There are three important services that an auto repair shop can do for your auto: balance the tires, align the wheels, and rotate the tires. The first two don't need attention that often; tire rotation needs to be done little more frequently.

Balancing:

• No matter how well a tire is made, it's probably going to need a little help to spin correctly--i.e., without wobbling. Generally a mechanic does this by attaching small weights to the wheel rim; this offsets any irregularities in tire or rim construction. Balancing can be done with the wheel on or off the vehicle, but most times it's taken off.

   

• When you first buy a tire and have it mounted, it should be balanced as well. As the years go by, and the tire wears down, it may need to be balanced again. A noticeable vibration in the vehicle is a good indication that a tire needs balancing (or something else is wrong--find out now!).

Wheel Alignment:

Picture a hoop around your waist, and imagine that it's a wheel and tire combo on an axle. If you can imagine the different ways that a hoop could shift position around your waist-- forwards, backwards and side-to-side--then you have an idea of how a wheel and tire can shift around on the end of your axle. Alignment makes sure that the wheels and tires are in the correct position in relation to your vehicle, and each other. This should be done when tires are bought and mounted on the vehicle.

• Camber, Caster and Toe are what need to be adjusted here. An auto manufacturer will specify precise reset values that the mechanic can look up and use to set your wheels up correctly.
• Due to better design and manufacturing, some vehicles stay in alignment better than others. But unless you're four-wheelin' on dirt roads, your vehicle will need to be aligned only once or twice a year. How do you know if the vehicle is out of alignment? Keep an eye on your tire tread: if the tread is wearing unevenly, take the vehicle in before the tire is seriously damaged. Another clue: while you're steering straight ahead, the vehicle has a tendency to veer to one side or the other. This may also be fixed with alignment work.