What's the deal with that Presta valve nut?

[A Muzi]

> > In article <[email protected]>, <[email protected]> wrote:
> > >>> Meanwhile, this can be fixed. I carry a spare stem from a latex tubed tubular tire in my
> > >>> patch kit. In the event of a stem separation, I remove the failed stem, insert the tubular
> > >>> stem, tighten its clamp nut and inflate the tire. I'm on my way.

> > >Joe Riel writes:
> > >> That works? What prevents the air from leaking out around the base of the inserted stem?

(JB)> > >Take a look at one of these stems. Latex does not lend itself to
> > >molding around a brass stem as butyl tubes do. Therefore, the stem essentially has a mushroom
> > >end that is forced through the hole in the

(JR)> > So do you have a source for the valve stems, or is there a particular
> > latex tube brand you buy that has the magic removable valve stem? I have had a few latex tubes
> > before but none like that.

"Karl Nelson" <[email protected]> wrote in message
news:[email protected]...
> [email protected] (Paul Southworth) wrote in message
news:<5PNma.34480$A%[email protected]>...
> I looked in vain for this kind of thing around here. Everyone pretended like I was crazy; there
> was no such thing.
>
> So I tried this: I took a regular presta stem that had separated and soldered a mushroom-shaped
> washer on the bottom. It was just a sort of half-grommet, half-washer that I found; I don't know
> what they're called. It seems to work OK. I think it may still leak a little, but it seems slow
> enough that I think I could use it in a pinch. If I knew more what these valve stems looked like,
> I could maybe improve it a little. Anyone have a picture?

http://www.yellowjersey.org/photosfromthepast/VALVE.JPG shows bolt-in Schrader and Dunlop valves. I
didn't have a presta handy that day. You can scavenge really nice ones out of dead handmade tubulars
but those are not on every strreetcorner nowadays either.

--
Andrew Muzi http://www.yellowjersey.org Open every day since 1 April 1971

 

[David Damerell]

Andrew Bradley <[email protected]> wrote:
>[email protected] wrote:
>>Oh ****!!! There are fear mongers behind every fencepost. I am sure I've been riding longer than
>>you by a reasonable bit and have not yet had one of these "disasters" or carried pliers.
>What, you mean you fit these nuts? I find it hard to believe you have not encountered this problem
>if you do

I am not quite as experienced as Jobst, but I have been riding for some time, and I do fit these
nuts because they make pump attachment a bit easier - however, I don't do them up any more than is
absolutely necessary, so when the tyre is fully inflated there's about 2/3" of valve stem between
the nut and the rim.

I have never had one of these nuts jam.
--
David Damerell <[email protected]> Distortion Field!

 

[Jobst Brandt]

Andrew Muzi writes:

>> Anyone have a picture?

http://www.yellowjersey.org/photosfromthepast/VALVE.JPG

> shows bolt-in Schrader and Dunlop valves. I didn't have a Presta handy that day. You can
> scavenge really nice ones out of dead handmade tubulars but those are not on every street corner
> nowadays either.

Take that picture again (with the Presta stem) and use matte grey paper as a background. While
you're at it how about drawing some rectangular boundaries around the valve type groups. This is a
useful resource so it's worth doing. In fact the various items might even be labeled.

Jobst Brandt [email protected] Palo Alto CA

 

[Sheldon Brown]

Andrew Bradley wrote:

>>Sound advice (apart from the ecological implications). Those nuts can get siezed on. If you're not
>>carrying pliers, preferably two sets, you will have difficulty changing the tube.

Jobst replied

> There are fear mongers behind every fencepost. I am sure I've been riding longer than you by a
> reasonable bit and have not yet had one of these "disasters" or carried pliers.

Actually, I once did run into a problem with this. A customer used pliers to _tighten_ the valve
nut. Then he got a flat. Took some pretty serious force to get the damn thing off. If mem'ry serves,
I had to resort to Vise-Grips.

The deal is that when the tube is pressurized, the valve is forced down hard against the rim,
but when it goes flat and the pressure is released, the valve retracts a bit, causing the nut to
get tighter.

Set your torque wrench to 3.14 yard/milligrams.

Sheldon "Pinkie Tight" Brown +-----------------------------------+
| The gains in life come slowly, | but the losses come suddenly. | -- Garrison Keillor |
+-----------------------------------+ Harris Cyclery, West Newton, Massachusetts Phone 617-244-9772
FAX 617-244-1041 http://harriscyclery.com Hard-to-find parts shipped Worldwide
http://captainbike.com http://sheldonbrown.com

 

[Tim McNamara]

In article <[email protected]>, [email protected] wrote:

> Andrew Bradley <[email protected]> writes:
>
> > Sound advice (apart from the ecological implications). Those nuts can get siezed on. If you're
> > not carrying pliers, preferably two sets, you will have difficulty changing the tube.
>
> Oh ****!!! There are fear mongers behind every fencepost. I am sure I've been riding longer than
> you by a reasonable bit and have not yet had one of these "disasters" or carried pliers.

