AUMT 1316 - Wheel Alignment 11/15/11 Steering and Suspension Steering and Suspension Camber Angle • Camber is the amount that the centerline of the wheel tilts away from true Wheel Alignment vertical when viewed from the front of the vehicle • Camber places the tire tread flat on the road Donald Jones reducing tire wear and improving vehicle Brookhaven College handling • Excessive camber will cause wear on the edge of the tire’s tread Steering and Suspension Steering and Suspension Camber Split Caster Angle • Camber split is the • Positive caster is the difference between the rearward tilt of the left and right camber steering axis settings • Negative caster is the • Excessive camber split forward tilt of the steering axis will cause a vehicle to pull to the most positive • The vehicle will pull to the least positive side side • Not a tire wear angle • Camber split should be limited to ½ a degree or • Caster aides in directional stability and steering less to prevent vehicle wheel return pull Steering and Suspension Steering and Suspension Caster and Ride Height Toe Angle • It is important to • Inward or outward variation of tires from a consider normal straight ahead position vehicle loading • Toe in is referred to as when performing positive toe • Toe out is referred to as alignment checks negative toe and adjustments • Not a directional control angle • What effect does • Toe is a critical tire wear loading the truck angle that commonly have on caster? causes feathered tire tread wear 1 AUMT 1316 - Wheel Alignment 11/15/11 Steering and Suspension Steering and Suspension SAI and Included Angle Scrub Radius • SAI - Steering Axis • Scrub radius is the Inclination distance between • Angle between the the tread centerline steering knuckle and the point where pivot points and a projection of the true vertical steering axis angle • Included Angle would contact the • Sum of SAI and road surface camber Steering and Suspension Steering and Suspension Scrub Radius & Wheel Offset Toe Out On Turns • Toe out on turns is the difference in turning angles between the two front tires measured at a specific turning angle • Customers concerns about toe out on turns are usually related to tire squeal during low speed parking maneuvers • Improper toe out on turns is commonly caused by bent or damaged steering linkage and/or steering knuckles Steering and Suspension Steering and Suspension Thrust Angle Suspension System Service • Thrust angle is the • Alignments are often considered part of routine difference between vehicle maintenance the centerline of • A vehicle’s alignment should the vehicle and the always be checked and adjusted after performing thrustline of the any steering or suspension rear axle system service that could impact alignment angles • Negative - rear • Proper wheel alignment wheels point left affects vehicle handling, • Positive - rear control, ride quality and tire wheels point right life 2 AUMT 1316 - Wheel Alignment 11/15/11 Steering and Suspension Steering and Suspension Alignment Pre-Checks Tire Inspection • Tire pressure and • Check and adjust tire condition pressure to the vehicle manufacturer’s • Evidence of recent specifications collision damage • Inspect the tires for • Ride height abnormal wear such as • Wheel bearings • Center wear • Wear on both outer • Steering linkage edges • Suspension • Wear on one outer edge • Feathering components • Cupping or damage Steering and Suspension Steering and Suspension Bearing Adjustment Inspection Steering Linkage Inspection • Wheel bearings • Steering linkage should should be inspected be inspected for for proper excessive wear or damage adjustment or • Attempt to rock the tire excessive wear from left to right • Attempt to rock the • Carefully inspect the tire from top to linkage for evidence of bottom damage Steering and Suspension Steering and Suspension Suspension Inspection Types of Alignments • Inspect all bushings for • Center line alignment evidence of damage, • The vehicle’s front wheels cracking and wear are aligned to the vehicle’s center line • Inspect control arms, springs, ball joints, etc. • Thrust angle alignment • The vehicle’s front wheels for evidence of damage are aligned to match the and wear rear wheel’s thrust angle • Inspect shock • Four wheel alignment absorbers and struts for • All four wheels are aligned leakage and damage to the vehicle’s center line 3 AUMT 1316 - Wheel Alignment 11/15/11 Steering and Suspension Steering and Suspension Alignment Procedure Alignment Adjustments • Perform alignment pre- • Compare the alignment checks specifications to the • Set up the alignment vehicle’s actual settings computer as per the and adjust in the equipment following order manufacturer’s instructions • Rear camber • Mount and compensate • Rear toe the alignment sensor • Front caster heads • Front camber • Measure caster • Front toe Steering and Suspension Steering and Suspension Camber and Caster Adjustment Control Arm Shims • Camber is adjusted • Adding shims between the control arm and by moving the top of frame as shown moves the tire inward or the upper ball joint outward inward • Caster is adjusted • Changing the shim pack dimensions allows the by moving the upper technician to change steering pivot point caster and camber forward or backward • Some vehicles use shims to move the control arm outward Steering and Suspension Steering and Suspension Moveable MacPherson Strut Adjustable Strut Rod • Elongated strut • Change strut rod length mounting holes may moves the lower ball allow the strut to be joint to be shifted forward moved to change caster and/or camber and rearward • Some vehicles require • Moving the lower ball you to rotate the strut in joint forward increases mount holes to make caster changes in caster and/ or camber 4 AUMT 1316 - Wheel Alignment 11/15/11 Steering and Suspension Steering and Suspension Control Arm Cams Toe Adjustment • Eccentric cams allow • Toe is adjusted to the technician to move set the tires parallel the upper ball joint in to one another while and out the vehicle is • Moving both eccentrics equally changes only moving camber • Toe is adjusted by • Moving one cam in and increasing or the other cam out an decreasing tie rod equal amount changes length only caster Steering and Suspension Toe Adjustment Procedure • Set the steering wheel straight ahead and lock the wheel • Parallelogram • Loosen the clamps • Rotate the adjuster sleeve • Tighten the clamps • Rack and pinion • Loosen the tie rod end lock nut • Rotate tie rod • Tighten tie rod end lock nut 5 .