The older rigs used split rims that most shops won't service. 16.5 rims are dangerous if you try to mount 16 tires on them. I was working a tire shop when a kid tried this. The tire exploded, sending tire and rim to the ceiling, bending a steel rafter before coming back don, He was lucky in that it blew him back out of harrm's way, but the tire machine was a mag machine with the rotating table, and it didn't fare so well, it was trashed entirely. The table was tilting, and oil leaked out from underneath. I currently have 16.5 aluminum rims on mine, but I will be replacing them when the tires are worn out. they came with the truck when I got it. The tires are the equivalent of running 245 75 r16's which is abaout an inch shorter than it is supposed to have. The speedo's accurate, got the ticket to prove it. It (speedo) must have been re geared to match the tires.