Presta valve separating from tube
Bob Comiskey
time in a couple of weeks, third time recently. The tubes were all
Specialized 700x20-28, labeled "thin" on the tube itself.
This could be a run of bad tubes, as all three were bought at the same
time, or a run of bad luck. But I wonder-
I use a Silca track pump with the brass bell chuck and the rubber
grommet. This chuck takes a lot of effort to remove from the stem, and I
wonder if this is causing or accelerating the problem. (The rim looks
okay at the hole.) Any opinions?
Alternately, is there a good Silca pump with a thumb lever chuck instead
of a brute force chuck?
BC
Jobst Brandt
> The valve separated from the tube as I removed the pump chuck. Second
> time in a couple of weeks, third time recently. The tubes were all
> Specialized 700x20-28, labeled "thin" on the tube itself.
Don't let anyone tell you it's user error. These are faulty tubes and
should be returned to the shop they came from. How else are we going
to let the MFG know that the product is faulty. This happens much too
often to be ignored. Classically the brass stem comes out of the
reinforcement pad on the tube with a slight coating of rubber, but
sometimes even clean. This is a production control problem that can
be fixed, but only if there is some feedback from users.
I carry an old screw-in type stem from tubulars in my patch kit that
enables me to continue to use the tube when this happens on the road.
Latex tubular tubes all had screwed on stems because you can't
vulcanize metal to latex rubber.
Jobst Brandt <jbr...@hpl.hp.com>
A Muzi
your Silca wire clip is loose). Maybe you should adjust the cap of your
Silca. Unscrew for less bite, turn tighter as the washer wears.
Bob Comiskey wrote:
> The valve separated from the tube as I removed the pump chuck. Second
> time in a couple of weeks, third time recently. The tubes were all
> Specialized 700x20-28, labeled "thin" on the tube itself.
>
> This could be a run of bad tubes, as all three were bought at the same
> time, or a run of bad luck. But I wonder-
>
> I use a Silca track pump with the brass bell chuck and the rubber
> grommet. This chuck takes a lot of effort to remove from the stem, and I
> wonder if this is causing or accelerating the problem. (The rim looks
> okay at the hole.) Any opinions?
>
> Alternately, is there a good Silca pump with a thumb lever chuck instead
> of a brute force chuck?
>
> BC
--
Yellow Jersey, Ltd
http://www.yellowjersey.org
http://www.execpc.com/yellowje
Open every day since 1 April, 1971
A Muzi
but you're right- nothing the cyclist does should pull a valve out of a
tube.
Jobst Brandt wrote:
> Andrew Muzi writes:
>
> > You can put a thumblock type head on your Silca (add a 95c hose
> > clamp if your Silca wire clip is loose). Maybe you should adjust
> > the cap of your Silca. Unscrew for less bite, turn tighter as the
> > washer wears.
>
> As I said, it's not operator error but faulty tubes. Therefore,
> advice on how to prevent stem separation is misplaced.
>
> Jobst Brandt <jbr...@hpl.hp.com>
Jobst Brandt
Bob Comiskey
the cause of this problem. I replied that I have never used them, but had
not had the problem until recently. I don't understand what the nut will do
for me. It would keep the stem from being jammed into the tube and rim, but
would not keep the stem from being pulled out of the tube.
What is the purpose of the nut? Does everyone else use them?
BC
spinner
using them and it will be a long time before I give them another shot.
I was foolish and did not return the tubes to shop I bought them at. I
hope that you do and get replacements from another manufacturer.
In article <39DB9B37...@mediaone.net>,
bobco...@mediaone.net wrote:
> The valve separated from the tube as I removed the pump chuck. Second
> time in a couple of weeks, third time recently. The tubes were all
> Specialized 700x20-28, labeled "thin" on the tube itself.
>
> This could be a run of bad tubes, as all three were bought at the same
> time, or a run of bad luck. But I wonder-
>
> I use a Silca track pump with the brass bell chuck and the rubber
> grommet. This chuck takes a lot of effort to remove from the stem, and
I
> wonder if this is causing or accelerating the problem. (The rim looks
> okay at the hole.) Any opinions?
>
> Alternately, is there a good Silca pump with a thumb lever chuck
instead
> of a brute force chuck?
