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Alignment

Alignment. 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

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Alignment

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  1. Alignment

  2. 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

  3. 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

  4. 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

  5. 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

  6. 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

  7. Camber roll

  8. 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

  9. 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

  10. Camber and caster adjustments • If adjustments are possible, it will usually be at only one pivot point • Camber and caster are often adjusted together

  11. Slotted holes • Common on MacPherson strut with 2 bolts at knuckle • Common at top of strut mount

  12. 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

  13. Shims • Found mostly on vehicles with SLA suspensions • Shims come in various thickness' • Can adjust both caster and camber

  14. Strut rod • Lengthening or shorting strut rod attached to lower control will change caster

  15. Cradle adjustment • Some vehicles allow cradle adjustment • Can affect both caster and camber • Should only be done if manufacture recommends

  16. Shim practice

  17. 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

  18. Steering axis inclination Included angle Diagnostic angles

  19. 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

  20. 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

  21. Cradle adjusting • If SAI off opposite amounts side to side suspect cradle alignment

  22. Rear Wheel Alignment

  23. 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

  24. Adjusting rear wheels • Camber adjusted first if available • Toe adjustment more common than camber

  25. Common adjustments

  26. Rear toe • Can be adjusted by tie rods similar to front

  27. Rear toe and camber • Can be adjusted using eccentrics, depending on their position, similar to front end

  28. Aftermarket shims • Full contact shims can adjust both angles

  29. Shim example

  30. The End

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