How to check that your wheels need aligning?
Toe is the fore-and-aft difference in tire distance. Most vehicles are slightly toe-in for a lighter steering feel and to keep a slight pre-load on wheel bearings.
Camber measures tire lean. Camber isn't adjustable on many front-wheel-drive cars, and an out-of-spec measurement usually indicates bent or worn part(s) on these vehicles.
Irregular tread wear signals alignment problems. A saw-tooth pattern indicates a toe problem, and bevelled wear points to camber problems.
The benefits of having your wheels aligned are improved stability and handling of your vehicle and increased and improved safety.