Mine came with 12 inch rims and three new 155/80R car tires. The over all diameter is 22 inchs. I think trailer tires are about 3/4 inch smaller.
Overall the height has me worried. The previous owner had a leaf spring suspension that was about 3 inchs narrower then it should have been and riding real high. Someone following me home said it lifted a tire off the ground pulling out of the storage area I picked it up at. It did have the entire interior and floor removed so the center of gravity would have been high anyway. I lowered it 3 inches when it was switched back to torsion axles. The frame is now 16 inches above the ground just in front of the wheel well. Just guessing at possible over travel on a big bump I was afraid to go any lower and risk the tire hitting the thin aluminum wheel well. Later I found this thread:
http://www.thesamba.com/vw/forum/viewtopic.php?t=283248
For now I'm going to see how these car tires do since they are paid for. May end up switching to trailer tires and lower it some more. If I can lay my hands on some 10 inch aluminum wheels that fit and are cheap even better. I would be less worried about that light weight slab sided thing if it were closer to the ground.
Jerry