Jim, thanks for the info on how easily the drum should slide on.Len, you could be right that the front hubs are hub piloted with stud piloted studs. Both the drive and tag axles had hub piloted hubs with hub piloted studs and nuts, but with stud piloted wheels when we got the bus. That allowed the wheels to be off center in any direction and the ride was not smooth as a result. Those were changed to stud piloted hubs and studs from an MCI 9 that a friend was parting out. Since the front axle has stud piloted studs I didn't change those hubs. Even if the front hubs were originally hub piloted they still work as stud piloted with stud piloted studs. The flange that the hub piloted wheels ride on is not the problem. As you point out the hole in a stud piloted wheel is larger than that of a hub piloted wheel. The problem I have is that the outside of the hub flange that the inside ledge of the drum sits on is enlarged at every stud location. The bore of the drum inside the stud holes doesn't rest on the hub flange, there is at least a 1/2" clearance there. Nor are the stud holes in the drum tight fitting, some clearance there too. I hope I have explained the situation adequately, if not ask more questions.I appreciate all the thoughts that have been offered. Thanks, Sam