Problems With TR83A Valve Stems

John

John

Senior Member
I recently purchased several repro TR83A metal valve stems from a major Model A supplier to install in my 19 inch tubes. Upon installation, I found that the valve cap ordered at the same time would not fit on the valve stem. I thought that it would not be a problem until the person who mounted the tires found his air nozzle on the tire changer would not fit the stems also. I then found that my portable air compressor would not fit the thread on the stems. I measured the thread diameter of the stems and found it significantly oversize. I then purchased the proper thread die for the stems (try to find that thread series) and rethreaded the stems. The die cut quite a bit off the threaded area proving that the stem was oversize. I checked an old reproduction valve stem and did not have the oversize thread problem.

Was it just my luck with these 4 stems or am I missing something here? Anyone else have this problem?

John
 
The thread is an external 8V1 thread: 0.305 in (7.747 mm) x 32 TPI (1 ⁄ 32 in or 0.7938 mm pitch; tap size 8v1-32). Note that this is not a standard metric or USA thread. It is a standard Schrader valve stem thread. Even my original Acme Model A valve stems have this thread. The threading die is available on weebay and possibly Amazon.

John
 
I don't know if this helps, I have used Coker Item # 87010 Hartford TR127 with brass stems, I used the hardware and dust caps they sell to make them look original. Very happy with everything.
 
John said:
The thread is an external 8V1 thread: 0.305 in (7.747 mm) x 32 TPI (1 ⁄ 32 in or 0.7938 mm pitch; tap size 8v1-32). Note that this is not a standard metric or USA thread. It is a standard Schrader valve stem thread. Even my original Acme Model A valve stems have this thread. The threading die is available on weebay and possibly Amazon.

John
Click to expand...


I have original Ford drawings showing a 5/16" - 32 thread and other threads which are wrong, Ford didn't make the valve parts, only made drawings using Schrader and Dill samples to copy. The drawings show both valves beside each other. They made an assumption when drawing them and didn't get it correct.

All tire valve hardware has their own proprietary sizes and tolerances just like Imperial and Metric have their own specifications. Imperial, Metric and tire valve threads aren't interchangeable.

The International Standard, ISO 4570, First edition 2002-03-15. The title reads Tyre valve threads. Where the valve screws into, is designated 5V1, the cap is as John says 8V1, the stem large thread is 10V2 for 1930/31 short dust cap and for 1928/29 Dust Cap 12V1.

There are reproductions made from these Ford drawings or they made the same assumptions using original parts. Along with the threads where the cap fits, some 1928/29 dust cap threads were made larger also. The dust cap will not interchange with originals but do have the corresponding reproduction parts to match their error.

When dealing with valve parts for your restoration make sure if you use some original parts that replacements will fit your parts. You may need all original parts to fit or use complete reproduction sets.

Make sure the thread for the cap is correct (same as the original) or it will not interchange with all the tire filling equipment available today along with any valve caps.
 
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Many thanks for the update. Apparently the reproductions I purchased were made from the incorrect Ford print (5/16"-32) instead of using the correct Schrader valve thread.

John
 
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