Original Equipment tire valve stems on dually

[Big Rig]

I tried to check the air on the dual wheels & I found that I can't get a reading. It looks like there is a 2 inch plastic extension screwed into the tire valve. (I think) It has a little plastic "tit" on the end that you can push down but no air comes out. I can't get any reading when I put the gauge on it.

What is this plastic thing? What am I doing wrong? Should I be getting a pressure reading out of it? This really makes me feel stupid.

The front wheels have a regular valve that lets me check the pressure.

Big Rig

 

[Eric_77]

Get the plastic ones off they are not rated for the pressures of a dually, used to be common back in the hubcap days to extend the valve past a hubcap have not seen them(steel version) except on dual wheel rigs (mainly semis) I would bet the dealership added them. If you go to a truck tire store you should be able to get the steel versions if you want them, they are handy on the semi where I check tire pressure every day.