An inner tube is the tube inside a protective outer tire that is generally used to hold air and keep the entire tire inflated to a proper level. They are very fragile in many cases and therefore need some sort of outer protection in order not to become easily punctured. If one does become damaged, it may be possible to repair the inner tube with an inexpensive patch.
Not all tires have an inner tube, because they are able to hold air with other components. Most passenger car tires fall into this category. However, there are vehicles on the road, such as motorcycles and heavy trucks and tractors that may have inner tubes, though there may be other options for these types of vehicles as well.
When most people think of an inner tube, its application on a bicycle may be the first thing that comes to mind. For many, a bike may have been their first experience with an inner tube. If punctured, often a patch was all it would take to repair it. Of course, new ones could also be bought relatively cheaply.
Larger inner tubes have also been used for recreational purposes, such as tubing down rivers and in other bodies of water. In this application, an individual takes an inner tube and floats in it down a river. Inner tubing is especially popular in areas where the water is relatively clear, such as near a spring, or in mountain streams, where there could be low-level white water to help make things a little interesting. Another form of water tubing involves the inner tube being pulled behind a boat, much like a skier would be.
Such inner tubes can also be used on the slopes after a snow has fallen. They operate under similar principles of a sled, where gravity takes them down the hill at high rates of speed. While some sleds can be operated under the steering control of the rider, the inner tube offers no such luxury.
Whether is it on the slopes or in the water some tubes are specifically designed for such activities. As such, they may be wider and more stable than other types of inner tubes. Further, they may have flashy colors and even false bottoms for some protection from the elements. In such cases, these are not true inner tubes because they were never intended to be placed in any tire. Nevertheless, the term inner tube is acceptable for these products.