The old style wheels have a tendency to leak in two places - where they are vulcanized to the center aluminum tube (that's why the newer versions have hubs) or the inflation valve.

Try taking an old inflation needle and fill it with silicone or glue. When it's dry, stick it in the inflation valve after you've fully inflated the wheel. That will usually stop that leak.

I used "Automotive Goop" and schmeared it all over the edge of the tire where it met the tube. It stopped that leak.