Originally Posted by
dsbrantjr
If your rim has a thick cloth tape such as Velox, you could try a thinner tape such as Continental Easy Tape or a layer of filament-reinforced packing tape or Kapton tape. The thinner tape should make tire mounting easier by allowing you to get the bead deeper into the center of the rim channel.
Yes, the shape of the rim above, it appears to be a standard rim, without the new tubeless shelf that causes so many people problems.
I'd also look at the tape.
Another option are
veloplugs. On occasion, I've gone over the veloplugs with a thin layer of tape like electrical tape (or stronger tape).
The veloplugs provide the strength, and the tape keeps them from moving, and keeps the tube inside.