[thstone]

Yearly for a car that goes to the race track sounds reasonable. If you go off course into the weeds/gravel or hit something, then it might be time to have it re-checked.

Heavy wear on the outside 1/3 of the tire might also mean that you need more negative camber to keep the tire flat when the shocks compress in turns. The tradeoff is that with more negative camber the inside 1/3 of the tire will wear faster on the street.