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Presentation on theme: "Alignment."— 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
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


17 Shim practice




21 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

22 Steering axis inclination Included angle
Diagnostic angles

23 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

24 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

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

26 Rear Wheel Alignment

27 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

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

29 Common adjustments

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

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

32 Aftermarket shims Full contact shims can adjust both angles

33 Shim example



36 The End

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