The second major system type is the disc wheel system. Here, the rim is permanently welded to a wheel with a disc in the center containing a mounting face with a bolt hole circle. This wheel is bolted onto the vehicle with studs that are inserted through holes in the hub, brake drum and wheel and fastened with lug nuts. When a tire is changed, the whole wheel is removed from the vehicle and then the tire is removed from the rim.
There are two types of disc wheels -- hub-piloted and stud-piloted. Hub-piloted disc wheels are designed to center on the hub at the center hole of the wheel. The wheel center hole locates the wheel on pilots built into the hub. Hub-piloted wheels are used with two-piece flange nuts which contact the disc face around the bolt hole. Only one nut on each stud is used to fasten single or dual wheels to a vehicle.
Stud-piloted disc wheels are designed to be centered by the nuts on the studs. The seating action of the ball seat nuts in the ball seat bolt holes centers the wheels. Stud-piloted dual wheels require inner and outer cap nuts. Steer/single wheels are attached with outer cap nuts only. This system is 30 or 40 years older than the hub-piloted system.
Rims for spoke wheels are generally referred to as "Daytons" since Dayton was a big manufacturer of spoke wheel/demountable rim systems. Stud-piloted disc wheels are commonly referred to as "Budds" since The Budd Corp. was the first to come out with these wheels. You hear hub-piloted disc wheels called "Unimounts" which is what Motor Wheel called their wheel when they first introduced hub-piloted wheels in the early 1980s.
This has been a fascination for me since childhood. Every kind of large truck uses either Daytons or Budds. I must tell you-the Budd company must be INCREDIBLY rich from the patent on their design, since it's used in every kind of variation all over the world, on trucks and buses, large and small. You simply can't get away from it.
The Daytons seem to be relegated to mostly trucks-and in the United States, the only kind of bus that uses Dayton wheels are school buses. I have never seen Dayton wheels used on commercial buses in the U.S., and it is a big mystery to me as why this is. Does anyone know?
These two seem to be the industry standard. Most trucks use either one type or the other, although I've seen trucks that mix both-though more often than not, the Daytons usually end up being used in the rear, with Budd type wheels in the front.
Edited by Digital Man, 03 December 2006 - 10:57 AM.