Perfect for mountain bikes, e-bikes, trekking bikes, enduro, downhill & freeride: Schwalbe's 21F tube fits all tires from 1.90 to 3 inches and is available with Sclaverand or car valve.
Schwalbe bicycle inner tubes are typically made of butyl rubber. Butyl is a highly elastic yet airtight synthetic rubber. Before extrusion, the base material is forced through seven filters under enormous pressure. All tubes are then placed in a mold and inflated for vulcanization. This is the only way to guarantee consistent wall thickness and excellent air retention. All finished tubes are inflated and stored for at least 24 hours to test their air retention. Afterward, each tube undergoes a thorough visual inspection. For many years, German bicycle retailers have valued Schwalbe inner tubes for their exceptional reliability. Every Schwalbe inner tube is 100% recyclable. Schwalbe can use recycled butyl rubber in the production of new tubes without any loss of quality. Therefore, every new standard Schwalbe inner tube already consists of approximately 20% recycled material. This process consumes only one-fifth of the energy required to produce the same amount of virgin butyl.
In this chapter, we explain the technologies that the manufacturer uses in this product.
car valve The car valve can be filled very easily at the petrol station.
Sclaverand valve The Sclaverand valve is narrower than other valves (6 mm instead of 8 mm). It requires a smaller rim hole and is therefore particularly well-suited for narrow road bike rims. It has also become established on many mountain bikes.
Dunlop valve The classic bicycle valve, or Dunlop valve, is still the most common type on city bikes. Most bikes are familiar with it. The valve core is easy to replace, and air can be released very quickly. However, fitting a tube with a Dunlop valve is more involved because the valve has to be disassembled and reassembled.
