[Land-speed] Tire Valves II

[Kirkwood]

Dave I agree with you about the pipe thread. But the principal reason for
using it is to provide a POSITIVE mechanical joint with no leak path! So we
need to weigh your observation with the merits of both designs. Other steel
valves have a rubber grommet sealing the pressure as well as LOCATING the
stem in the hole! I'm sure there are different designs but in the ones I
have seen, the steel stem is surrounded by rubber in the hole. There is no
stiffness provided by metal-to-metal contact of the stem in the hole. The
stiffness comes from the clamping force provided by the nut on the valve
stem. JT, that nut usually has only about 4 or 5 threads on it! So the
question Dave raises would be an interesting test. Hitting the pipe thread
with enough force will cause a certain failure. But, in a pressurized tire,
hitting the rubber-located stem with the same force might cause a
catastrophic leak and failure as well.  Also, (depending on which side of
the rim the nut is located) the centrifugal force could be working AGAINST
that nut with only a few threads on it! I'm not criticizing either design .
. . just thinking out loud here and trying to understand all the issues.
Continued comments are encouraged and . . . thanks in advance.    :-)