On Fri, 16 Jun 95 11:03:27 CDT Timothy D.F. Maddox said:
>Anyone know what the spare is supposed to keep 42 psi? (Bentley manual
>"lubrication and Maintenance" p. 19) I have never noticed this before and
>wondered what the reasoning is.

my thinking is that
(1) tires leaked air. period. so hopefully, by the time you needed the spare,
    it still had at least the required pressure still in it. hence, the need
    to check the spare BEFORE the trip. :)
(2) unless you have an air pump (and you ALL should have one in your bus!),
    it's a whole lot easier to bleed air FROM the spare than it was to blow
    air back INTO it! :)

leastwise, that's what i figured out in my own little brain.