prestas

Prestas, or Presta valves, are a type of bicycle tire valve used on inner tubes and many tubeless rims. They are slender and designed for high-pressure tires, and are commonly referred to in Europe as the Sclaverand valve. The Presta valve is also known as the French valve, and in some contexts distinctions are made from the Schrader valve.

Design and features: A Presta valve consists of a narrow, threaded metal stem with a removable valve core inside. It is closed by a small end cap and opened for inflation by unscrewing the end to allow air flow. The valve threads into the rim and is sealed with a rim-grommet or washer in tubeless installations. Some versions use a removable core that can be serviced with a valve-core tool. The outer diameter is smaller than a Schrader valve, which allows use in rims with smaller holes and tighter clearances.

Usage and compatibility: Presta valves are standard on many road bikes and a subset of mountain bikes. They require a pump head designed for Presta valves or an adapter to fit a Schrader pump. For rims with deep-profile or wide interiors, longer Presta valves or valve extenders may be used. Tubeless systems often rely on Presta valves with appropriate seals and sealant.

Maintenance and notes: Keep the valve cap on to protect the valve from dirt. Periodically check for leaks around the rim hole or at the valve stem, and replace a faulty valve core if needed. When transporting wheels, ensure the valve is not bent or damaged.

See also: Schrader valve, valve extenders, tubeless tire systems.