounts side to side suspect cradle alignment
Rear wheels • Usually only front wheel drive vehicles • Purpose is to realign thrust angle and geometric centerline • Camber and toe only angles • Rear toe or camber problems can cause lead, pull, dog tracking, tire wear
Adjusting rear wheels • Camber adjusted first if available • Toe adjustment more common than camber
Rear toe • Can be adjusted by tie rods similar to front
Rear toe and camber • Can be adjusted using eccentrics, depending on their position, similar to front end
Aftermarket shims • Full contact shims can adjust both angles