Having your car's wheels aligned is an important part of vehicle maintenance that you should have done periodically because it basically makes your car more efficient. The benefits of having your wheels aligned are many, but you will find you get more even tire wear and better fuel economy with well aligned wheels, as well as a more pleasont driving experience because you car wont pull to the left or right; definitely an advantage on long drives! The difference between driving a car with poor wheel alignment and a car with good wheel alignment is like night and day. Don't confuse wheel alignment with wheel balancing - they are two different maintenance activities on your vehicle - both important, but different.
What is wheel alignment – in short is the process of adjusting all the angles of the wheels on your car so that they are parallel to each other and perpendicular to the ground. It sounds obvious, but if you have a car with one wheel pointing slightly left while all others are pointing forward, you are basically fighting against yourself while driving because 1 wheel is trying to make the car go left while the rest of them are making the car go straight. On some fixed cars with a solid fixed back axle, we only need to worry about wheel alignment on the front axle. Of course, we need to make sure that the front wheel are directly in front of the rear wheels to make sure that the car doesn't dog track (the back or rear of the car offset from the front), but on these types of cars, if this is not the case, the whole rear axle would need to be repositioned. On cars with four wheel independent suspension or on vehicles that have front wheel drive and adjustable rear suspension, we must carry out four wheel alignment.
The camber angle is defined as the angle of the wheel viewed from the front of the car. We express camber in degrees and we use negative and positive - negative camber tells us that the top of the tire leans towards the vehicle and positive when it leans away from the car. In general, camber can be set to match your driving style - someone who drives fast and corners hard will do better with a negative camber because it will give better grip through the corners. Of course doing this creates "camber thrust" so if for example one wheel goes over an oil slick, the other tire would push the car towards the tire that has lost grip. This can make the car feel more twitch to drive. Getting your camber right for your driving style will help keep your tread wear balanced. Notice for example the camber on a Forumla 1 car - these are set to help drivers corner faster.
Caster is the angle that the steering pivot makes when the vehicle is viewed from the side. Angled towards the front of the car is negative caster and angled towards the back of the car is positive camber. It is usually measured as a line between the steering systems upper and lower pivot points (for example the upper and lower ball joints on wishbone suspension). The caster of your vehicle will affect your steering effort. Positive caster makes it harder to steer a car (especially if there is no power steering), but it improves high speed performance and straight line tracking.
Toe In and Toe Out
Now that we have dealt with individual wheels, we have to make sure that the wheels are aligned in relation to each other. If the wheels point slightly towards each other, then we call this “positive toe” (imagine someone who is pigeon toed or think of it like in skiing when you have a snow plow position to slow yourself going downhill). Wheels that point away from each other would be called “negative toe” or toed out. It's pretty easy to see how these two alignments will wear your tyres - excessive toe in will wear the outside of the tyre down more while excessive toe out will wear down the inside of your tyres more. We ideally want the wheels to be parallel to each other for optimum driving. Toe is always adjustable in front wheels and on some cars, back wheels as well.
I hope the basics of wheel alignment make some sense to you and encourage everyone to get their wheels aligned periodically. You can buy a variety of tools to check and align your wheels yourself. All readily available on the internet. They are relatively easy to use and if you are fairly competant with your car, you should be able to do the alignments yourself. If you aren't comfortable taking on the task yourself, then check with your mechanic or garage if they do wheel alignment as part of your car's regular servicing or search for a wheel alignment specialist near you on the internet. Keeping your wheels aligned will increase your tire's lifespan, make driving your car easier and help reduce fuel consumption so it reall is worth having done.