>
> BC
>
>
--
"It does not get any easier, you just get faster." - Greg Lemond
Sent via Deja.com http://www.deja.com/
Before you buy.
John Everett
>
>What is the purpose of the nut? Does everyone else use them?
>
No, in fact the tubes I use (Michelin Ultra Lights) don't even have threads on
the stems for the useless little nuts.
--
jeverett<AT>wwa<DOT>com (John Everett) http://www.wwa.com/~jeverett
dvt
news:39DC73FF...@mediaone.net...
>
> What is the purpose of the nut? Does everyone else use them?
They make it a little easier to slip the pump head on the nozzle when the
tire is completely deflated. That's about it.
Dave
dvt at psu dot edu
Jobst Brandt
> I got an email suggesting that if not using a locknut on the stem might be
> the cause of this problem. I replied that I have never used them, but had
> not had the problem until recently. I don't understand what the nut will do
> for me. It would keep the stem from being jammed into the tube and rim, but
> would not keep the stem from being pulled out of the tube.
> What is the purpose of the nut? Does everyone else use them?
The nut is there for the user, not the tube. Long ago, in ancient
times, riders inflated tires with frame fit pumps that had a simple
valve chuck (pump head) rigidly affixed to the pump. This pump was
held on the valve stem with one hand serving as stator into which the
other hand pumped. The jam nut prevented the valve stem from wobbling
and receding into the rim.
Today, modern bicyclists use CO2 cartridges or use their cell phone to
call for a ride to a bicycle shop to re-inflate tires, so the jam nut
no longer serves any purpose.
Jobst Brandt <jbr...@hpl.hp.com>
Mike Hauptman
others although I don't know what brand of tube they were using. It was when
the person was using a frame pump to inflate the tire and didn't keep both
hands on the pump, they placed one hand on the pump handle and instead of
holding the pump body they placed their other hand on the rim to offset the
pump action.
my $.02
Mike Hauptman
Bob Comiskey <bobco...@mediaone.net> wrote in message
news:39DB9B37...@mediaone.net...
Helmut Springer
> Today, modern bicyclists use CO2 cartridges or use their cell
> phone to call for a ride to a bicycle shop to re-inflate tires, so
call me old fashioned then, but I sure did some cursing about the
nutless tubes on a touring bike this summer. a frame fit pump with
a lockable small tube isn't a bad thing though, prevents you from
applying unwanted force to the valve stem while pumping and makes
things easier for people with less arm strength.
--
MfG/best regards, helmut springer
de...@FaVeVe.Uni-Stuttgart.DE
"Freedom's just another word for nothing left to lose"
Matt O'Toole
"spinner" <linc...@my-deja.com> wrote in message
news:8rhtas$v8p$1...@nnrp1.deja.com...
> Last year I had two specialized tubes do the same thing to me. I stopped
> using them and it will be a long time before I give them another shot.
I've had three do it in the last couple of years. The stems came out clean
each time. At first, I attributed it to using a Presta tube with a Schrader
rim. But it shouldn't make a difference. The hole is bigger, but not
*that* big.
> I was foolish and did not return the tubes to shop I bought them at. I
> hope that you do and get replacements from another manufacturer.
My foolishness was buying them at Sea Schwinn. Any trip in there takes at
least half an hour. First, you have to interrupt the staff's nose-picking
session to get some help (which they really hate, so then you'll have to
deal with their attitude). Then you have to wait for the manager to come
out to help them deal with their ancient, dysfunctional cash register sytem.
All the while, you can feel the blood pressure of the people in line behind
you rising to stroke level. All in all, a pretty intimidating experience.
And that's just to buy something. I can't imagine what a return would be
like.
Matt O.
Steve
Why not just connect your Visor/Palm to the value.
Steve Evans
Jobst Brandt wrote:
> Bob Comiskey writes:
>
> > I got an email suggesting that if not using a locknut on the stem might be
> > the cause of this problem. I replied that I have never used them, but had
> > not had the problem until recently. I don't understand what the nut will do
> > for me. It would keep the stem from being jammed into the tube and rim, but
> > would not keep the stem from being pulled out of the tube.
>
> > What is the purpose of the nut? Does everyone else use them?
