Dual wheels and tires are common on large vehicles that carry heavy loads. The hubs used are unique to the vehicle and require special wheels not used on ordinary trucks or cars.
I bought a dune buggy years ago and put very nice custom aluminum wheels on it that are 15 inches in diameter and 15 inches wide so I can use big tractor tires for the street and I can put big paddle tires on the wheels for sand.
Here is a picture of the wheels and paddle tires mounted on my buggy. The second wheel is held in place by bolting it to a hub I invented that is shown below.
The thin threaded rods were removed after the hub ends were welded on. So the outside wheel bolted on using the 5 holes you can see.
It has come to my attention that there are no sources for dually hubs for your everyday car or truck so this web site is for the purpose of showing you how I can make a hub that will work perfectly for YOUR vehicle.
Here is a picture of the inside of one of the wheels. You can see it has a flat plate to bolt onto the brake drum lug bolts. This made it very easy to design a hub for it. Note the air valve in the side. A channel was cut in the hub to avoid hitting that.
Here is a picture of the hub I designed.
I cannot resist showing the result in sand dunes!