Inner tubes explained
An inner tube is a balloon-like structure that can be inflated and deflated via a valve. Inner tubes are on all bike wheels other than tubeless/tubular options. Upon first inspection it's easy to think that an inner tube will not stretch enough to fill the tyre with air, but they certainly do. When the inner tube is inflated, it fills the gap between the inside of the sidewalls of the rim and the inside of the bike tyre.
Wiggle recommends: The LifeLine Road Inner Tube is one of our best selling and most popular inner tubes.
What inner tube do I need for my bike?
Inner tubes come in a variety of styles. There are two main things to consider; size and valve type.
Size
Inner tubes are very versatile and cover a variety of widths, but generally only cover one diameter of wheel with the exceptions including some children's bikes. Have a look at your tyre, you will see some numbers either printed or embossed onto the sidewall. These numbers represent the tyre dimensions that determine the inner tube size required. For example, on a road bike tyre you may see the writing 700x23.
Wiggle recommends: The LifeLine Wide Road Inner Tube is perfect if you run 700cc rims with wide tyres.
- See more at: http://guides.wiggle.co.uk/inner-tube-buying-guide#sthash.p0wk0fkE.dpuf