Inner Tubes

An inner tube is basically a doughnut-shaped balloon, with a valve for inflation. The only requirement for an inner tube is that it not leak. Being of rubber, it has no rigid structure. If an inner tube is inflated outside of a tyre, it will expand to 2 or 3 times its nominal size, if it doesn't explode first. Without being surrounded by a tyre, an inner tube can't withstand any significant air pressure.

Help With Tyre and Wheel Sizing