Now should you get a two-wheel or four-wheel alignment? At any rate the  technician will put a sensor on each wheel. In a two-wheel alignment  rear toe and thrust angle is checked. Then all the adjustments are made  on the front wheels. This happens on cars that don't have rear wheel  adjustments, but can determine if there is something wrong with the back wheels.

In a four-wheel alignment the rear wheels are adjusted to specification  before any front wheel adjustments are made. In relation to the added  work, the four-wheel alignment does costs more. All vehicles should be  4-wheel aligned. Two-wheel alignments have become obsolete because they  align only the front wheels to the vehicle's centerline. A 2-wheel  alignment assumes the rear wheels are already aligned with the geometric centerline. Two-wheel alignments may save you a little money up front,  but your vehicle's handling and tire tread life will be compromised.

Now, before any wheel alignment is done, the car should be road tested so  the technician can see what the vehicle is doing. Then the front end  should be thoroughly inspected for worn, bent or broken parts. He should check that the tires and wheels match and that the tires pressures are  set correctly.

Older cars could have the camber, caster and toe adjusted. On most modern  cars, this is no longer true. On all cars toe is adjustable but front  McPherson struts set caster and camber. The theory is that as long as  these components are not bent or broken, the alignment will always be  set properly. Notice I said "in theory." In the real world, other things besides the struts can be thrown slightly out of adjustment causing the wheel to be thrown out of line. In cases such as this, some aftermarket manufacturers make kits that can be installed to allow caster and  camber adjustment.

How often should you have your wheels aligned? Some manufacturers recommend as little as 10,000 miles. Personally, I feel once a year is a good  interval between alignments. A yearly alignment can add thousands of  miles to your tires over the years. That's money in your pocket in tires not bought and extra fuel not burnt. Of course if you buy new tires,  that's an excellent time to have your wheels aligned.

For most standard American cars a wheel alignment will cost about $69.00.  There is usually an extra charge for vans, 4x4's or 4-wheel steer cars  and it takes about an hour to do.