Your bike’s inner tube is an inflatable tube made of synthetic rubber which sits inside the tyre and makes it airtight. Most bike wheels – road, city bike, MTB etc. – still use inner tubes to hold the air, although in recent years car-style ‘tubeless’ tyres have grown in popularity.
Your inner tubes are one of those things on the bike that you are never aware of until things go wrong – i.e. you have a puncture that has gone through the tyre and pierced the tube. If this happens, your inner tube can be patched using a puncture repair kit, but if the hole is too big (or you can’t be bothered, let’s face it), you’ll have to get a new tube.
There are two things to bear in mind when replacing a tube:
1. Wheel size: This will differ between bike types – generally there are a limited number of standard sizes between road and MTB bikes but there can also be deviations in width and volume etc.
2. Valve type: The tube is inflated via a valve which fits through a hole in the rim of the wheel – there are a few different types of valves so when replacing a tube it’s important to ensure you have the right one, or it may not fit through the rim hole.
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Which size for my bike?
Firstly, determine the size you need – this will be decided by the size of your wheels and tyres.
In most cases, you can look at the sidewalls of your tyres and see a series of numbers printed there which represent the size of your tyre – this is the size tube you need too. Most tyres will display both an ETRTO (European Tire and Rim Technical Organisation) or ISO (International Organisation for Standardisation) size as well as the ‘traditional’ size in Metric (mm) or Imperial (inches).
(The ETRTO and ISO are organisations which aim to standardise tyre and rim sizes globally and remove some of the confusion caused by the use of different standards – most manufacturers still use the ‘traditional’ sizing as well)
So the ‘traditional’ sizing will show the diameter of the wheel and the width of the rim in the form ‘Diameter X Width’. In this case the typical road bike wheel of 700c in diameter might have a sizing of 700×23 (700c is the diameter, 23mm is the width). A mountain bike wheel (with dimensions measured in inches), may show the size 26×2.1 (26 inches being the diameter, 2.1 inches being the width).
In each case you will need a tube to fit – in the case of the road bike a 700 x 18-23/25c tube will be ideal (with 18-23/35c being the range of tyre widths it can fit) and for our MTB we will need a 26 x 1.75-2.5” tube.
Still with us? Good.
In reality it’s not that complicated – most road bikes take a standard-sized tube to suit a range of the most common rim widths (700c), and will likely say ‘road bike tube’ in the description anyway. Same for BMX tubes (20”). However with MTB and hybrid/city bike tubes it’s worth remembering that a number of different rim diameters are in common use, so be mindful of whether your bike has 26”, 27.5” or 29” rims.
Which valve type do I need?
Once you have the size of your wheels you’ll need to know which valve type your tubes have.
There are two main types, Presta and Schrader.
Schrader valves are also sometimes known as ‘car-type’ valves as they are the same type used on motor vehicle tyres. Schrader valves are often found on MTB tubes, commuter bikes, kids’ bikes and BMXs. To inflate or deflate a Schrader valve you simply remove the valve cap, press the pump nozzle against the valve until the central pin depresses, opening the valve, and off you go.
Presta valves are usually found on road bikes and some higher-end mountain bikes. They are available in different lengths so can be used to fit tubes on aerodynamic, deep-section racing wheels. Presta valves typically feature a threaded exterior onto which is wound a circular locknut, which keeps the valve tight to the wheel rim and prevents it twisting off or becoming damaged during inflation. Inflating a Presta valve also involves unscrewing a small nut at the very tip to open the valve before then attaching the pump nozzle – to deflate the tube you unscrew this nut and press it in to let the air escape.
Presta valves will sometimes feature a removable valve core, which allows riders with deep-section rims to use valve extenders, or which enables latex sealant to be put into the tube as added puncture protection.
Anything else I need to know?
While most inner tubes are pretty standard – balloons to hold air – you can get heavy-duty versions that are more suited to the rigours of disciplines such as downhill racing (DH), but with a weight penalty.
Finally some tubes are available with liquid latex sealant already inside, the idea being that in the event of a puncture, the sealant hardens around the hole without the need for the tube to be repaired or replaced. These are more expensive and a little heavier than standard tubes, but have their fans among city commuters and road riders/tourers who swear by them.
Valve extenders are used to add length to standard Presta valves so that they can be used with aerodynamic deep-section rims.
They are available in a number of different lengths to suit rims of varying depths. Your tube’s valves must have a removable core in order to allow the use of valve extenders.