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Wheel Balance and Alignment
Keeping the front wheels on the ground and running true are the two most important functions of the front suspension system. One essential is wheel balance; the other is steering alignment. Wheel balance is controlled by the minimum radial and lateral run-out of the wheel rim, combined with a tire and tube assembly, mounted true on the rim and checked after fitting. Wheel BalanceOut of balance wheels are a common cause of uneven tread wear. The whole wheel unit - tire, rim and drum or disc - must be in balance, both statically and dynamically for best performance results. Dynamic unbalance can only be detected when the wheel assembly is rotating. Static unbalance maybe detected when the assembly is rotating and/or stationary. Static unbalance is usually felt as a vertical shake or fast vibration at speeds over 70km/hr. The whole vehicle or parts of its structure can be affected. Commons causes of static unbalance are heavy or light tread joins, or a flat spot worn by locked wheel skidding.
Why Wheel Alignment is ImportantWhen the front wheels of a vehicle are correctly aligned, they will roll without dragging or slipping and with a minimum of steering effort. Tires wear evenly and less strain is placed on front suspension parts. All this contributes to greater driving safety. Five angles are involved in proper wheel alignment: Caster, camber, toe-in, toe-out on turns and steering axis inclination. Actually, six measurements are involved, since most manufacturers specify the checking of front suspension height before making any adjustments. Caster, camber, toe-out on turns and steering inclination are measured in degrees and minutes: Toe-in and suspension height (some models) are adjustable; toe-out on turns and steering axis inclination are factory set and non-adjustable. On some vehicles, caster and camber are not adjustable.
Toe-InThe wheels on the same axle are closer together in the front than they are in the rear. When toe-in is excessive, the tire wear shows feather edges. Toe-OutThe wheels on the same axle are closer together in the rear than they are in the front. Tire wear shows feathered edges. |
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