There are many different types of inner tube available so it is important that you get the right tube for your bike, and to suit the riding that you are doing. For instance for occasional leisure use you probably don’t have to be too concerned, but might want to consider the durability and puncture protection that an inner tube offers. For competitive road racing or time trial you might want to consider the weight, to gain a performance advantage, and be prepared to take a bit more of a risk of puncturing. For downhill mountain biking puncture protection is likely to be your highest priority.
Choosing Your Inner Tube Size
It is imperative that you replace your inner tubes with a tube that is the right size according to the diameter and width for your tyre. The size is almost always written somewhere on the sidewall of the tyre for easy reference.
Inner tubes typically state a wheel diameter and width range for which they will work, e.g. 26 x 1.95-2.125", indicating that the tube is intended to fit a 26 inch tyre with a width of between 1.95 inches and 2.125 inches. Another example might be 700 x 18-23c, which seems less obvious but 700c is the diameter of road, cross and hybrid bike wheels, and the numbers relate to the width in millimeters, so 18mm-23mm wide.
Butyl or Latex?
Butyl rubber is the industry standard for common replacement inner tubes, offering a relatively cheap and readily available replacement product. However, more expensive tubes made from latex rubber also exist.
Latex rubber tubes offer slightly enhanced handling characteristics. As latex rubber is slightly more flexible than traditional butyl rubber, the tubes adapt quickly to the tyres changing shape while cornering and on impacts. Latex tubes generally have a thinner wall, offering obvious weight savings.
Despite their obvious advantages, it is important to recognise their flaws. Latex rubber reacts badly to contact with some oils and greases so must be handled carefully in the workshop. Also Latex is more gas permeable than butyl rubber and, as a result, latex rubber tubes do not hold the air as long as butyl based tubes and require more frequent inflation.
Inner Tube Valves
There are three types of valve used in bicycle inner tubes, but on the modern designs really only two commonly exist. They are Schraeder and Presta, as described below:
Schraeder valves are the same valves used on all automotive tyres and are often referred to as ‘car type’ valves. On bikes, Schrader valves tend to be used on lower pressure tyres, such as children’s bikes and mountain bikes. Schraeder valves have a core that is sprung loaded, and the central pin can be depressed with a narrow object to release air from the tube. The spring mechanism keeps the valve closed.
Presta valves are usually found on higher pressure tubes such as on a racing bike, hence they are often referred to as ‘Racing Valves’ although they are now used on all UST or "tubeless" mountain tyres too. The valve has a slimmer stem, sometimes threaded to accept a locking ring, which holds it tight in the rim drilling. To inflate or deflate via Presta Valve, the top section must be unscrewed, allowing the core of the valve to be free to move. This will allow the valve to open and close. In this ‘high pressure ‘ valve it is the air pressure that shuts the valve and then the closing of the top section that keeps it shut.
Woods (or Dunlop) valves were once popular on bicycles tyres in Great Britain and Asia. These are now rare, almost obselete, only to be found on much older bicycles. They look a little like a cross between the two ther valves, with a wider lower section, like the Schraeder, then a collar and a narrow top section, like the Presta. As the rim drilling is the same for both Woods and Schraeder, it is easy to replace the older tubes with the more modern variety.
When buying new inner tubes it is important to consider what type of valve you require, as the wheel rim is drilled for a certain type of valve. A rim drilled for presta means that a Schraeder tube will not fit through the hole, although the other way around is of course possible. Bear this in mind both for buying replacements and for carrying spares.
Presta inner tubes are available in different valve lengths to be appropriate for use in deep section rim profiles. If you have deep section rims, make sure the valve is long enough to extend through the rim hole, and still leave enough valve stem showing to fit the pump onto. Valve extenders can be purchased to make a shorter valve fit, and are also a good idea to carry as an emergency spare if you know your tubes require it, and you might get caught out. A fellow rider will be able to lend you a tube that would not usually fit, if you have an extender with you.