Bike Valves are a cycling essential that can be found in high pressure road bikes and some mountain bicycle’s inner tubes. The purpose of the valve is to control the amount of air in an inner tube. Today we are going to discuss all things bike valves from why they exist, what they do and the different types available.
Why Do Inner Tubes Have Bike Valves?
There are two main reasons why an inner tube has a valve which are:
- The first reason why an inner tube has a bike valve is to allow air to enter the inner tube. The valves are where the air gets into the inner tube. A valve includes a mechanism that allows air in and then can close to stop the air from escaping.
- The second reason is to allow the air to leave the inner tube. Sometimes we need to release the air from the inner tube. We might need to fit a new tyre, reseat the current tyre or allow the tyre past the brake blocks.
What Is The Purpose Of a Bike Valve?
A valve is used to control the amount of air in an inner tube. When the cylinder in a bicycle pump is compressed, air is pushed down the tube of the pump and then into the inner tube via the valve. After that, this is then forced open by the pressure of the air. When the handle of the pump is pulled up again, the valve shuts off automatically so that the air cannot escape from the tire, and new air is sucked into the cylinder so the process can be repeated.
On top of the valve there should be a dust cap. This is designed to keep debris out of the valve. Standard issues are plastic, generally black, but different coloured plastic or aluminium ones are available. BMX riders will sometimes pimp their ride with funky shaped dust caps, such as skulls or dice.
Different Types Of Bike Valves
Throughout the history of the bicycle, different bike valves have been developed and subsequently fallen out of use. Now there are two main types of valve, presta and schrader.
The Schrader valve consists of a 8mm diameter stem into which a valve core is threaded. The valve core is assisted by a spring, this is called a check valve that is meant to allow airflow in only one direction; the Schrader-valve tube requires pressure on the inner pin to let air in. If the valve core is faulty, it can be extracted and replaced using a schrader valve core tool.
Advantages of a Schrader valve:
- The valve is more robust because the valve core pin is inside the valve, so can’t bend.
- Because the valve has a larger diameter than a presta valve you can use a replacement tube with either valve.
The Presta valve stem is 6mm in diameter and there are different lengths to allow for rims with a deeper section but 40mm is a standard length. Just the action of the air pressure holds the inner valve body shut, however, there is also a small screw and captive nut on top of the valve body that ensures that the valve stays closed. In order to permit airflow in either direction, the valve nut must be unscrewed and depressed.
Advantages of a Presta Valve:
- They require a smaller hole in the rim, which improves rim strength.
- They’re lighter.
- They seal tightly on air pressure alone, so there’s no need for a mechanical check valve like on Schrader systems (which can clog with debris).
Overview Of Bike Valves
So, in this article we have covered everything you need to know about Bike Valves. We have covered why the inner tube has a bike valve, what the bike valves do and the two different types of bike valves; Presta and Schrader. Thanks for taking the time to read our article, we hope it has helped to improve your understanding of Bike Valves. To learn more about cycle maintenance check out our beginners courses on our Cycle Maintenance Courses page.
The purpose of Bike Valves is to control the amount of air in the inner tube. The bike valve works by allowing air to enter the inner tube, it can also close to stop this air escaping. It can also be used to allow air to leave the inner tube.
What are the 2 types of bike valves?
There are two different types of standard Bike Valves, Schrader and Presta. Schrader valves are more robust and have a larger diameter than a Presta valve. A Presta valve requires a smaller hole in the rim, thus improving the rim strength and they’re lighter.
There are advantages and disadvantages of the Presta Valve and the Schrader valve. The advantages of a Presta valve is that they’re great or skinny road bike tyres because they’re lightweight and require only a small hole in the rim improving the rim strength. The Schrader valve has a larger diameter than a Presta valve making it more robust.