235 width tire on 74 Valiant sedan?

I had 235-60R14's on 14x7's with a 3 1/2" backspace. They didn't rub on those wheels, but the wider wheel may cause issues. I have 245-40R18's on the back now, mounted on an 18x8 with 4 1/2" backspace and they don't rub inside or outside.