I had a slow puncture and it wasn’t from my tyre?
I had just pumped my tyre up. When I disconnected the foot pump, I noticed air was escaping. I placed my finger over the end of the valve and could hear the noise change as I moved my finger (from the escaping air). On closer inspection, I found that the valve was leaking.
This article applies to most wheels (or things) that are filled under pressure via a valve stem and a Schrader type valve… I.e. Cars, vans, trucks, motorcycles, wheelbarrows, bicycles, bikes, refrigeration, air conditioning systems, etc, etc.
It’s easy to change a wheel valve core (with the aid of a valve tool). Sometimes it can be a bit stiff to undo, but this is usually when the valve cap has gone missing…
Be careful with tyres… A tyre is a pressurised container. Any damage, or incorrect repair can cause a sudden loss of air which could be dangerous at speed (a blowout). Therefore please take care (any work you may carry out is at your own risk).
What to look for?
We can test the valve and valve stem with some soapy water (as long as there is some air in the tyre).
To remove a wheel valve, you need the following:
If you’re lucky, you can sometimes remove a valve core with long nose pliers, a small screwdriver, or make your own tool. However, the tool is inexpensive and you’re more likely to have success with the correct tool for the job…
Replacing a valve is straightforward and only requires an inexpensive wheel valve removal tool. There are a few different looking valve tools available. Usually, the only difference between them is the number of added features.
If you’re lucky, you may already have a wheel valve core removal tool. Sometimes you can find the tool included with air pumps and tyre pressure gauges. The image below shows a wheel valve removal tool on the end of a tyre pressure gauge.
The steel tools are usually a lot more robust than the plastic items. In the image below, the plastic tool is starting to get a bit chewed up…
As long as you have the tyre valve tool, it’s an easy task to replace the valve.
What Are We Trying to do?
The inside of the valve stem has a thread which the valve screws into. To remove the valve core, you have to unscrew the valve. The center of the valve (the round bit in the middle) passes through a hole in the valve tool, allowing the tool to grip the two flat edges (see the image below), and undo the valve.
The image shows an 8mm Schrader type valve fitted to a bicycle inner tube.
Removing the valve:
Let any remaining air out of the tyre. So the valve core doesn’t shoot out under pressure (when undone)…
If defective, do not try and repair the existing valve! Failure (a sudden loss of air) could be dangerous at speed (a blowout). Always replace with a new valve.
There is usually only one type of valve fitted to an air filled wheel. A Schrader valve. Whereas with bicycles, there are two types, Schrader and Presta (Presta is smaller, for narrow bicycle wheel rims).
|Wheel Valve Types|
The length of the valve stem is specified using the following references (see the table below):
|Wheel Valve Stems|
|Tire & Rim No.||Length|
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