Wheel Alignment

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Wheel Alignment
CASTER
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Effects of Caster

• High Positive Caster increases ( )
• Straight ahead stability
• Steering effort required is high
• Steering wheel return to center
• Road Shock felt from bumps
• More Negative Caster ( -- )
• No Straight ahead stability
• Steering effort is light
• Wheel not returning to center
• Smooth ride, little road shock

Uneven Caster will cause the vehicle to pull
towards the side with less Caster (more Negative
-) ½ degree or more
Not a tire wearing angle!!!!
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Caster can be set unevenly to counter act for
road crown pull.

• Usually ½ degree or more on the downhill side.
• Caster trail is the distance between the caster
  line and the tire point of contact.

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CAMBER
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Camber The inward or out ward tilt of the
centerline of the tire.
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Camber

• The more camber you have, the more the load is
  placed on the outside of the tire.
• Excessive positive or negative camber can cause
  tire wear on the edges

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Camber can cause a car to pull to one side
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Effects of Camber

• Tire wearing angle
• Directional control angle
• Pull towards the side with more positive camber
• Excessive Camber Accelerates bearing wear
• Load is not evenly set on bearings.
• Positive wears the inner bearing
• Negative wears the outer bearing

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Influences on Camber

• Uneven Loading
• Body roll during turns
• Road Crown
• Rough road Surfaces
• Suspension Wear
• Suspension Damage
• Tire size
• Caster

Faster cornering wears out edges of tires!!!!
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Camber can be set unevenly to counter act for
road crown pull.

• Cross Camber should never exceed ½ degree
• Camber will pull to the most positive side
• Camber Roll
• Caster angle may produce a change in the camber
  angle when the wheels are turned

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Camber is adjustable on most vehicles
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Toe
Toe in Toe out
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Darting
Darting
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Wander
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Toe

• Toe in Darting
• Toe out Wander

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Effects of Toe

• Tire wear
• Scuffing sideways
• Scuffing is Drag and hop!
• Wear tends to be the same on both tires, unlike
  Camber wear
• Directional control angle
• Can cause shimmy!
• Diagonal Wipe on the rear tires if toe is
  excessive
• Lots of rotations!
• Toe Change can occur as suspension travels up and
  down.
• Measure toe change at 1 inch increments
• Should be no change!
• Check length and height of tie rods!!!

City driving can cause unusual tire wear that
might be blamed on Toe problems!!
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SAI

• Steering Axis Inclination

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SAI

• The inward tilt at the top of the strut.
• (looking from the front)

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SAI

• The inward tilt at the top of the strut.
• (looking from the front)

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SAI and Included angle

• Include angle
• SAI pos. camber

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Effects of SAI

• Ensures Steering stability
• FWD use more SAI because of small Caster
• Helps with Steering Wheel returnability
• Uses Gravity to assist

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Diagnosis with SAISLA Strut/SLA
SAI Camber Included Angle Diagnosis
Correct lt spec lt spec Bent steering Knuckle
lt Spec gt Spec Correct Bent lower control arm
lt Spec gt Spec gt Spec Bent lower arm Knuckle or spindle
gt Spec lt spec Correct Bent upper control arm

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Diagnosis with SAI Strut Suspensions
SAI Camber IA Diagnosis
Correct lt spec lt spec Bent spindle or strut
Correct gt Spec gt Spec Bent spindle or strut
lt spec gt Spec Correct Bent control arm or strut
lt spec lt spec gtSpec lt spec gt Spec lt spec Bent control arm or strut or spindle. strut tower out at top strut tower in at top
gt Spec lt spec correct Strut tower in at top
gt Spec gt Spec gt Spec Strut tower in at top And bent spindle strut

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0 bump steer

• No toe angle change.
• Need to Check for this at 1 inch increments
• 3 factors affect bump steer
• Tie rod length
• Relative heights of inner and outer tie rod ends
• Steering arm length

Zero SAI would Major bump steer
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Positive Scrub Radius

• Positive
• scrub radius
• RWD vehicles
• Sport cars
• Feel the steering wheel tug when braking
• Road feel
• Driver Involvement needed

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Negative Scrub radius

• Used on
• Split diagonal braking systems
• Self Correcting when braking
• No driver involvement needed
• No road feel

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• Effects of
• Larger tire
• smaller tire
• deep dish
• wheel

Larger Scrub harder to turn and increased
wear Smaller Scrub easy turns Braking stability
- Negative has greater directional
stability Positive decreases braking stability
(aftermarket rims)
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Turning Angle Setback Thrust Angle.
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Turning Angle
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Setback
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Thrust
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The End

Thanks to Specialty Products Company