Truck Alignment Diagnosis

ALIGNMENTDEFINITION: The process whereby the vehicle and all the tires are traveling in the same direction.Plays a significant role inTire performanceReducing Tire CostsVehicle handlingDriver controlImproving fuel economyComponent life

8 Components of AlignmentCASTERCAMBERKING PIN INCLINATIONTOEACKERMAN ANGLETURNING RADIUSAXLE PARALLELISM (thrust and scrub)AXLE SETBACK

AXLE MISALIGNMENT1. Drive axle misalignment most frequent2. Trailer misalignment 2nd most frequent3. Steer axle misalignment least frequent123

CASTER- Forward or backward tilt of the steering axis as viewed from the sideNecessary to provide self aligning forces on steer tiresAssists in turning wheels to straight ahead position when going around cornerStabilizes vehicle when: braking acceleratingGives directional stabilityDecrease susceptibility to crosswindsHelps offset effects of road crown

CASTER PROBLEMSINSUFFICIENT CASTER Reduces stability Vehicle wandersEXCESSIVE CASTER Increases steering effort Can cause a shimmy Can cause shoulder wear on tires in city operationINCORRECT CASTER CAUSED BY: Incorrect shims or installed improperly Sagging springs Worn shackles and bushings Twisted axle

CAMBER- INWARD OR OUTWARD TILT OF THE WHEELS WHEN VIEWED FROM THE FRONT OF THE VEHICLENECESSARY TO :REDUCE SIDE THRUSTCOMPENSATE FOR WEAR ON STEERING KNUCKLECOMPENSATE FOR WEAR ON WHEEL BEARINGSSHIFT WEIGHT TO INNER WHEEL BEARINGBUILT INTO AXLES - NON ADJUSTABLETRUCK WILL LEAD TO THE SIDE WITH MOST POSITIVE CAMBER.

INCORRECT CAMBERINCORRECT CAMBER CAN CAUSE:EXCESSIVE TIRE WEARWANDER (PULLS TO SIDE WITH MOST POSITIVE CAMBER)HARD STEERINGEXCESSIVE TIRE HEAT

KINGPIN INCLINATION-The amount, in degrees, that the top of the kingpin inclines away from the vertical as viewing from the front of the truck.Kingpin Inclination working together with camber angle are called Included Angle. Included Angle puts the approximate center of the tire tread in contact with the road. Kingpin Inclination has the effect of reducing steering effort and improves directional stability.

Preferred tolerance is 1 degree from side to side. Can be used to help determine if an axle or spindle is bent.

TOE - The inward or outward pointing of the wheels when viewed from the top of the vehicle.Necessary to compensate for tendency of wheels to deflect rearward when loaded or in motion.Goal - zero toe when loaded and in motionIncorrect toe shows up as feathering of tread on both ends of axle - greatest tire wear problemPreferred Specs. For radial tires are .03 to .07 (1/32 to 1/16) toe-in.

A feather or saw tooth edge pointing inward will indicate excessive toe-in A feather or saw tooth edge pointing outward will indicate a toe-out problem.

ACKERMAN ANGLE (TOE OUT ON TURNS)

CHECKING ACKERMAN ANGLEMeasure WT (width of tires) and WB (wheel base)Read intersection of WT and WBTurn outside wheel to 20 degrees, and read turn table dial on opposite side to verify proper toe out on turns

Preferred Tolerance +/- 2 deg. for Over the road and +/- 1 deg. For cityNote: readings from left to right should be within 1 degree.Correction: replace ackerman arm

AXLE SETBACK

AXLE PARALLELISM - All axles should be perpendicular to the frame and parallel with each other(Steer, drive, and trailer)The rear axles are what determine the direction the vehicle is going to travel.Rear axle misalignment result in excessive tire wear on front and rear axles.

Thrust Angle - axles not perpendicular to frame but are parallel to each other.Tends to push vehicle off courseDriver feels pullingSteer axle tires feather in same directionDrive tires show I/W

Scrub Angle - Axles NOT perpendicular to the frame and not parallel to each other.Constant pull in one directionNeed to continually steer against pullDrives scrub as vehicle is forced to go straightAlso affects steer tires

Trailer Thrust will cause Dog TrackingEasily visible in tractor mirrorsEffects all tires on tractor and trailerVehicle wanders

AXLE PARALLELISM IS CORRECTABLESOURCES:Uneven axle springsBroken leaf springsWorn springsLoose U boltsBent frameAdjustment of torque rods /axlesWorn torque rod bushings

DRAG LINK ANGLEParallel to mid-point of spring mounting +/- 15 degrees upward or downward

EFFECT: Bump steer or directional change - steering stability - no set wear pattern

Four Damage ConditionsTwistSide SwaySagDiamond

Side SwayKenworth says if the frame is bent laterally enough to cause tire wear and handling issues then the frame rails must be replaced.If someone were to try and correct the frame then Side Sway should be corrected first.

SagKenworth says that if bent, Frame rails should be replaced- not repaired.If someone were trying to correcting a bent frame rail then Sag would be corrected after side sway and before a Twist or Diamond

TwistTwist is generally caused by bent cross members. Locate the strongest Cross members (from back of cab to back of frame) - they are the ones that usually hold in the twistTwist normally will show up in the front because of lighter springs - but is actually held in the back.

DiamondCaused by bent Cross members.Occurs most often today when a vehicle is hit directly on the frame rail front or rear or most likely if the vehicle has been towed or pulled on one frame rail.

TRUCK ALIGNMENTRENTON ASSEMBLYPLANT

ALLWHEELALIGNMENT

CHECK RIDE HEIGHT

ZERO TO FRAME

CHECK PINION ANGLE

LATERAL OFFSET

SWAY BAR BUSHING GAP

CHECK THRUST BUSHINGS

CHECK VEHICLE LEAN

INSTALL HEADS

RUNOUT COMPENSATION

CHECK THRUST ANGLE

PERFORM AXLE SWEEP

CENTER WHEELS AND SET TOE-IN

SET UP TO CHECK REAR AXLE SCRUB

SCRUB ANGLE

CHECK TURNING RADIUS

SET AXLE STOPS

ADJUST BRAKES

CHECK STEEING SHAFT ALIGNMENT