>In my case, the original light truck tires (4 ply, 6 ply rated), and
>the reinforced passenger tires were rated at about the same maximum load. 
> However, the light truck tires were rated for that load at 50 psi, and the 
>reinforced passenger tires at 40 psi.  (I don't remember the details about 

A real nasty I found with my '85 panel when newish.  The 4 original Conti
Transports were rated at 55PSI max, and I ran them at 44 rear, 38 front.
Got a flat on a long trip and pulled out the Conti Transport factory spare.
It went on the rear, and I checked at next gas station to find it was low,
36psi, so I put it up to 44.  Got another 50 miles, loud thumping started,
so I stopped/checked the wheel nuts, then drove on.  Still thumping, until
KER-BLAM.  The spare was the IDENTICAL Conti Transport, except rated at
35psi max!  They sure fooled me.  Only way to tell was the model number 77R
was just 77, and by the max psi on the shredded sidewalls.  Cheap of VW,
real cheap.  I will only buy tires that say 55PSI max or higher, the load
capacity means squat!  Tim