Positive Displacemrnt

• A bike pump works basically through a compression system known as positive displacement. A piston inside the body of the pump pushes down and exerts air out the nozzle. When the pump is pulled up, air re-enters the chamber.
  
  

Attaching the Pump

• Most pumps have a nozzle that can attach straight to a tire. A small clasp on the nozzle can be locked into place that allows it to clamp to the bike. Most nozzles attach with some minor twisting.
  
  

Pumping

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  Because of positive displacement, a person has two options when pumping. They can go for quick pumps, which produces less air because the cylinder isn't refilling, but requires less force, or they can do a longer pump, which requires more pressure, but produces more air (and therefore fewer pumps).