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Alignment. Why alignment? 1. To eliminate tire wear 2. To give vehicle proper handling –Eliminate pull, drift, wander, stiff steering and poor steering.

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Presentation on theme: "Alignment. Why alignment? 1. To eliminate tire wear 2. To give vehicle proper handling –Eliminate pull, drift, wander, stiff steering and poor steering."— Presentation transcript:

1 Alignment

2 Why 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 u Geometric centerline (2 wheel) (POOR) –Aligns front wheels to center of vehicle u Thrust angle (2 wheel) (GOOD) –Aligns front wheels to thrust angle u Total alignment (4 wheel) (BEST) –Aligns all 4 wheels to geometric centerline –Not possible on all vehicles

4 Before alignment u Always check steering and suspension components for wear –Including wheel bearings u Always check tire pressure –A low tire may cause pull u Always check tire condition –Tire wear will indicate possible problems u Try to duplicate the complaint if possible

5 Camber u Inward or outward tilt of the top of the tire u Outward tip is positive / Inward tip is negative u If excessive (about 1 1/4 degree off) positive or negative, camber will cause tire wear u May cause pull to most positive side u Maximum cross camber usually.5deg

6 Caster u Forward or rearward tilt of the steering axis u Forward is negative \ rearward is positive u Positive gives steering stability and returnability u Negative decreases turning effort u May cause pull to most negative side u Maximum cross caster usually.5deg

7 Camber roll

8 Toe u Difference between the front and rear of the tires u Toe in or positive toe means the front of the tires are closer than the rear of the tires u Toe out or negative toe means the rear of the tires are closer than the front of the tires

9 Toe u Excessive toe in (positive) will cause wear on the outer tire edges u Excessive toe out (negative) will cause wear on the inner tire edges u Incorrect toe is THE most common cause of tire wear u Different toe side to side will cause steering wheel to be off center but will not cause pull

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

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

12 Eccentrics u SLA may have 2 eccentrics on upper control arm bolts u MacPherson strut may have eccentric at knuckle attaching bolts u Depending on design, may be used to adjust both angles or just camber

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

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

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

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17 Shim practice

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21 Toe adjustment u Always performed as last adjustment u Adjusted by effectively lengthening or shortening tie rods u Some vehicles have only one adjustable tie rod u Sometimes toe is only adjustment possible

22 Steering axis inclination Included angle Diagnostic angles

23 Definitions u SAI a line drawn through the steering axis, as viewed from the front u SAI allows smaller camber angles but keeps load on inboard of spindle u SAI moves spindle in arc like caster u Included angle is the total of SAI + camber

24 SAI and IA u Both angles are used for diagnostics when bent or loose components are suspect u Many vehicles do not give specs u Side to side differences most important u 1.5 deg diff side to side or off of specs maximum allowed u Should be checked whenever camber is found to be way off

25 Cradle adjusting u If SAI off opposite amounts side to side suspect cradle alignment

26 Rear Wheel Alignment

27 Rear wheels u Usually only front wheel drive vehicles u Purpose is to realign thrust angle and geometric centerline u Camber and toe only angles u Rear toe or camber problems can cause lead, pull, dog tracking, tire wear

28 Adjusting rear wheels u Camber adjusted first if available u Toe adjustment more common than camber

29 Common adjustments

30 Rear toe u Can be adjusted by tie rods similar to front

31 Rear toe and camber u Can be adjusted using eccentrics, depending on their position, similar to front end

32 Aftermarket shims u Full contact shims can adjust both angles

33 Shim example

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36 The End


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