Removing Rubber Stem from Tube

[Tadpole]

My first go around with putting original metal stems into a modern tube. What’s the best way to pull the old brass core out now that I’ve cut off most of the rubber valve stem? There’s a fair bit to grab on to but it’s bonded to the tube very well. Wanted to ask the experts before I goof.

[Humblej]

You have to cut closer to the tube.

[CudaMan]

The stem appears to be recessed down into a pocket on the tube, what brand of tube is it?

On mine, I cut around the base of the rubber as close to the surface of the tube as possible with a razor blade and left the top of the rubber stem intact to give plenty of surface for my pliers to grab while I twisted the stem out. Some of them can be pretty stubborn. The sharpened brass tube idea used in the linked page looks pretty good also, although I have never tried it.

Once the metal stem is out, I used my small pneumatic angle grinder with an abrasive "cookie" to smooth the surface of the tube.

https://www.sheepisland.com/cars/tech/metal_stems/

[Original Smith]

What have you done to that tube? It looks like you have a bunch of rubber cement around the area where he stem used to be. It should be clear, and only the portion of where the stem used to be. Only then can you start smoothing the area for the original stem. It may take some time. I usually start with a file, and then go to sand paper. Sometimes the brass core doesn't want to come out easily and you have to tweak it several times to get it to let loose.

[Tadpole]

Thank you Jeff, Mark and Larry!
Mark, that link is exactly what I needed, thanks!

These are “Custom Classic” Tubes, no idea their age, took them out of old tires to practice mounting stems. There is a slight depression around the stem, which grew when I put some air to the tube. As you can see.

I hadn’t done anything to the tube except cut off most of the rubber stem. Here is another view of the same picture I first posted. And then the finished product. No leakage so far. I’ll let it sit for a week and see.

[Humblej]

Good job. Welcome to the do it yourself stem club.

[Allan]

I leave the rubber stem stem intact when making the cut around the base. As mentioned, that leaves you something to grip when working the base out of the tube after making the cut. I also make the cut 1/8" or so up from the bottom as shown in the last photo. You may have to 'Work' the cut stem to break the last contact on the brass core to get it out.
Nothing makes the job of roughing down the stem easier than the mushroom shaped tool the tyre shops use make repairs. Rather than make the area dead flat and smooth, I leave a ridge of the rubber stem around the hole. This extra rubber fits neatly inside the depressed ring around the bridge washer, giving the washer more rubber to squish when making the seal. Old style tubes had a thicker pad of rubber at the valve stem hole. Some even had cloth fibre reinforcement in the rubber.
Hope this helps
Allan from down under.