He’s since been indoctrinated into gravel riding and more recently has taken to the dark art of mountain biking. He has been an avid cyclist since his teenage years, initially catching the road cycling bug and riding for a local club. Oscar Huckle is a technical writer at BikeRadar. Presta valves will close automatically, but the sprung Schrader valves are usually held open by a pin in the pump valve attachment (this means you don’t need any extra effort when pumping to overcome the pressure exerted by the spring). If it wasn’t there, the pump would just shoot open again. To prevent the pressure in the tyre leaking back out, the second check valve at the base of the pump closes. You extend the pump again, the check valve opens to refill the chamber with air and you repeat the process. That pressure increases until it exceeds that inside the tyre.Īt this point, a second one-way valve will allow air to flow from the pressurised pump chamber into the tyre. On a pump’s downstroke, a check valve (that allows air flow in one direction) seals the piston chamber, resulting in air being pressurised as the pump is compressed. This ‘overpressure’ forces air into the tyre, increasing its pressure too.Ī pump is just a manually actuated piston. The operating principle is simple you increase the pressure inside the pump until it exceeds that inside the tyre. Nick Clark / Our MediaĪ pump gets the air into your tyre.
Some pumps feature rubberised handles for improved grip.
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