It depends more on the width of the rims, the offset, and the backspace rather than the diameter.
Stock 16" rims with 215x85 tires on them are 30" in diameter. 18" wheels with tires that approximate that diameter or less will surely clear.
1950 Chevrolet 3100 (Ol' Roy)
1939 Packard Standard Eight Coupe (The Phantom) | 1956 Cadillac Coupe de Ville (The Bismarck) | 1964 Ford Galaxie 500 coupe |1966 Ford Mustang (Little Red) | 1969 Pontiac GTO (The Dishpit) I 1979 Ford F-100 | 1976 Ford F-150 (Big Red) | 1995 Ford F-150 (Newt)