I'm converting an old Raleigh grand prix, and I just discovered that the headset fixed cups are loose, as though the headset was adjusted too loose and the bike was ridden hard for many years, which it probably was. The cups just slip in and out of the head tube and even slop around a bit.
This is a budget job on a foul-weather beater, so I'm not expecting the usual tolerances, but I do have certain standards. I don't see any reason why I can't shim the cups to get a better fit, but I'm wondering what would be the best metal for the shims. Both the frame and HS are steel, the latter chromed. I have steel, aluminum and brass shim stock readily available.