>
> The nut is there for the user, not the tube. Long ago, in ancient
> times, riders inflated tires with frame fit pumps that had a simple
> valve chuck (pump head) rigidly affixed to the pump. This pump was
> held on the valve stem with one hand serving as stator into which the
> other hand pumped. The jam nut prevented the valve stem from wobbling
> and receding into the rim.
>
> Today, modern bicyclists use CO2 cartridges or use their cell phone to
Jonathan Madden
If the locknut is tightened even a little when the tube/tyre is fully
inflated, then as the tube gradually defleates over days/weeks before the
tube is pumped up again a significant force builds up between the locknut
and the valve/tube seat. Likewise if you have a puncture, or simply deflate
the tube, the same thing will happen. The valve will then in time tend to
separate from the tube.
To avoid this, keep the locknut (if you use one) slack at all times.
Jonathan Madden
<jonm...@yahoo.com>
Jobst Brandt
> A lock nut can contribute to separation of the valve from the tube.
Not unless you tighten it with tools. Finger tightening does not
generate enough force to do anything to a stem that is properly
vulcanized into the tube.
> If the locknut is tightened even a little when the tube/tyre is
> fully inflated, then as the tube gradually defleates over days/weeks
> before the tube is pumped up again a significant force builds up
> between the locknut and the valve/tube seat. Likewise if you have a
> puncture, or simply deflate the tube, the same thing will happen.
> The valve will then in time tend to separate from the tube.
I think you'll have to describe what causes this effect. The stress at
the stem to rubber interface does not change when inflated or flat at
any given position in the rim recess for the stem. The nut only holds
that position and makes pumping easier.
> To avoid this, keep the locknut (if you use one) slack at all times.
Sounds like another one of these arcane sufferances invented in the
theme of "no pain no gain" and the more tedious the exercise the
greater the merit. I don't buy it. How do these urban legends get
started? They pop up faster than they can be swatted with a fly
swatter.
Jobst Brandt <jbr...@hpl.hp.com>
Jonathan Madden
Just my experience. I've noticed on several occasions that a racing tyre
pumped up to 100 psi (with the locknut finger tight after inflation -
that's the mistake, of course) causes the locknut to become much tighter as
the tyre gradually deflates.
And then the valve pulls out sometime later - I've had this happen three
times over the last year. Now I do without the locknut, of just leave it
slack after pumping.
No further problems - just the same number of punctures around London, but
at least I can repair these.
Jonathan Madden
Jobst Brandt
> Not a myth - yet.
What are you getting at?
> Just my experience. I've noticed on several occasions that a racing tyre
> pumped up to 100 psi (with the locknut finger tight after inflation -
> that's the mistake, of course) causes the locknut to become much tighter as
> the tyre gradually deflates.
> And then the valve pulls out sometime later - I've had this happen three
> times over the last year. Now I do without the locknut, of just leave it
> slack after pumping.
I don't know how long you have been riding but I've been at it long
enough to know that this is a recent phenomenon and I have not changed
the way I install tubes with lock nut in at least 40 years. Your
statistic of a stem failing with lock nut twice is not convincing,
especially when there was no control. As far as can be established
from what you experienced, we can say that those tubes failed. We
don't know whether they would not have failed without a lock nut
because I have had contrary results. Always using a lock nut, more of
my tubes do not have this failure and the ones that don't get
inflated every three or four weeks unless I get a flat. Then they get
inflated by the stem removing frame pump and don't fail either. The
ones that fail are usually ones that have no more than one patch.
> No further problems - just the same number of punctures around
> London, but at least I can repair these.
So in so many words, you are ready to say it is an operator error
rather than manufacturing error.
Jobst Brandt <jbr...@hpl.hp.com>
Jonathan Madden
valve/stem failures.
I too have been cycling for ages, but only in the last year or so have I started
to use high pressure narrow tyres, e.g. 700C 22s etc. The lighter construction of
the tubes for these tyres makes them more fragile and, I suppose, less able to
withstand movement and stress around the valve than heavier-duty tubes. I might
also have further exacerbated things by pumping up the tyre without first
slackening off the locknut after it has become tight through deflation, and
thereby causing stress around the valve seat while the joint is under tension.
Anyway I believe I have found the reason for the tube failures I have had
recently (with more than one make of tube), and which I now seem to have
prevented. Lock nuts certainly make inflation easier, especially with a
conventional portable pump.
Jonathan Madden