Originally Posted by
BlazingPedals
Tubes don't spontaneously explode. The tire prevents it. Unless you've mounted them poorly and left a bit of the tube pinched under the tire bead.
Regarding the bulge, the tube is fatter there because the air tends to stay on that side of the tube, where it first goes in. <g>
Yes, and no in that order.
Yes, the tube doesn't offer structure and will not explode unless the there's a gap (usually from poor mounting) which allows it to balloon out.
No, the air doesn't magically stay closer to where it went in. Air has so little viscosity that for all practical purposes we can consider the pressure in any closed vessel to be equal throughout.
Tubes expand unevenly outside the tire because of the relative actions of increased tension as they stretch, and increased hoop stretch as the diameter increases. Anyone who's blown up a long balloon has seen this effect as the balloon first expands in one area, then continues to expand along its length, then when the full length has expanded then continue to expand somewhat evenly.
Minor variations in the material or thickness will cause some areas to expand first in any tube, but once there's serious pressure combined with the constraint offered by the tire the tube will simply stretch until it's pressing evenly up, down and sideways all the way around