Make a hole on the rim with 75 to 80 drill bit. For the valve itself you can use a small spring from an old watch or you can make your own.

Here’s how:

1. Roll wire around a mini tube or other wire that is the diameter you need, or you can use plastic tube with knife cuts to simulate the spiral pattern on the valve.
2. Next, insert a small piece of wire or tubing into your original larger tube.
3. Now glue the entire assembly into the hole you drilled in the rim.

The result is a beautiful replica of a stem air-valve which can be further enhanced with weathering.