The tire's bulge (post #5 ) around the valve might be from poor tire mounting. If the tube/valve in not fully inside the tire beads, or if it is trapped under the tire's bead, then the tire will not fully sit down in the rim. The tube has a thicker portion around the valve that can easily be caught under the bead. When mounting the tire if the valve stem is pushed up and into the rim a bit the thick tube at the valve's base will fit up inside the tire and not be under the bead. The air pressure of the tire will push the valve back out as much as is needed. Andy.