valve nut ?
Mathias Koerber
valve against the rim.
The other day I observed that a local LBS mech installed such a nut
onto a wheel which had none and tightened it before pumping the
tire, then removed the nut again.
I also remember to have read elsewhere that that nut being tight
during riding might result in a tube tearing at the valve-stem.
So, what the deal? Is that nut required/beneficial or a problem
for a) normal riding and b) during pumping?
just curious
Doug Goncz
the nut, pump it up a bit, let it go empty, fill it, and remove the nut.
What happens to cause a tube tear is the continuous one-way traction on the
tire when it is not maintained. At too low a pressure, the valve will tilt,
then tear. If you notice the tilt, you can avoid the tear. Thus, remove the nut
to provide an early warning of LTP.
My physics project at NVCC:
Google Groups, then "dgoncz" and some of:
ultracapacitor bicycle fluorescent flywheel inverter
4-1-9 Fraud
http://www.secretservice.gov/electronic_evidence.shtml
jobst....@stanfordalumni.org
I don't know what this mechanic had in mind, but the stem nut has been
made the scapegoat for a manufacturing flaw of tubes from which their
brass stems separate from the tube and leak. Many riders are loathe
to place blame where it belongs on the tube and believe they caused
the leak by tightening the stem nut too tightly. Therefore, how tight
should it be? The result is that the nut gets removed entirely.
When a tire is inflated to more than 100 psi, the nut is usually loose
even if it was tight when the tire was flat. It's main purpose is to
keep the stem from submerging into the rim when the tire is flat. For
users of pumps that clamp onto the stem, this may not be a problem but
racing pumps (that are becoming rare) with push on pump chucks, the
stem nut is a great assist in tire inflation.
Although there have been episodes of stem separation, the stem nut
does not them although that is most likely what is behind the action
you saw. Those who have had a few years of experience with these
things will recall that no such failures occurred over many years,
even though the stem nuts were always used (push-on pump chucks) and
then suddenly there were some stem separations. Currently there are
none, the bad ones having moved through the market.
Should we then, forever after, shun the dread valve stem nut? I still
use a pump with a Campagnolo pump chuck and don't plan on tossing the
nut.
Jobst Brandt
jobst....@stanfordalumni.org
jobst....@stanfordalumni.org
> It pulls the stem in so it's seated right during pumping. Ideally,
> you tighten the nut, pump it up a bit, let it go empty, fill it, and
> remove the nut.
> What happens to cause a tube tear is the continuous one-way traction
> on the tire when it is not maintained. At too low a pressure, the
> valve will tilt, then tear. If you notice the tilt, you can avoid
> the tear. Thus, remove the nut to provide an early warning of LTP.
If there is tire creep on a fat tire, it will tear the tube anyway,
creep not coming in small increments. There are tire anchors for
this, something dirt motorcycles have used for a long time. However
for road bicycles, tire creep requires riding a tire so flat that it
will roll in the next curve. You can easily prove that road tires
(over 50 psi) don't creep by marking a line at the rim joint on the
tire with a ball pen. Tubes do not creep within tires.
Jobst Brandt
jobst....@stanfordalumni.org
jobst....@stanfordalumni.org
I don't know what this mechanic had in mind, but the stem nut has been
made the scapegoat for a manufacturing flaw of tubes whose brass stems
separated from and cause leaks. Many riders are loathe to place blame
where it belongs, on the tube, and believe they caused the leak by
tightening the stem nut too much. Therefore, how tight should it be?
The result is that the nut gets removed entirely.
When a tire is inflated to more than 100 psi the nut usually is loose
even if it was tight before inflation. It's main purpose is to keep
the stem from submerging into the rim when the tire is being inflated.
For users of pumps that clamp onto the stem, this may not be a problem
but racing pumps (that are becoming rare) with push on pump chucks,
the stem nut is a great assist in tire inflation.
Although there have been episodes of stem separation, stem nuts do not
cause them although that is most likely what is behind the action you
saw. Those with a few years experience with tires will recall that no
stem separations occurred over many years, even though the stem nuts
were always used (push-on pump chucks) and then suddenly there were
some stem separations. Currently there are none, the bad tubes having
been used up.
Should we then, forever after, shun the dread valve stem nut? I still
use a pump with a Campagnolo pump chuck and don't plan on tossing the
stem nut.
Jobst Brandt
jobst....@stanfordalumni.org
A Muzi
We remove them in assembly and in service without exception,
unless customer requests them.
--
Andrew Muzi
www.yellowjersey.org
Open every day since 1 April, 1971
Terry Morse
> > So, what the deal? Is that nut required/beneficial or a problem
> > for a) normal riding and b) during pumping?
>
> We remove them in assembly and in service without exception,
> unless customer requests them.
And the reason for this service behavior is?
--
terry morse Palo Alto, CA http://bike.terrymorse.com/