When it comes to wheel alignment, a lot of us think we just "know" when our car needs it and when it doesn't. Wrong.

Brian Watkins, a veteran Goodyear automotive expert with County Line Car Care, Spring Hill, FL, spoke yesterday about some of the common misperceptions... and he offers advice that can help you be sure you're getting what you're paying for.

Cost: For most passenger vehicles across the country, wheel alignments can range on average from $59.99 at the discount tire shops to about $89.99 at car dealerships. For exotic cars, obviously it can be a lot more.

"Most reputable shops will take you out there and show you while the car is on the alignment rack, if not on paper, give you a printout both before and after the alignment was done. They'll give you the paper to show you where it was -- where the alignment was needed, the adjustments that they made, and then a final printout to show you that everything is back to the manufacturer specifications for your vehicle.

If they can't do that they can at least bring you out to the shop and show you on the computer screen that the car is in alignment before they pull it out.

How often should motorists be thinking about wheel alignment?

For most vehicles it's once a year. The importance of doing the alignment is that if the car and the wheels are not in line with each other it's going to create forces pushing off each other. Those forces can internally decrease your fuel economy; they can prematurely wear out your tires... and most of the time people are getting the alignment done when they are buying new tires. That's the best time to do it.

At most reputable tire stores, if you're buying four tires from them, they'll at least check your alignment free of charge. They'll take the time to take the measurements, put it on the alignment rack and let you know if you do need an alignment or you don't.

Some people say they know when their car needs wheel alignment... is that possible? No, unless thy're inspecting their tires on a regular basis. One of the symptoms is when the car is "pulling". If your car pulls, the majority of the time it's because you need wheel alignment, but it can be a symptom of other things as well. Drivers certainly can feel that. But uneven tire pressure or faulty brakes can cause a pull too.

You can have a car that drives perfectly straight down the road and it can severely need alignment. That's because if the two front wheels are toed in evenly, they're going to be pushing off each other equally, so the car will still drive straight down the road but can still cause tire wear... A lot of people think 'my car drives straight, I don't need alignment'... That's why wear patterns are so important.

Wear Patterns: When someone is doing their tire rotations they should make sure they're checking the wear patterns too. Most people will rotate their tires with every other oil change, or every oil hange depending on the frequency. At least every 6,000 miles the tires should be rotated and at that point, also checked for tire wear.

That way if you do notice any uneven wear starting to develop, you can rectify it by doing the alignment before further damage is done to the tires.

Depending on how severe the alignment is, you can take an 80,000 mile tire and wear it out in 40,000 miles. Obviously if you have an alignment that is severely out, you can wear the tires out in a couple thousand miles.

Watkins says another way to understand wheel alignment is to think about skiing down a mountain. The way you slow yourself down is to point your skis in toward each other. That creates friction between the skis and that, in turn, slows you down. It's the same thing with a wheel alignment. If your tires are 'toed' in or 'toed' out, it's going to create enough friction to the point where it will begin holding back the vehicle, which is not only going to wear the tires but rob you of fuel economy and handling as well.

In his 25 years of automotive experience in tires and alignments Watkins says he's seen just about everything. "For some exotic cars, they actually require that you have a full tank of gas when doing an alignment because the weight inside the vehicle changes some of the angles of the alignment. Some vehicles even require weights of 150 to 200 pounds put into each seat when doing the alignment. That's because when you perform an alignment on a car without any passengers in it, it's different from when one person can gets into the car. The angles change as the suspension of the car are lowered or raised.

I had a woman who came into my shop and asked me to perform an alignment on her vehicle, but the stipulation was that she needed to be in the car when we performed the alignment because she knew she wasn't going to get a proper alignment done if she was out of the vehicle. This woman weighed approximately 400 pounds and that's a significant amount of weight on one side of the vehicle.

A lot of the cars nowadays not only have adjustments on the front, they have them on the rear too. Newer cars have independent rear suspension and there are adjustments back there that some technicians might overlook if they're unfamiliar with it. They'll just do a front-end alignment.

The best thing to do is get the readings on both front end and rear alignment specs and make sure that everything is adjusted back to spec.

Watkins noted that some years ago when he was visiting the NY Dept of Motor Vehicles, they had TV monitors broadcasting automotive information and they reported a DMV study where they randomly inspected miscellaneous cars off the road. They found that 9 out of 10 cars needed a wheel alignment and the drivers weren't even aware of it.

He added that bumps and potholes are just about everywhere, but most of the colder northern states are more prone to it. You can hit bumps just by pulling in and out of your driveway every day... Over time, even that can be enough disturbance to cause the alignment to go out.