Tires: Tire Pressure, tandem axles, gross vehicle weight

Question
I have 16' Lamar dump bed trailer. I can't find and placard. It has 10.00lb tandem axles.  It came with 7.50/16' nylon tires, 10ply.  Although I realize much depends on the load I am carrying so let's say I carry 4 tons.  I am running 65psi but I am insecure about that pressure.  Any place I can find a table of pressures or am I ok with what I am putting in the tires?

Answer
Albert,

Let's assume that the 2 10,000# axles are needed as well as 4 tires, whose load carrying capacity is also 20,000 # (5,000 # each)

A 7.50-16 Load Range E has a load carrying capacity of 2755# at 80 psi.  So 4 tires would carry 11,020# as singles.

This doesn't quite add up.  Is it possible that the tires are dualled and there are 8 of them?  That would mean the tire could handle as much as 2470# at 80 psi or the Gross Vehicle Weight (GVW) would be 21,920# (limited by the tires), but since the axles are 10,000 # axles, then the GVW would be 20,000.

Unfortunately, these tables aren't generally published on the internet,  particularly for this size - you have to buy the book at about $60.00.  But if you have any more questions I'd be happy to answer them.