I have had a couple of odd jammed-nut encounters (hmmm, that didn't sound right). The first was a
Specialized tube which had had the nut cross-threaded onto the stem at the factory and was a bear to
get off. Only time I ever saw this.

The other time, I had run over some sharp metal in a hole which was loosely covered in sand and
slashed up the tube and tire badly. I pulled out a new Continental tube- and couldn't loosen the
valve stem nut (the little one on the valve core, not the one that threads down onto the rim) to be
able to inflate it..Of course I discovered this after having installed the tube. It came from the
factory cranked down too hard or crossthreaded. Danged annoying and I think I may have said a bad
word or two about German engineering.

Now I can't remember what I did to get to the nearest bike shop- I may have swapped valve cores
between the old and new tubes or tied the old slashed up tube into a knot or something. Anyway, I
bought a new tire and a new tube; I mentioned the problem to the bike shop owner, and out of
curiosity he checked a few Conti tubes and found another one that he couldn't unscrew the valve stem
nut with his fingers. Since then I have found a few more Conti's with the valve nuts jammmed down
too tight to loosen with my fingers, fortunately in the comfort of my basement.

Now I just check before sticking them into my saddlebag- rather than dragging the weight of pliers
around with me.

 

[Tim McNamara]

In article <[email protected]>, "Matt O'Toole" <[email protected]> wrote:

> <[email protected]> wrote in message news:[email protected]...
>
> > Oh bull ****. I have had stems separate that were perfectly straight. This is a manufacturing
> > problem and some tubes have it while others don't.
>
> Every Specialized tube I've had has died this way.

Now that you mention it, I have had a spate of 26 x 1.0 Specialized tubes fail this way.

 

[Rotofool]

[email protected] (Andrew Bradley) wrote in message
news:<[email protected]>...
> "David L. Johnson" <[email protected]> wrote in message
> news:<[email protected]>...
> > On Mon, 14 Apr 2003 10:29:57 +0000, Michael wrote:
> >
>
> Sound advice (apart from the ecological implications). Those nuts can get siezed on. If you're not
> carrying pliers, preferably two sets, you will have difficulty changing the tube.

If you use the protective cap for the end of the stem the nut can be backed off until it jams
against the cap. This way the nut is always available for pumping up the tire, without any chance of
jamming or holding the base of the stem too tight against the rim. I've been using this technique
for years with no problems.

Len Thunberg

 

[A Muzi]

> >> Anyone have a picture?

> Andrew Muzi writes: http://www.yellowjersey.org/photosfromthepast/VALVE.JPG
>
> > shows bolt-in Schrader and Dunlop valves. I didn't have a Presta handy that day. You can
> > scavenge really nice ones out of dead handmade tubulars but those are not on every street corner
> > nowadays either.

<[email protected]> wrote in message news:[email protected]...
> Take that picture again (with the Presta stem) and use matte grey paper as a background. While
> you're at it how about drawing some rectangular boundaries around the valve type groups. This is a
> useful resource so it's worth doing. In fact the various items might even be labeled.

Good suggestion. I'll try to do just that.

--
Andrew Muzi http://www.yellowjersey.org Open every day since 1 April 1971

 

[Andrew Bradley]

Sheldon:

> The deal is that when the tube is pressurized, the valve is forced down hard against the rim, but
> when it goes flat and the pressure is released, the valve retracts a bit, causing the nut to get
> tighter.

This nicely explains the type-1 valve nut disaster (1 set of pliers may be enough). Problem
accentuated by the effects of cold on fingers (valve?).

Type-2 (2 sets of pliers) is where nut and valve both turn, the deflated tube offering no reverse
torque. Not sure if the type-1 explanation can alone explain this type. I've seen both types.

Something for those with charmed lives to ponder.

Andrew Bradley

 

[Tim McNamara]

In article <[email protected]>, [email protected] (Andrew
Bradley) wrote:

> Sheldon:
>
> > The deal is that when the tube is pressurized, the valve is forced down hard against the rim,
> > but when it goes flat and the pressure is released, the valve retracts a bit, causing the nut to
> > get tighter.
>
> This nicely explains the type-1 valve nut disaster (1 set of pliers may be enough). Problem
> accentuated by the effects of cold on fingers (valve?).
>
> Type-2 (2 sets of pliers) is where nut and valve both turn, the deflated tube offering no reverse
> torque. Not sure if the type-1 explanation can alone explain this type. I've seen both types.

Remove the tire, press the valve stem against the bed of the rim from the outside with your thumb,
and this should ease the tension on the nut enough for it to be unscrewed. Then next time only
lightly tighten down the jam nut.

