An inner tube is an inflatable ring that forms the interior of some pneumatic tires. The tube is inflated with a

valve stem A valve stem is a self-contained valve which opens to admit gas to a chamber (such as air to inflate a tire), and is then automatically closed and kept sealed by the pressure in the chamber, or a spring, or both, to prevent the gas from escaping ...

, and fits inside of the casing of the tire. The inflated inner tube provides structural support and suspension, while the outer tire provides grip and protects the more fragile tube. They are widely used in bicycles and are also used in many

motorcycles A motorcycle (motorbike, bike, or trike (if three-wheeled)) is a two or three-wheeled motor vehicle steered by a handlebar. Motorcycle design varies greatly to suit a range of different purposes: long-distance travel, commuting, cruising ...

and heavy road vehicles such as trucks and buses. They are now less common in other wheeled vehicles because of the benefits of having no tube, such as the ability to operate at

low pressure In meteorology, a low-pressure area, low area or low is a region where the atmospheric pressure is lower than that of surrounding locations. Low-pressure areas are commonly associated with inclement weather (such as cloudy, windy, with possible ...

and at

high pressure In science and engineering the study of high pressure examines its effects on materials and the design and construction of devices, such as a diamond anvil cell, which can create high pressure. By ''high pressure'' is usually meant pressures of th ...

(unlike a tube tire, which would pinch at low

pressure Pressure (symbol: ''p'' or ''P'') is the force applied perpendicular to the surface of an object per unit area over which that force is distributed. Gauge pressure (also spelled ''gage'' pressure)The preferred spelling varies by country and e ...

and burst at high

), without going flat. Large inner rings also make effective

flotation device A personal flotation device (PFD; also referred to as a life jacket, life preserver, life belt, Mae West, life vest, life saver, cork jacket, buoyancy aid or flotation suit) is a flotation device in the form of a vest or suite that is worn by a ...

s and are widely used in the leisure activity of tubing.

Material

The tube is made out of a mix of natural and synthetic

rubber Rubber, also called India rubber, latex, Amazonian rubber, ''caucho'', or ''caoutchouc'', as initially produced, consists of polymers of the organic compound isoprene, with minor impurities of other organic compounds. Thailand, Malaysia, an ...

. Natural rubber is less prone to punctures and is often more pliable, while synthetic rubber is cheaper. Often racing bikes will have a higher percentage of natural rubber than regular bikes.

Performance

Inner tubes will wear out over time. This makes them thinner, and more likely to burst. According to Dunlop, inner tubes should be changed Gearbikesreview
How to Change a Inner Tube
every 6 months. Inner tubes also tend to be slower than

tubeless tires Tubeless tires ( also spelled as tubeless tyres in Commonwealth English) are pneumatic tires that do not require a separate inner tube. Unlike pneumatic tires which use a separate inner tube, tubeless tires have continuous ribs molded integral ...

because of the friction between the casing and the inner tube. Tires that use tubes are on average lighter, as the tube can be made relatively thin. As the tubing is sown to the tire, if punctured, the tire can still be ridden flat. They are reportedly more comfortable to use, if attached to the bicycle properly.

References

{{reflist Tires

Material

Performance

See also

References