The Presta valve is commonly used on high-pressure road and racing bicycle tires, although it can be found on mountain machines, as well. Presta valves are tall and thin, with an exposed valve stem that is locked by a small nut. Inflating tires with these valves can be frustrating, but many cyclists find they prefer the Presta valve after getting familiar with it.
Rotate the wheel so the valve is resting just above the floor. Remove the valve cap.
Unscrew the locking nut on the valve stem. Quickly press down the stem to loosen the seal. You should hear air escaping when the stem is pushed in--if you do not, loosen the nut and try again.
Press the pump head onto the valve and flip the locking lever to make a seal. You'll hear air escape, but it should stop after you've locked the lever. If air continues to leak out, remove the pump head and reattach it.
Make two pump strokes and listen for air moving into the tire. If the pump handle becomes hard to press down after only a few strokes, or if the pressure gauge elevates extremely quickly, remove the pump head and repeat Step 3.
Inflate the tire to its recommended pressure. Remove the head by unlocking its lever and quickly pulling it off the valve stem. Secure the valve's locking nut and cap.