This site tells all about tire size, rim size, back spacing, and not rubbing tires on the duals.
http://www.accuridewheels.com/completeversion.pdf Rims larger than 22.5 inch are not as common, require tires that are too tall and wide to fit our AD trucks.
While tall tires make you go faster there is a limit as to what fits, and to the brakes you have to stop them. I have found that the 1.5 and 2 ton AD trucks will fit about a 39" tire, same as a 8.25X20 and 9R22.5, on the front but they rub the springs at hard turns. Most people don't mind this.
For the rear you won't find wheels larger than 22.5"X6" without having them made. Bolt pattern adapters are not available to switch from the small 10 lug to the large 10 lug used by almost all large trucks today. there physically is not enough room to easily make adapters, there is two much interference between the two bolt patterns to make it work safely. I believe 9R22.5 tires are as large as is recommended on the available 22.5"X6" wheels. 10 or 11R22.5 tires could probably be run in the rear if wheels could be found to fit. That is about as large as I would try and fit on our old trucks.
I have not mentioned the multi piece 20" wheels that they came with. Tires are available to fit the somewhat narrow rims to get about 40" diameter. With wider rims you may be able to run single 20" tires in the rear. The surplus military Michelin XL, XML, and XZL tires can be had relatively cheep and are 46", 52", and I think larger. Any larger single tire should fit the rear, only limited by the bed interference, depending on your bed, however special wheels would have to be made.
I think that 8.25X20 and 9R22.5 tires are as big as is practical for our 1.5 and 2 ton AD trucks.
Grigg
