Google the question and found several answers.
>check aligment once a year. check more often with high mileage or with suspension >damage. The "once a year" or "once every 7,500 mile" alignment checks are nonsense. Many dealers and service garages recommend and perform alignments far more often than is necessary for most vehicles. Performing a proper, 4-wheel alignment is an expensive service item ($80-150 or more) that should only rarely turn up a problem that couldn't be diagnosed by less expensive means like observing tire wear.
-- For vehicles with 4-wheel independent suspensions (many vehicles nowadays) alignment checks at 24,000 miles or "major" service intervals (typically 30,000 miles apart) are a good idea.
-- For vehicles with "dead axle" rear ends (many subcompact, front-wheel drive cars) or rear-wheel drive vehicles with solid axle housings (like pickup trucks), you may not need an alignment in the lifetime of the vehicle. Getting an alignment check when you install new tires may be a good idea if you're especially careful or if tires for your vehicle are especially expensive.
-- DO get alignment checked if any of the following should happen:
- Tires show unusually rapid wear or unusual wear patterns like cupping of tread, wear on one side of tire, imbalanced wear (one tire versus other tire on same axle), etc.
- After an accident that may have involved the axles, wheels or chassis/frame of the vehicle, or after hitting an object like a curb, or an unusually deep pothole at speed.
- If vehicle begins "pulling" to one side or becomes more prone to "wandering" (requires frequent steering corrections to go straight down the road).
- After some kinds of suspension or steering repairs.