"Bruce L. Bergman" wrote:

....
Mount the spare on the outside - tongue, side, or underneath.
Murphy's Law says you'll only get a flat when the spare is buried
inside under a ton of loose crap, and it'll take you an extra hour to
dig for it - and then you have to put everything back.

A better place is to mount the spare on the inside of a swinging side
door. That way it's protected from the sun and thieves, but won't get
buried either.