The inner tube of your dirt bike: This is what you need to know!
Inner tubes are a mix of natural and synthetic rubber. Natural rubber is more flexible and offers better puncture resistance, but synthetic rubber is cheaper. Expensive racing tires generally have a higher percentage of natural rubber to better shape the tire and prevent punctures. There are also solid foam rubber inner tubes (so-called bib mousse) that simulate the air pressure of a foam rubber inner tube.
For a motorcycle manufacturer, inner tubes are an easy product to save weight and money. Most motorcycles are equipped with thinner and cheaper inner tubes. Since the mass of an inner tube is unsprung weight, it's a great place to save weight. Conversely, almost every factory machine runs with heavy-duty tires (or foams) to prevent leaks.
Size matters! The correct size of inner tube is important for performance and prevention of pinching. If you install a 110 inner tube in a 100-pack tire, you will run the risk of pinching the excess rubber with a tire iron. An inner tube that is too small will need to be over-inflated to compensate for the size difference. Excessive tire pressure weakens the inner tube's ability to resist damage. It is possible to use a smaller inner tube to save weight, but it is not recommended.
Snake bite
Inner tubes play a big role in the feel and performance of the tire. Inner tubes should be the right shape and size to sit flush against the sidewall for a good, consistent feel. If there are areas where the inner tube does not maintain contact, the tire will feel soft and provide little confidence.
Inflating an inner tube to the correct pressure not only provides more sidewall strength, but also prevents leaks due to the so-called “snake bite”. Keep 0,8 bar as the standard pressure for your tires. Make variations from this value depending on the condition and nature of the substrate. Please note that if the tire heats up during use, the internal pressure can increase by as much as 0,3 bar. This can be reduced by blowing nitrogen into the inner tubes to avoid water content and heat expansion.
Bib mousse
Inner tubes are available in different thicknesses to provide the right level of puncture protection. A thin inner tube is approximately 1,5 mm to 1,75 mm thick. A heavy-duty tire is approximately 2 to 3 mm thick. And a super heavy duty tire is 3,5mm to 5mm thick. The weight of a thin inner tube is approximately 1200 grams, while a 3,5mm super-heavy-duty weighs 1700 grams. For comparison, a bib mousse weighs 1950 grams.
Talcum powder. If you have a baby at home, this potty is definitely on the counter. If an inner tube is not installed properly, it can become punctured. Using cornstarch or baby powder on the inner tube during installation will reduce friction between the inner tube and the tire carcass, making the tire last longer. Adding a little air to shape the tube before installing the tire can help prevent pinching during tire installation. Talcum powder is cheap and widely available.
The valve is the weak point of an inner tube. It is vulnerable to damage and leaks. The valve is vulcanized into the inner tube and can be torn off as the tire spins on the rim, so make sure the rim clamp is properly installed. Never tighten the valve nut down to the rim. Releasing the nut will allow the tire to rotate a little without tearing the valve off the tire. Make sure to re-center the valve when you see it at an angle. Turn the tire until the valve is straight again.
Replace in time
An inner tube is made to withstand the force of an outer tyre. However, if water or dirt gets between the tire and the inner tube, it will rub against the inner tube. Make sure that no contaminants can enter through the rim clamp or valve holes. Replacing the stock rubber rim tape with duct tape makes it more difficult for moisture to penetrate past the spoke nipples.
Even if your inner tube has never been punctured, it can wear out. Some manufacturers recommend replacing the inner tube every six months, but this mainly depends on the number of races you participate in. How do you know when an inner tube needs to be replaced? Check whether it does not stick to the tire, whether the rubber discolors (an old tire changes color from gray to black) or whether the printed text on the tire fades. If in doubt, replace the inner tube anyway. It is an inexpensive part that can save you a lot of headaches.
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