valve nut ?

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.

My physics project at NVCC: Google Groups, then
"dgoncz" and some of: ultracapacitor bicycle
fluorescent flywheel inverter

4-1-9 Fraud
secretservice.govelectronic evidence.shtmlOpen ↗

Mathias Koerber said:

A quick question regarding the nut which is used to lock
the valve against the rim.

Quoted message said:

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.

Quoted message said:

I also remember to have read elsewhere that that nut being
tight during riding might result in a tube tearing at the
valve-stem.

Quoted message said:

So, what the deal? Is that nut required/beneficial or a
problem for
a) normal riding and b) during pumping?

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 [email hidden]

Doug Goncz said:

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.

Quoted message said:

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 [email hidden]

Mathias Koerber said:

A quick question regarding the nut which is used to lock
the valve against the rim.

Quoted message said:

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.

Quoted message said:

I also remember to have read elsewhere that that nut being
tight during riding might result in a tube tearing at the
valve-stem.

Quoted message said:

So, what the deal? Is that nut required/beneficial or a
problem for
a) normal riding and b) during pumping?

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 [email hidden]

Mathias Koerber said:

A quick question regarding the nut which is used to lock
the 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?

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

A Muzi said:

Quoted message said:

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 bike.terrymorse.combike.terrymorse.comOpen ↗