does anyone have 18" rims on there contour's or mystiques? or, does anyone know if they will fit, if so whats the best tire size to go....thanks

2000 mystique zetec. CTA intake, jbl muffler.
audio:4 infinity kappa 5*7's. 4 chrome tweets. 2 12" kenwood subwoofers, 1000 wat rockwood amp.jvc deck head unit.custom desgined trunk. no rattle...