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Correct wheel or tire alignment is essential to good handling capability of your vehicle and plays an important role in tire life. Misalignment and improper inflation (see tire pressure) are considered the two principal causes of premature tire wear. ...
Improper alignment can reduce a tire's life by more than 70%. The effect is so great, in some extreme cases, that a new set of tires can be completely worn out in a modest week-end trip.
Signs of incorrect tire alignment include vibration, shimmy or a tendency for the vehicle to wander, or pull to one side when driven at highway speeds.
If you notice, when you're driving on the highway that the vehicle starts edging to one side or the other rather than maintaining a straight line when you loosen your grip on the steering wheel for just a second, you likely have an alignment defect.
Things which cause misalignment include aggressive cornering, hard braking or bumping a curb.
Alignment involves adjusting the wheels to specifications set by the vehicle manufacturer so they track in a straight line. Mechanics often talk of a front-end alignment since the front wheels are more often the ones that become misaligned.
When a vehicle that is out of alignment is driven the tires to will wear unevenly, usually on an outer or inner edge (just one side). To avoid damaging your tires, and to make sure the alignment problem doesn't get worse, it's important to correct the situation as soon as possible.
When your mechanic does the alignment, several measurements are checked and adjusted if necessary. These include camber, caster, and toe.
Camber refers to the inward or outward tilt of the wheels. If the tops of the wheels angle in toward the vehicle, this is referred to as negative camber. If the tops angle away from the vehicle, it is a positive camber. When properly adjusted, the camber angle keeps the outside tires flat and stable on the ground during a turn.
An incorrect camber setting will result in improper handling and tires will wear out prematurely. If you have too much positive camber, your tires will wear on the outside. Too much negative camber will wear them on the inside. If there is too much of a difference between the camber settings on the front wheels, the vehicle will tend to pull sharply to one side.
Caster refers to the angle of the vertical axis of the wheel in relation to the steering connection. A high caster angle will produce greater stability at high speeds, but steering may be more difficult at low speed. A lower caster angle results in easier steering, but the vehicle may wander at higher speeds.
Caster is adjusted according to factory specifications on individual vehicles to arrive at the optimum balance -- achieving stability and control at both high and low speeds.
Properly adjusted caster allows the wheels to track in a straight line and prevents shimmy. The caster angle can often be best understood by looking at a typical shopping cart caster, as shown in the above figure.
When you push a shopping cart equipped with caster wheels, it tends to roll in a straight line because the wheels line up or trail behind the point of pull. The greater the trailing distance, the greater the tendency to roll straight. The caster setting on a vehicle is adjustable in order to increase or decrease the effective trail distance.
Toe refers to the front end of the wheel just as your own toes are at the front of your feet. Toe-in is a condition in which the front ends of two wheels on the same axle are angled slightly inward so that they are closer together than the heel ends. Toe-out refers to the opposite condition -- the toes of two wheels are angled slightly outward, so that they are farther apart than the heels. Severe toe-in or toe-out causes uneven and excessive wear so that one side of the tread wears out more quickly than the other .
Toe settings affect the handling of a vehicle in turns. Toe-in introduces Understeer going into a curve and may make the vehicle feel like the back end is trying to come around to the front end. Toe-out introduces Oversteer in a curve and makes the vehicle feel like it is "diving" into the turn too sharply.
If the tires have too much toe-in, the tread will be worn off, starting from the outside edges. If they are toed-out, the wear will start from the inside. This type of wear is called feathering and can be felt by running your fingers across the tread of the tire.
Each vehicle has factory specifications for camber, caster and toe which should be followed precisely. Improper alignment not only causes poor handling and premature tread wear, it also reduces fuel efficiency.
The alignment of your vehicle can be knocked out of adjustment from daily impacts such as potholes and railroad crossings or by more severe accidents. You might want to have your vehicle's alignment checked if:
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