4Effects of CasterHigh Positive Caster increases ( + )Straight ahead stabilitySteering effort required is highSteering wheel return to centerRoad Shock felt from bumpsMore Negative Caster ( -- )No Straight ahead stabilitySteering effort is lightWheel not returning to centerSmooth ride, little road shockUneven Caster will cause the vehicle to pull towards the side with less Caster (more Negative -)½ degree or moreNot a tire wearing angle!!!!
5Caster 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.
10Effects of Camber Tire wearing angle Directional control angle Pull towards the side with more positive camberExcessive Camber Accelerates bearing wearLoad is not evenly set on bearings.Positive wears the inner bearingNegative wears the outer bearing
11Influences on Camber Uneven Loading Body roll during turns Road Crown Rough road SurfacesSuspension WearSuspension DamageTire sizeCasterFaster cornering wears out edges of tires!!!!
12Camber can be set unevenly to counter act for road crown pull. Cross Camber should never exceed ½ degreeCamber will pull to the most positive sideCamber RollCaster angle may produce a change in the camber angle when the wheels are turned
22Effects of ToeTire wearScuffing sidewaysScuffing is Drag and hop!Wear tends to be the same on both tires, unlike Camber wearDirectional control angleCan cause shimmy!Diagonal Wipe on the rear tires if toe is excessiveLots of rotations!Toe Change can occur as suspension travels up and down.Measure toe change at 1 inch incrementsShould be no change!Check length and height of tie rods!!!City driving can cause unusual tire wear that might be blamed on Toe problems!!
29Effects of SAI Ensures Steering stability FWD use more SAI because of small CasterHelps with Steering Wheel returnabilityUses Gravity to assist
30Diagnosis with SAI SLA & Strut/SLA CamberIncluded AngleDiagnosisCorrect< specBent steering Knuckle< Spec> SpecBent lower control armBent lower arm & Knuckle or spindleBent upper control arm
31Diagnosis with SAI Strut Suspensions CamberIADiagnosisCorrect< specBent spindle or strut> SpecBent control arm or strut>SpecBent control arm or strut or spindle.strut tower out at topstrut tower in at topcorrectStrut tower in at topAnd bent spindle & strut
320 bump steer Zero SAI would = Major bump steer No toe angle change. Need to Check for this at 1 inch increments3 factors affect bump steerTie rod lengthRelative heights of inner and outer tie rod endsSteering arm lengthZero SAI would = Major bump steer
33Positive Scrub Radius Positive scrub radius RWD vehicles Sport cars Feel the steering wheel tug when brakingRoad feelDriver Involvement needed
34Negative Scrub radius Used on Split diagonal braking systems Self Correcting when brakingNo driver involvement neededNo road feel