Ha! I had to read the first post twice before I picked up on "lug bolts" like my Fiat has. Citreon used 3 on a bunch of their stuff but heck, so does my Snapper rider... wheels never fell off of any of my stuff so while I don't necessarily like it, they all seem to work.
To answer the OP though, my motorcycle trailer is 4x4.5, 2k axle 12" rim. Dad's old Dilly tilt boat trailer with a 4x4.5 wheel was an 8" rim if I remember right. Most of my boat trailers are/were 5x4.5 bolt circle in 13", 14", and 15" wheel sizes.