[nkaminar]

The tire can be out of round if part of the flap is stuck under a section of bead.

I have had good luck with the stick-on lead weights. Back off the brake adjustment and back off the bearing nut a little bit until the wheel rotates freely. Rotate the wheel twice and if it stops in the same place, add weight at the top. Add the weights at the inside rim and clean the wheel before adding the weights. If you keep track of how much you backed off the brake adjustment and bearing nut, you can easily return them to their original position. Keep adding weight until the tire stops at random places.

The balancing beads work if the tire runs true, not out of round. It works at higher speeds and not at slow speeds. It works because at higher rpm than the critical speed the light side of the tire rotates at a bigger radius than the heavy side. So the beads migrate to the light side to balance the tire.