Thanks for all the replies. I did check the tire pressure, they were all either over inflated or underinflated. The fronts are now 32psi, the rears 33psi. I checked the lug nuts and retightened them all. I don't remember what brand tires the new ones are. The old ones were stock tires. It's at pepboys right now. Just talking to the guy there, he thinks it might be a separated tire.