with RV tire expert Roger Marble
As a follow-up to last week’s post of why I recommend people NOT use rubber valve stems with their external TPMS sensors, I decided to show some of the “guts” of valve stems.
Standard “rubber snap-in” stems like the TR413. If you look down the hole you can see the end of the brass part of the stem. More on this later.
These have been used for decades on hundreds of millions of tires. These can be installed by hand using a “puller” that stretches the rubber which makes the diameter of the stem small enough to “snap” into place in the wheel hole.
Once installed, the wheel “pinches” the rubber part of the stem to seal the air in. The arrows show the location of the wheel relative to the metal part of the stem. Note the part of the valve stem that goes into the air chamber was cut off before I took this picture.
You can see that the brass stops before it gets past the edge of the wheel. This makes installation easier.
Next, we have the “High Pressure” stems such as the HP-500.
Now when we look at a “bolt-in” stem, like this TR416s, we see the location of the wheel hole at the arrows.
I am also including pages from the U.S. Tire & Rim Association (TRA) yearbook which publishes the “interchange and fitment” specs so all tire companies and valve manufacturers know what dimensions are required.
This is the book where all the load and inflation tables come from and might be considered the Tire Engineer’s “Bible.” It is used by tire engineers around the world when they are making tires that are intended to be used in the U.S.
Here we find the details of valve stem designs as specified by TRA.
Finally, to show the attention to detail, here is the spec for the little pin that sticks out of the valve stem. Not meeting this specification could be the reason your TPMS does not register your tire pressure. (Yes, I have run into that problem.)