Metal Presta valves on bicycle tires are sometimes known as French or skinny valves. As opposed to Schrader valves, which resemble car tire valves and are more common on U.S. bicycles, Presta valves require a pump with a different connector than Schrader valves use. Several pump designs can handle Presta valves, including pumps dedicated solely to Presta valves, those with separate connectors for each type, a unit with a reversible gasket that handles both valve types, or one equipped with an adapter that converts from Presta to Schrader. At least one pump manufacturer, Topeak, has patented a pump head that detects the valve type automatically.
Place your bike on a mount, upside down or however you normally do to pump up the tires. Rotate the wheel so you can easily reach the Presta valve. If the Presta valve has a cap, which isn't truly necessary for valve function, unscrew the cap counterclockwise and set it aside in a safe place.
Unscrew the knurled tip of the Presta valve all the way, counterclockwise, to open the valve. The tip will rise but not come completely off the valve, but it must be raised for the valve to accept air. Push on the valve for a moment so you can hear some air escape to ensure the air pathway is open.
Place a Presta nut over the valve and turn it clockwise until it is seated next to the bicycle tire rim, thus holding the Presta valve above the rim. This step is optional, but very convenient because the pump connector will probably need to be pushed onto the valve. With a deflated tube, the valve may slide inside the rim, making it difficult to attach the pump correctly. Hand tighten the Presta nut only, and do not overtighten, or you could pull the valve up far enough to puncture the tube. Presta nuts can be used only on Presta valves threaded all the way down to the tube.
Fit your pump head with the Presta connector if it has two connectors. For pumps with reversible rubber gaskets, move the gasket so that the Presta opening, usually the smaller hole, is in position to be used. If your pump needs an adapter to convert to Presta valve use, attach the adapter. If your pump is designed only for Presta valves, or if it is the type whose end works on both valve types, you do not need to make any changes.
Slide the pump end connector over the open Presta valve and secure it according to the pump's design. Many pumps require you to flip a lever opposite the valve hole to secure it to the valve. In any case, ensure the connection is airtight.
Inflate the tire with the pump to the recommended psi (pounds per square inch) stated on the sidewall of the tire. If your pump is a frame-mounted manual model, hold the end of the pump connected to the valve in one hand while pumping with the other. Hook a finger around the tire on the hand holding the pump end so the pumping pressure presses against your hand, not the valve itself. This helps spare the valve from possible damage.
Remove the pump connector from the Presta valve, flipping the lever or taking whatever steps are necessary to disengage the pump from the valve first. If the pump sticks on the valve, gently move it back and forth to work it loose, but do not forcibly pull the pump connector off the valve. Pulling on the valve can damage the tube inside.
Screw the knurled tip of the Presta valve back down onto the valve stem in a clockwise direction. Remove the Presta nut, if you used one. Screw the cap back on the valve, if you use caps.
- To use a Schrader pump on a Presta valve, buy a Presta-to-Schrader adapter. The adapter threads onto the open Presta valve and presents a Schrader-ended valve for pumping. This can be handy if you have a flat while riding and must use a gas station pump. Remember to take off the adapter to close the Presta valve tip after inflating the tube. Some riders then put the adapter on the closed Presta valve and ride with the adapters on the tires.
- If your Presta valve has two flat areas just below the valve tip, it has a replaceable core. Tighten this type periodically with an adjustable wrench on the flats to eliminate the possibility of slow leaks at the valve. If you use a CO2 inflator on this type of Presta in damp weather, the cold CO2 can freeze the inflator to the valve. To prevent the core from coming out of the Presta valve when you unscrew the inflator, put a little water on the valve tip before you remove the inflator.
- Check for a slow leak in the valve by putting a little spit on the valve end to see if a bubble forms. If it does, you have a slow leak and must tighten or replace the valve or its core.
- The rim hole for Schrader valves is bigger than the hole for Presta valves. If you have a Presta valve in a Schrader hole, use a rubber ring grommet in the hole available at bike shops to keep the Presta valve from sliding around and damaging the tube or the valve itself.