French valve

What is a "French valve"?

The "French valve", also known as "Sclaverand valve" or "Presta valve", is a type of valve commonly used in bicycle tires. It is named after its inventor, the French cyclist and valve manufacturer René Sclaverand . The French valve is characterized by its sleek shape and its specific mode of operation.

Structure and function of the French valve

The French valve consists of a thin metal tube with a thread at the top end that is inserted into the valve hole of the rim. The valve is secured to the bottom end of the rim by tightening a nut, creating an airtight connection. There is a cap at the top of the valve that serves to protect against dirt and moisture and is removed during inflation.

To let air into the tire, the cap must be unscrewed. A special valve core is pushed in slightly to allow air to pass through. When the tire is inflated, the air from outside pushes the valve core down, and when the desired pressure is reached, the valve core is closed by the elastic force of an integrated rubber membrane.

Advantages of the French valve

1. Thin construction: The slim profile of the French valve allows for smaller valve holes in the rims, resulting in less material removal and thus increasing the stability of the rim.

2. Higher pressure: The French valve can handle higher tire pressures, making it a popular choice for road bikes .

3. Tight closure: The valve closes automatically and tightly, minimizing air escape and allowing easy inflation.

4. Narrow Rim Compatibility: The slim design of the French valve makes it ideal for narrower rim profiles.

Disadvantages of the French valve

1. Special pump head required: Many standard bike pumps come with a larger pump head for Schrader valves. An adapter or special pump head is required to inflate the French valve.

2. More sensitive: The French valve can be more sensitive and more prone to damage than Schrader valves.

3. Bleeding when screwing on the cap: If the valve cap is not tightened properly, there may be a slight escape of air.

Comparison with other valves

• Schrader valve: The Schrader valve is more robust and is often used in car valves . It does not require special pump heads, but its larger design can affect the rim profile.

• Blitz valve (Dunlop valve): The Blitz valve is a compromise between Schrader and French valve and requires a special pump head. It is common on city bikes and Dutch bikes .