I could be wrong, but from the pictures I have seen it looks like the rims are dexter "Dexstar rims'?
What I see online, they are rated for 65 psi and 2,040 load. But there should be a sticker or stamping on the rim for the max load and psi.
Here is a link to the rim that I referenced.
http://www.etrailer.com/Tires-and-Wh...r/AM20352.html