Anyone who has cursed a flat tyre at one time or another knows it: nothing works without air in the tyre; well, except pushing. The inner tube is responsible for holding air inside the tyre, but most cyclists rarely take notice of it – except when there is a hole and a loss of air. Apart from that, the only part of the inner tube that is usually visible is the valve, which protrudes through the rim. The inner tube itself is hidden under the coat and rim, where it performs tireless hard labour and withstands enormous strains and temperature differences during sporting performance. It is also particularly important that it is responsible for adjusting comfort and riding experience. The correct air pressure in the tyre provides damping and grip and influences rolling resistance and roadholding on curves. An inner tube has to perform a good deal, which is why it is just as important to take a look at this part of the bike.
Inner tubes in different sizes
Classic inner tubes are made of butyl rubber. This is a synthetic rubber that has very low air permeability, is very weather resistant and maintains its high stability and elasticity at any temperature.In short: the rubber tube absorbs the air and, generally speaking, does not release it again – regardless of conditions such as winter mountain biking on snow and ice or scorching heat on hot asphalt. In addition to butyl inner tubes, there are also inner tubes made of latex. They are very light, but not as airtight as the rubber ones. For this reason latex tubes have to be inflated more often.
Depending on the type of bike, rim diameter, rim width and tyre coat, cyclists use different sizes and widths of inner tubes. Particularly light and thin-walled tubes are required for certain areas of application. Other cyclists place a lot of emphasis on stability and choose thicker-walled and heavier tubes accordingly. Furthermore, there are different types of valves used on inner tubes:
- The Dunlop valve (DV) or normal valve (NV) is very widely used for everyday bikes, Dutch bikes, touring bikes and children’s bikes in Germany. It is designed for a maximum pressure of 6 bar and fits into a rim hole with a 8.5 mm diameter.
- The Sclaverand valve (SV), also referred to as “French valve” and “road bike valve”, has a smaller diameter (rim hole 6.5 mm) and allows a maximum air pressure of 15 bar. Due to its high possible air pressure and the associated low rolling resistance, the Sclaverand valve has long been popular with road cyclists. However, this particular valve is now also widely used on mountain bikes.
- The Schrader valve is better known to most cyclists as an auto valve (AV). This valve used to be the standard choice for mountain bikes. On the positive side, cyclists with these valves hardly need to worry about an air pump, because their bike can be inflated at any petrol station.
Since the rim hole differs depending on the valve, cyclists must select the inner tube with the appropriate valve. Otherwise the valve would not fit through the rim at all or there would be too much clearance and it would not sit properly in the hole.
When buying inner tubes, three criteria are decisive in addition to weight and material thickness:
- Wheel size / diameter of the wheels: these values are given in inches. Common values for mountain bikes are 29 inches (29″), 27.5 inches (27.5″) or 28 inches (28″) for road bikes.
- Rim width / tyre width: depending on the rim width (i.e. the inner width of the rim) and the desired tyre width, the tube must be selected to match.
- Valve type: this must match the rim hole.
Depending on the area of application, the tubes are designed for an individual maximum pressure. This is where road bike tyres (which are ridden with very high pressure) differ from cyclocross tyres, downhill tyres, trekking tyres or road tyres for everyday bikes. Since the tubes also differ greatly in dimensions (rule of thumb: road bike narrow, trekking bike medium, mountain bike wide), fortunately there is little danger of confusion here. The dimensions of the inner tubes are also indicated on the packaging as well as on the inner tubes themselves. Some tubes are even made to ideally fit several rim diameters. Here, too, the corresponding measurements are recorded on the packaging. High-grade inner tubes from renowned manufacturers, such as Schwalbe, Continental or Michelin, convince with their high quality standards and the associated reliability. With these manufacturers, every single tube is tested for absolute air tightness before it is delivered.
For a few years there have also been some well-functioning tubeless systems around for mountain bike tyres especially. Tubeless means that the manufacturers completely dispense with inner tubes. Instead of the inner tube, air is simply trapped between the tyre coat and the rim.Although the tubeless system requires more assembly work and is associated with higher costs, tubeless tyres are less prone to breakdowns and offer a very good riding experience. While tubeless tyres have been used widely among mountain bikers in France for quite some time, cyclists in German-speaking countries still tend to use the good old inner tube. Some reasons for this could be the simple assembly and the high reliability.
