I had a puncture yesterday, had to put spare on at the nearest garage, it was new and never been used.
As I had to wait for the tyre to come in, I drove home and driving along it was a bit bumpy, I checked there was enough air in it, and there was.
Anyway when I went to get the new tyre on today (PS4), I looked at the spare when off the car and the bead on the tyre hadn't properly clicked into the steel rim at the rear, which must of been from when it was new, the guys said they had never seen it before, they had to put 150psi in it to make it click out flat on the rim and be secure
luckily I didn't have to drive far, but it could of been a different story.
moral of this story, check your spares!