Replacing incorrect (too large) Metal Stem with Schrader 777?

[CudaMan]

All of the metal stem tubes that I currently have for my 1924 have the incorrect (too large) Schrader 725 size stems. I have enough of the correct Schrader 777 stems and hardware to switch over.

I've seen how folks modify rubber stem tubes to use the Schrader 777 or 888 stems, but has anyone tried the conversion on the currently available metal stem tubes? I worry that with the rubber vulcanized to the metal stem that I won't be able to cut out the incorrect stem without tearing the rubber.

[Steve Jelf]

Yes you can. I had one of the current metal stem tubes and the stem was too damaged to keep. I was able to dig it out and install an old metal stem. I was a bit surprised at the small base of the modern stem.

[CudaMan]

Thanks for the reply, Steve. That gives me confidence to give it a try on one of my spare tubes.

[CudaMan]

Well Steve, you're right, the base on the vulcanized metal stems is pretty small, see attached pic.

Unfortunately, the knife slipped a bit while I was digging this one out and the tube is ruined.

Now that I know the size hole to shoot for, I can use a gasket hole punch to cut the minimum size hole needed to remove the old stem without risking the surrounding tube material. Hopefully the correct size hole punch will be tall enough to fit over the stem and reach the tube rubber.

I suppose an alternate approach would be to just buy rubber stem tubes to modify and sell my metal stem tubes. Maybe I could get enough money for them to cover the cost of buying new rubber stem tubes.

Update - My gasket hole punches are too short to reach down to the base of the stems, so I'm going to sharpen one end of a 9/16 inch brass tube and use it to cut the rubber around the vulcanized stem.

[CudaMan]

Another update - the hole left in the tube after removing the too-large 725 size metal stem is larger than the shank of a 777 stem (no surprise). This makes me worry that a 777 stem might not seal the hole perfectly.

So, I have ordered a couple of rubber stem tubes from Universal Tire and will try modifying those for 777 metal stems. I will switch over two tires at a time as I wear tires out, so it may take a while to switch over completely.

[Mark Osterman]

Why not patch the larger hole with some thicker rubber. This way you could punch the hole in the patch before installing.

[Steve Jelf]

So, I have ordered a couple of rubber stem tubes from Universal Tire

Hartford, Custom Classic, or other? There was a run of Custom Classics that were prone to splitting. I don't know if any of those are still in the supply chain, but for now I'm sticking with Hartfords.

[CudaMan]

Universal Tire's website doesn't mention the tube manufacturer, so I'll let folks know when they arrive.

Regarding patching the hole with more rubber and cutting a new hole, sounds too scary to me, I'll let someone else try it and report back.