Woke up this morning and my rear passenger side tire was completely flat. Got a can of Fix-A-Flat and was able to inflate it enough to get to a tire shop. They looked at it and saw that it had a huge gash from a piece of metal that went through the tire and inner tube. The guy said it would be ok if I just replaced that one tire. I have about 15k miles on the Q7... tread seems ok on the other three. What do you guys think about just replacing the one rear passenger side tire?