Tofind out if you need an alignment, first check each tire and look for uneven wearpatterns. The problem with this method, however, is that if you can see a wear patternlike the ones listed below, it may be too late to save that tire. This is why it is a goodidea to have your alignment checked periodically.
At each tire, take a coin and insert it in the tread at the inside, center and outside.
- If the tread is deeper on the edges than in the center, the tire is over inflated.
- If the tread is deeper in the center than the edges, the tire is under inflated.
- If the tread is deeper on one side than the other, have your wheel alignment checked soon.
- Run your hand back and forth across the tread, being careful not to cut yourself on any debris or exposed steel belt wire. If the tread is smooth in one direction, but jagged in the other you have what is called a "saw-tooth" wear pattern which is caused by a toe-in problem. Have the alignment checked as soon as possible as this condition causes rapid tire wear.
The first two conditions do not call for a wheel alignmentbut the second two do. If these wear patterns are pronounced, you should replace the tiresor move them to the rear before aligning the car. Ask your alignment specialist to besure.
Another indication of an out-of-alignment condition is a car that continuously driftsor pulls to one side of the road when you let go of the wheel. A car that is hard to keepin a straight line without constant steering corrections is also a candidate. Theseconditions may or may not also contribute to premature tire wear.
A wheel alignment cannot be done on a car with loose orworn front end parts. The technician will first check for worn parts and inform you of anyproblems before beginning the alignment.
The best type of wheel alignment is afour wheel alignment. Many cars today have adjustable rearalignment settings, but even for cars without adjustments in the rear, a four wheelalignment will allow the technician to identify any rear tracking problems and compensatefor them with adjustments to the front.
source:Wheel Alignment and* Wheel Balancing | CarParts.com