I thought I'd share a very nice link that translates a lot about the mystery of wheels and tires

http://www.chris-longhurst.com/carbibles/index.html?menu.html&tyre_bible.html

also as an FYI I bought rims from a Mazda APV mini-van and they are a 5x112mm bolt circle though I have to open the stud holes to 14mm, I'll get some pics once thats done and they are mounted..

they are 15Jx 51/2 rims came with winter tread tires of 215R/65/15  (rated @ 1510lbs max inflation 44#'s). 
they wre on a similiarly heavy mazda 4wd van.