There are some things that you need to be aware of when it comes to Wheel Alignments. For many years I worked as a wheel alignment technician doing car, light truck and heavy truck wheel alignments.
Wheel alignments are a specialized job and I recommend that when you are considering getting your vehicle aligned that you try and find a wheel alignment specialist rather than just your local tire shop unless you are sure that they have an experienced and competent technician as well as up to date and calibrated equipment.
A wheel alignment from technical perspective consists of three main areas, the most common of which is Toe in and Toe out.
Toe
In many of today's modern vehicles this is sometimes the only part of wheel alignment that can be easily adjusted. Toe is the most common form of tire wear. In the diagram below this is a birds eye view and shows an example of toe in if the tires were tending the way of the arrows.
toe : birds eye view
Camber
Camber is if you are looking at the wheels front on amount of negative or positve degrees that they are sitting at. Most race cars for example have quite a bit of negative camber as this can assist when cornering at very high speeds. On many cars this is not easily adjustable however it is always measured and any issues should be pointed out to you.
camber: front on viewCastor
The last measurement in regards to a basic wheel alignment is castor. Castor is in laymans terms whether one wheel is physically further ahead or behind the other. Often for example if you crash into a kurb this could push the left hand side castor angle back behind the right hand side. Again not actually adjustable in many of todays cars however should be measured and issues reported to you.
You should ask for and receive a print out of the wheel alignment before and after specifications and report. Check they have the right vehicle details and that any variations from the specifications have been either addressed or explained. A common misunderstanding by vehicle owners is that all parts of a wheel alignment can be adjusted on every car and this is simply not the case.
Camber of the Road
Another thing to bear in mind is that most roads have a camber of their own heading sloping towards the edge of the road. Most roads are not flat so expecting your car to drive in a perfectly straight line is not always a reasonable explanation. In New Zealand we drive on the left hand side of the road and most cars should and will pull slightly to the left. This is actually very safe because it reduces the chance of drifting into oncoming traffic if the driver is not paying attention.
If you have any questions you are welcome to ask them.