I have only had this with a motorcycle wheel.
The solution was to drill (or file out) the hole to make it bigger, and drop the new valve in.
Note: - this solution will be permanent, there is no going back.
You will need to round off the edges to prevent the rim damaging the valve stem.
You need to make sure there will be enough strength left in the wheel rim, once the hole has been enlarged.
The other, less risky solution is to buy a replacement Foss tube.
Apparently they are the blue ones on the UDC website.
The UK shop has a full range in.
I have the same issue, but with the Nimbus rim.
I tried to cut down the rubber around valve of the non-Foss inner tube. Just as much that I was able to inflate air.
The inner tube is not laying correct in the rim’s bed, bot it works. I have already ordered a Foss tube, and it is ready to be replaced. But for now I use it as it is, but I know that it could explode because of the non correct laying inner tube around the valve.
I did have a look at the tube earlier, and decided to hack more rubber off. With a bit of force I managed to get the tube stem through the hole, get the tyre on and inflate it.
So hopefully be able to get it fully up and running in the near future
This comes up from time to time, and I blame Coker. Inner tubes for car and motorcycle tires (the ones that use tubes) have a thicker layer of rubber around the stem than standard for bicycle tubes. Coker’s main business is in reproduction tires for old cars and motorcycles, and when they introduced 36" tires, tubes, and rims, they used that kind of thick stem. Everyone’s been stuck in between since then, sometimes using one size and sometimes the other.
If you got it to fit then you should be good to go.
I would just use a 29’er tube. I ran one in my 36er and never had an issue. It is much, much lighter than the standard 36’er tube, and has a standard bicycle valve size so it should fit with no trouble in the rim.
+1 on this solution. If you use the Schwalbe tube, the valve stem is threaded all the way to the tube, which means it’s more secure in the hole (with the supplied jam nut). These aren’t easy to find, but since I see you’re in the UK, I get them from Chain Reaction Cycles (there in the UK).
My Qu-Ax 36er has a massive valve hole, plenty big enough to fit in these 36er tubes with the big rubber collar round the valve (my 36er came with a tube with this, and while it took a bit of wiggling, it DID come through the rim).
In fact, the hole in my rim is so big that i first pack it with an old inner tube slice before putting my FOSS tube in to make sure the FOSS doesn’t blue out through the valve hole. Isn’t yours the same?
When I got my new Nimbus rim I used the old tire and tube and had the same issue. Truth be told I like the rubber tubes better.
I was successful in trimming off enough rubber with a razorblade to get the tube through properly, The tubes have a metal shaft running down the valve, so you can take off pretty much all of the rubber down to a certain point, but it takes patience and tactfulness, because you don’t want to go too too far down the shaft and cut into the tube.
Find a friend with patience that likes to cut things. : )