Check the condition of the chain/lift device that secures the spare tire especially if you haven't used the spare in a while. The chain in my '98 has deteriorated to a point where I really think it needs replacing. A couple of the links are about half the thickness of the original. I emailed Nissan a brief report but somehow I can't see them getting too excited about it. Anyway, it's out there.
Beware and don't get too close when following older models. Pathfinders that is!