Depending on the bike and the area of use, different rims, different tyres and, of course, different inner tubes are used. This is why we have compiled a compact overview of the different tubes here:
Inner tubes for road bikes
For road bikes, 28″ tubes are mostly used. In triathlon, road cyclists also like to use the smaller 26″ tubes. Since some inch specifications can differ for both the rims and the tyres, road cyclists should measure their tyre size exactly beforehand.
The decisive value is the distance from rim well to rim well. Measuring and converting into inches saves many a surprise when buying inner tubes and tyres. The equally important rim width is usually printed on the rim. Since France has its own measurements in addition to the general deviations with the inch measurements, it is advisable to select the tubes and tyres according to the ETRTO (European Tyre and Rim Technical Organisation) specifications. These are given in exact millimetres which makes comparison and selection much more convenient. If you are using high-profile rims, you should also pay attention to the length of the valve when buying a tube. At Schwalbe, for example, these tubes are marked “Extra Long” or “XX Long”.
Inner tubes for mountain bikes
Many mountain bikers ride with 26″ wheels, but 27.5″ and 29″ are also widely used dimensions. Using an appropriate jaw width and tyre width, most inner tubes for mountain bike tyres range in width between 2.25″ and 2.35″. The tubes usually offer a certain tolerance and can be ridden with different tyre and rim combinations. However, when installing a smaller tube in a very large rim, the load increases and with it the risk of breakdowns.
Mountain bike tyres offer a good balance of stability and weight at around 150 g to 200 g. Lighter tubes are available, but are more commonly used for touring and cross-country, as their lightweight construction also makes them more prone to breakdowns. Downhill bikes and Enduro bikes, on the other hand, use particularly thick downhill tubes. These are extremely stable, but with their high weight they are only suitable for normal MTB tours to a limited extent.
Inner tubes for trekking bikes and touring bikes
High reliability and a pleasant riding experience are crucial for cycling tours and cycling journeys. Tyres and tubes are mostly 28″ and weigh only about half as much as MTB tubes. In addition to good durability and stability, high-quality trekking tubes ensure low rolling resistance.
Inner tubes for children’s bikes
Depending on whether the children’s bike is an everyday bike, a mountain bike or BMX, the tubes for children’s bikes are sometimes made more robust and sometimes a little lighter. Inner tubes for children’s bikes start at 10″ or 12″ and are usually suitable for several wheel sizes. The tubes for youths’ bikes are available up to a size of 24″ – after that, with 26″, begins an area where youth and adult sizes are starting to overlap.
Inner tubes for e-bikes and fatbikes
With e-bikes, strains on tubes and tyres are greater than with conventional bikes due to higher average speeds. Tubes must therefore be particularly resistant and durable. Above all, this applies to e-bikes, which have a license for motor assistance up to 50 km/h. On a fatbike, not only are the rims and tyres oversized, but so are the inner tubes. For a rim size of 26″, there are tubes between about 3.5″ and 4.8″. Of course, fatbike tubes are heavier than ordinary MTB tubes – but they fit the entire fatbike set-up without compromise.
Changing and patching an inner tube
Repairing inner tubes is simple and can be done with little effort by any cyclist. Due to this simple handling, the pro-tube version is still the most widely used. All that cyclists need to change the inner tube is a repair kit with appropriate materials for patching and a few tyre levers to gently remove the tyre from the rim. Many tyre patches are self-adhesive and are stuck onto the damaged area like a sticker. Afterwards, the inner tube is ready for use again in no time and can be installed and inflated. Small holes in the tube can be repaired in this way. Only in the case of longer cuts and damage to the valve a new inner tube is often needed.
This small overview shows that there are a lot of things to consider when it comes to valves and tubes. It is important that both components fit, not only in terms of their size, but also in terms of the bike’s area of use. Do you have any experience with inner tubes, or do you have any unanswered questions? – Feel free to leave your comments!