Bicycle tube
A bicycle inner tube is a container filled with compressed air, which seals the pneumatic tire (the blanket) from the inside against loss of pressure if the rim is not suitable for tubeless tires. It is part of bicycle tires and is made of butyl , previously also made of rubber .
history
Although this has recently been disputed, John Boyd Dunlop is considered to be the inventor of the pneumatic tire and thus also of the bicycle tube. He applied for a patent for the air-filled rubber tire on December 7, 1888; Édouard Michelin developed the interchangeable rubber tire with an air tube for bicycles in 1889 (Dunlop only invented an auxiliary tire for his son's tricycle). The vulcanization of rubber and hard rubber as the basis for later bicycle tires were invented by Charles Goodyear as early as 1839 . In 1845 the Scot Robert William Thomson patented air-filled animal casings as tires.
Tubeless tires have also been around for a number of years . These tires and rims form a tight air chamber and a conventional tube is no longer required. Tubeless tires have so far not been widespread on bicycles.
Bicycle tubes are available along popular (long-distance) cycle paths and at specialist shops from special machines.
construction
Butyl hoses are a little heavier than rubber hoses, are less sensitive to heat, very stable to air pressure and inexpensive to manufacture. Rubber hoses are lightweight and have lower rolling resistance, but are sensitive to heat and lose air quickly. They are more expensive to manufacture than butyl tubing. Recently there have been particularly light butyl hoses that are less than the weight of rubber hoses. Due to the thinner wall thickness of these light hoses, they are less stable to air pressure than ordinary butyl hoses.
In order to prevent the inner tube walls and tubes from sticking to the bicycle jacket or the rim tape , they are usually provided with talcum powder on the inside and outside . Hoses are brought to a specified air pressure with air pumps or compressors .
In addition to hubs, spokes and rims, tubular tires also require a bicycle jacket and a rim tape. The rim tape covers nipples or nipple holes and protects the tube from damage.
So-called tubular tires are often used on racing bikes , in which the tube and jacket are connected as a unit by placing the jacket around the tube and sewing it.
Air pressure
The more voluminous the jacket, the lower the air pressure can be without fear of a breakdown . The maximum allowable air pressure is indicated on the jacket.
If the air pressure is too low, the driver has to use energy to deform the jacket.
quality
Intact tubes also lose air through permeation , so that the pressure gradually decreases and the tire sometimes has to be inflated. This happens faster at a high temperature. As a result of aging, glued hoses and hoses with screwed valve seats lose more air than seamlessly vulcanized hoses.
In order to save weight despite the use of bulky (mountain bike) tires, lightweight tubes are increasingly being used, but these have a shorter life expectancy.
Sizes and designs
Since around 1995, so-called group hoses have been used, which cover a wider range of applications than the previously offered hoses, which should only be used with a special jacket width. If a wide jacket is used on a narrow rim (see: Bicycle tires # ratio of tire to rim width ), a wider tube should be used to compensate. Otherwise, the tube initially spreads out into the larger volume of the jacket when it is inflated and only then expands down into the rather narrow area of the rim. The inner area of the hose is overstretched, which can later lead to fine cracks on the inside of the hose, especially in the places that come to lie above the heads of the spoke nipples.
It is important that the tube fits the diameter of the rim . Hoses that are too short (wrong wheel diameter) are difficult to fit. Hoses with a diameter that is too small (e.g. a hose for 25 mm tire width in 47 mm wide tires) can be fitted, but are overstretched. Conversely, tubes that are too large can be inserted into the tire, but then lie in folds during operation, which often leads to an irregular deformation of the casing.
It is also important to ensure that the version with the appropriate bicycle valve is obtained. Reaming the rim hole to use a larger valve will compromise the stability of the rim.
handling
A puncture in the tube can be quickly repaired by the cyclist . For this purpose, special bicycle tube repair sets ( patch kits ) with solvent -based adhesives are offered, which, in conjunction with tools for dismantling the wheel and jacket, allow repairs on the go. For some years now, self-adhesive patches have also been on the market that do not require any adhesive to be applied and, in some cases, can even be glued on without roughening the rubber surface beforehand.
When repairing holes in thin-walled (lightweight) hoses, only sandpaper should be used for roughening. Sharp-edged, perforated sheets for roughening the joint, which are included with some repair kits, often remove too much material or scratch furrows in the material, which can lead to further leaks.
In the event of a gradual loss of pressure, the tight fit of the valve insert should first be checked. The tightness of the valve can be checked by holding a finger wetted with liquid in front of the opening of the valve. If bubbles form, a small amount of oil can be added to the valve to seal it. Under no circumstances should more than a small drop of oil be used, as many oils damage the rubber in the long term. If it is not on the valve, the inflated hose can be immersed in a water basin to find out where the leak is.
If the pressure loss occurs sometimes more quickly and sometimes more slowly, a fine gap may have formed between the valve connector and the hose, which allows the air to escape at different speeds depending on the load and the installation position of the valve stem. Such a gap cannot be repaired with a patch.
literature
- Fritz Winkler, Siegfried Rauch: Bicycle technology repair, construction, production. 10th edition, BVA Bielefelder Verlagsanstalt GmbH & Co. KG, Bielefeld, 1999, ISBN 3-87073-131-1 .
Web links
- (right): tire sizes and air pressure table (last accessed on May 13, 2015)