I have some 18-inch rims on my Acura Legend. My tire size is 225x40x18. Since I put them on my car, the back end is rubbing when I hit bumps or have weight in the car. Is my tire size too big or is it the offset of the rim? If it is due to the offset of the rim, and I purchase new rims with the appropriate offset for my car, will ANY 18 inch rim fit on my tires since they are 18inch in diameter or will I have to buy new tires also?