Mrs. Hitbyatrain left me her car today, so that I could get the oil changed, and maybe put some new tires on. (I'm not all that vehicle-savvy, but I do know how to change my own oil and perform other kinds of minor maintenance--unfortunately, it's cold outside, and we live in an apartment complex that frowns upon changing your oil in the parking lot.) Anyway, she drives a Pontiac Grand Am, which is front wheel drive, so, without proper tire rotation, the front tires wear more quickly than the back tires. Like I said, it's my wife's car, so proper rotation hasn't happened (yes, that's probably my fault, too. ) Now, I've always understood that it's OK to just replace the two worn tires, usually by rotating the rear tires to the front and putting the new ones on the back. However, others have mentioned that we should just replace all four, becuase having two different sets of tires is somehow "unsafe." I don't buy the "unsafe" argument, especially if all four tires are the same size. But I've been wrong before (lots of times), and like I said, when it comes to cars, I can change the oil, and turn them on. Any thoughts?