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  #1  
Old 23-10-19, 20:33
Russell Boaler Russell Boaler is offline
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Location: Wellington, New Zealand
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Default 1100 - 20 tubes

I'm struggling to find a set of tubes suitable for 20 inch CMP rims here in NZ. I've tried several different local firms and the only tubes that they seem to be able to come up with have a 180mm long valve stem. That'll protrude way too far beyond the edge of the rim. My assessment is that the right valve stem length would be in the region of 80 - 100mm.
Has anyone got a recommendation of where to get tubes from which have a suitable valve stem length? At this stage I'm thinking somewhere in either Australia or the UK only because it's a bit more convenient for me to ship from there.

Thanks
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  #2  
Old 23-10-19, 21:32
Phil Waterman Phil Waterman is offline
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Default Do they have screw on stems

Hi Russell


Do they have screw on valve stems out your way? Last time I was buying new tubes had the same issue. Then one of the heavy truck tire outfits suggested tubes with screw on stems. They had to order the tubes and the stems but they had them in pretty short order. But they have worked fine. I don't remember the brand but it was of better known brands.


The ones in my picture are the long stems, the ones they got me were about half the length. They also had them longer.


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Cheers Phil
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  #3  
Old 24-10-19, 01:44
Russell Boaler Russell Boaler is offline
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Default

Thanks Phil.
Whereabouts does the screw connection actually occur? Is it at the connection point to the outlet from the tube itself?
One supplier did mention the option of screw on valve stems but at the time what was described to me (albeit second hand) was that the original stem was cut off after the bend and the the remaining stem threaded, then a suitably short stem extension was attached to it. I didn't like the sound of that not knowing how big the outer diameter of the screwed on extension was going to be. If it was too big it would mean the valve stem wouldn't sit nicely in the formed recess in the rim potentially causing stress on the screwed connection.

Russell
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  #4  
Old 24-10-19, 05:17
Paul Singleton Paul Singleton is offline
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Default Valve stem

When I serviced truck tires in the 80’s there were still a lot of tube type tires, mostly 16 and 20 inch. Most of the 20” tubes had a brass nut vulcanized into the tube and the valve stem screwed in and the jam nut allowed the stem to face whatever direction you needed. I also remember putting truck tubes into farm equipment and swapping to straight valve stems because the truck stems were too long and stuck out past the rim. With the popularity of tubeless tires, I don’t know what would be available today for tubes or valve stems.
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  #5  
Old 24-10-19, 14:15
Phil Waterman Phil Waterman is offline
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Default Tub has short brass stub

Hi Russell

Yes the tube is made with a brass stub, which the valve stem screws on to.

At that time the problem I had was finding a truck tire place that was willing to take the time to find them. Several places just wanted to sell me the tubes they had in stock, which all had long stems. The place I got them is still in business, so next time I drive bye will stop in and ask if they are still available and who makes them.

Cheers Phil
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  #6  
Old 10-11-19, 19:30
Russell Boaler Russell Boaler is offline
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Default Some progress

I've made some progress on this. Screw-on replacement valve stems of assorted sizes/lengths are available as previously suggested. You need to cut the original valve stem off at the base just above the thread that secures the metal sheild. The replacement valve stem is then screwed onto this thread. There's a rubber washer that goes between the face of the replacement valve stem and the tube to create an air tight seal.

The down side for me at the moment is that the only replacement valve stems that my local tyre guy can locate at present are those used on earth moving equipment. They are a much bigger diameter than the standard valve stem (for increased airflow)... as can be seen in the attached slightly blury photo.

A quick check of the dreaded ebay suggests normal size screw on replacement valve stems are readily available from the US. Will do a bit more research but importing some replacement valve stems is probably going to be the solution.
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valve stem1.jpg   valve stem.jpg  
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  #7  
Old 20-02-20, 19:14
Russell Boaler Russell Boaler is offline
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Default problem solved

In the end I bought some valve stems off ebay which are available out of the USA.

It was a fairly simple task of cutting off the old stem and screwing on the new stem. I fitted a rubber washer between the new valve stem and tube to give more flexibility on valve position when fully screwed down and applied a liberal amount of sealant over all joints. I wasn't sure what the best sealant was to use so, as I had some gasket silicone on the shelf, used that. In hindsight it might have been better with a locktite product but we'll see how they go.... can always remove them and re-seal them if there is ever a problem.

I used the 4 inch long valves stems. These are possibly still a bit long as they put the end of the valve stem roughly in line with the face of the rim. There are also 3 1/2 inch and 3 inch options available.

Perhaps this post would now be better in the softskin forum or similar for future reference?
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valve stems.jpg   valve stem 1.jpg   valve stem 2.jpg  
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