 

[Tim McNamara]

In article <[email protected]>, [email protected]
(Chris Zacho "The Wheelman") wrote:

> Jobst Brant wrote:
>
> > Ho ho! That is not what the nut is supposed to do and creeping tires tear stems off easily."
>
> That is the purpose I always read in various publicated sources that mentioned them.
>
> What's your reason?

AFAIK, it's this. Schrader valves use either a screw-on pump head fitting or a
thumblever-compression head fitting, so you don't push much on the valve. Presta valves usually use
a press-on friction gasket pump head, so the stem retreats into the rim when you try to push the
pump head on. The jam nut is just a limiter for this.

 

[Jobst Brandt]

Tim McNamara <[email protected]> writes:

>>> Ho ho! That is not what the nut is supposed to do and creeping tires tear stems off easily."

>> That is the purpose I always read in various publicated sources that mentioned them.

>> What's your reason?

> AFAIK, it's this. Schrader valves use either a screw-on pump head fitting or a
> thumblever-compression head fitting, so you don't push much on the valve. Presta valves usually
> use a press-on friction gasket pump head, so the stem retreats into the rim when you try to push
> the pump head on. The jam nut is just a limiter for this.

The reason people need to ask is that the manual frame fit (Silca Impero) pump of old is no longer
used, nor are pumps in general. It's CO2 cartridges or mini pumps with hoses. Those who use pumps
with integral pump heads, instead of pumping into their fist, often pump against the stem, breaking
it off. This convinces them to use CO2 cartridges.

Jobst Brandt [email protected] Palo Alto CA

 

[A Muzi]

> >> Anyone have a picture?

> Andrew Muzi writes: http://www.yellowjersey.org/photosfromthepast/VALVE.JPG
>
> > shows bolt-in Schrader and Dunlop valves. I didn't have a Presta handy that day. You can
> > scavenge really nice ones out of dead handmade tubulars but those are not on every street corner
> > nowadays either.
>

<[email protected]> wrote in message news:[email protected]...
> Take that picture again (with the Presta stem) and use matte grey paper as a background. While
> you're at it how about drawing some rectangular boundaries around the valve type groups. This is a
> useful resource so it's worth doing. In fact the various items might even be labeled.

An excellent suggestion. http://www.yellowjersey.org/nuvalve.html

--
Andrew Muzi http://www.yellowjersey.org Open every day since 1 April 1971

 

[Jobst Brandt]

Andrew Muzi writes:

>> Take that picture again (with the Presta stem) and use matte grey paper as a background. While
>> you're at it how about drawing some rectangular boundaries around the valve type groups. This is
>> a useful resource so it's worth doing. In fact the various items might even be labeled.

> An excellent suggestion.

http://www.yellowjersey.org/nuvalve.html

Oops! The valve stem in question is not readily visible in even the enlargement... but it has a
critical part missing, the contoured washer that goes between beveled hex nut and mushroom end to
capture the rubber of the tube. Meanwhile the extended Presta stem is one that separated from a tube
and is not interesting except for showing the separation. This would require a close-up.

Jobst Brandt [email protected] Palo Alto CA

 

[Bert]

On Fri, 18 Apr 2003 05:15:50 GMT, [email protected] wrote:

>Tim McNamara <[email protected]> writes:
>
>>>> Ho ho! That is not what the nut is supposed to do and creeping tires tear stems off easily."
>
>>> That is the purpose I always read in various publicated sources that mentioned them.
>
>>> What's your reason?
>
>> AFAIK, it's this. Schrader valves use either a screw-on pump head fitting or a
>> thumblever-compression head fitting, so you don't push much on the valve. Presta valves usually
>> use a press-on friction gasket pump head, so the stem retreats into the rim when you try to push
>> the pump head on. The jam nut is just a limiter for this.
>
>The reason people need to ask is that the manual frame fit (Silca Impero) pump of old is no longer
>used, nor are pumps in general. It's CO2 cartridges or mini pumps with hoses. Those who use pumps
>with integral pump heads, instead of pumping into their fist, often pump against the stem,
>breaking it off.

Real easy way here that I found to use a pump with integral pump head: lock the pump head on the
valve and simply hold on to the 2 spokes around the valve and pump into your fist/hand. This way you
can use quite a bit of force, all while stabilizing the bike and keeping the valve stem in place.

>This convinces them to use CO2 cartridges.

I use the pump on every fill. I would prefer to use a pump b/c I am not into purchasing air and
disposing of the wrappers for it. One of the reasons I cycle is to be environmentally friendly and
efficient.

Floor pumps with hoses or just pumps with hoses, as mentioned earlier, would also eliminate the
possibility of damaging the valve and surrounding area as well.

Bert

>
>Jobst Brandt [email protected] Palo Alto CA