I got a flat tire but need to go somewhere tonight. My car, a 99 Firebird Trans Am, has 19" rims. I have an old tire that is exactly the same size as the ones on my car, but the rim is 18". I want to use this tire as a replacement for the back right wheel. Since the tires are the same size, I don't see why it would be a problem. But, will doing this mess up my car?