I'm looking into replacing the 2" double rubber wheels on a 60 year old D. I bought a new set from Schaff but the stems are a larger diameter than the originals and the new sockets are square rather than round which would require removing some material from the underside of the legs. Is there a better solution available from another supplier that wouldn't require modifying the legs? Alternatively, I could replace the casters on the venue's older grand truck and use that. As it is the piano is difficult to move and it must traverse a very small threshold at the stage exit.
Did you check with SCHAFF to see if they had the round cups as an option? If you do modify the inset to fit the square cups, you'll also likely find the inset is too deep and the wheels bind on the leg. I did this recently ( well, before I fell) and had to make a 1/4" thick insert to build up the inside of the leg. Not too hard , used a lockset drill to cut it out and then drilled holes for screws and cup stem, worked ok. if you can find a supplier of the brass double casters like Pianoforte Supply used to carry, they work well, will be a round cup, and won't need an insert because the brass fittings are thicker. Two Ds were modified this way at Pianoforte Chicago before they were sold, worked fine. Hopefully you have a " Jack in the Box" or piano lifter so you can remove legs and install the new casters. I don't remember where the brass double wheel locking casters came from, but they were smaller than the really big ones now used on concert grands. You might want to get rid of that threshold if at all possible. Pianos don't hop well, but people keep trying.