Ok, this weekend we took a closer look at the tires. Both front and rear are 5-lugs. We cleaned them off and confirmed: They're Motor wheels.

We took some measurements and wrote down some numbers we saw on them. Maybe somebody knows what the numbers all mean.

First, the hub measured 6". Distance between each lug, going around the hub, measured 4 5/8.

On the wheel was stamped a sequence of numbers:
83110 4 3/4 8 48

I don't know what the 83110 means. I wonder if the 4 3/4 was the distance between lugs, and we just measured badly.

Then the 8? That the distance from the hub to the edge of the wheel: 8", so maybe that's what this means?

and 48? maybe the year the rim was made? its the year of the truck.

Anybody got any ideas?