What's the deal with that Presta valve nut?

You know, the nut that screws on around the outside of the valve, and snugs up against the rim.

Is it necessary? Is there some benefit? Should it be tight? Should it be loose?

I've had several (expensive) tubes fail at the base of the valve core; the rubber seems to have worn
thin or been stretched thin. I'm wondering if this is due to making the presta nut too tight.

Thanks, Michael

 

[email protected] wrote:

> You know, the nut that screws on around the outside of the valve, and snugs up against the rim.
>
> Is it necessary?

No. I don't use them anymore.

> Is there some benefit?

It can make it slightly easier to start inflating a completely flat tube, if you have a pump
that doesn't lock onto the valve. I think the annoyance of having to screw and unscrew it is
greater, though.

--
Benjamin Lewis

Everybody is somebody else's weirdo. -- Dykstra

 

"Michael" <[email protected]> wrote in message
news:[email protected]...
> You know, the nut that screws on around the outside of the valve, and snugs up against the rim.
>
> Is it necessary? Is there some benefit? Should it be tight? Should it be loose?
>
> I've had several (expensive) tubes fail at the base of the valve core; the rubber seems to have
> worn thin or been stretched thin. I'm wondering if this is due to making the presta nut too tight.
>
> Thanks, Michael

I say leave it off. I use tubes which don't even have threads (torellis).

 

Michael Press writes:

> You know, the nut that screws on around the outside of the valve, and snugs up against the rim.

> Is it necessary? Is there some benefit? Should it be tight? Should it be loose?

It keeps the stem from wobbling around and sinking into the tire when pumping with a hand pump. That
is its only purpose.

> I've had several (expensive) tubes fail at the base of the valve core; the rubber seems to have
> worn thin or been stretched thin. I'm wondering if this is due to making the Presta nut too tight.

Unless you use more than your finger tips to screw it on, I don't believe this is the cause of your
stem separations. Some tubes are more susceptible to this than others. I have had a stem separate on
a wheel where I did not have a stem nut.

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.

Jobst Brandt [email protected] Palo Alto CA

 

The purpose of these nuts is to keep the valve stem perpendicular to the rim. Thereby preventing the
tube from tearing at that point.

As this is only likely to happen at low pressures, as when mounting the tire (or when you have a
flat and have not yet come to a stop), you can leave it off. Just be careful when you mount the tire
to be sure the valve stem does stay straight out from the rim. I don't have the nuts on my touring
bike tubes.

BUT, I _do_ have them on my mountain bike, for those trails which require me to ride them a lowered
pressures. like on sand, for example. In these situations, yes, the tube could creep and lead to the
aforementioned tearing.

May you have the wind at your back. And a really low gear for the hills! Chris

Chris'Z Corner "The Website for the Common Bicyclist": http://www.geocities.com/czcorner

 

On Mon, 14 Apr 2003 10:29:57 +0000, Michael wrote:

> You know, the nut that screws on around the outside of the valve, and snugs up against the rim.
>
> Is it necessary? Is there some benefit? Should it be tight? Should it be loose?

It should be tossed by the side of the road. To suggest that it serves a purpose in allowing you to
insert the valve in your pump suggests this would be impossbile otherwise. A finger pushing down
does just fine.

All the fuss people make about balancing wheels, and they hang these nuts on the heaviest part of
the rim&tire. Go figure...
>
> I've had several (expensive) tubes fail at the base of the valve core; the rubber seems to have
> worn thin or been stretched thin. I'm wondering if this is due to making the presta nut too tight.

Unless you really crank it down, probably not. Check the smoothness of your rim at the valve hole.
It might have a sharp edge that damages the tube.

--

David L. Johnson

__o | And what if you track down these men and kill them, what if you _`\(,_ | killed all of us?
From every corner of Europe, hundreds, (_)/ (_) | thousands would rise up to take our places.
Even Nazis can't kill that fast. -- Paul Henreid (Casablanca).

 

Chris Zacho wrote:

> BUT, I _do_ have them on my mountain bike, for those trails which require me to ride them a
> lowered pressures. like on sand, for example. In these situations, yes, the tube could creep and
> lead to the aforementioned tearing.

If your tube *did* creep, why do you think forcing the valve to remain stationary would prevent
problems with tearing?

--
Benjamin Lewis

On a paper submitted by a physicist colleague: "This isn't right. This isn't even wrong." --
Wolfgang Pauli

 

[email protected] writes:

> 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.

That works? What prevents the air from leaking out around the base of the inserted stem?

Joe Riel

 

One thing that can cause this type of failure is using a presta tube in a rim designed for a
Schrader valve. HTH

Ernie

Michael wrote:

> You know, the nut that screws on around the outside of the valve, and snugs up against the rim.
>
> Is it necessary? Is there some benefit? Should it be tight? Should it be loose?
>
> I've had several (expensive) tubes fail at the base of the valve core; the rubber seems to have
> worn thin or been stretched thin. I'm wondering if this is due to making the presta nut too tight.
>
> Thanks, Michael

 

Joe Riel writes:

>> 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.

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

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 tube that is about as large as the threaded stem diameter. A jam nut id then screwed down on
a slightly cup-shaped washer to capture the rubber against the mushroomed end of the stem, that
coincidentally has concentric grooves in it. The nut uses the same threads as the knurled nut that
started this discussion.

Do it. It works.

Jobst Brandt [email protected] Palo Alto CA

 

In article <[email protected]>, <[email protected]> wrote:
>Joe Riel writes:
>
>>> 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.
>
>> That works? What prevents the air from leaking out around the base of the inserted stem?
>
>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 tube that is about as large as the threaded stem diameter. A jam nut id then screwed down on
>a slightly cup-shaped washer to capture the rubber against the mushroomed end of the stem, that
>coincidentally has concentric grooves in it. The nut uses the same threads as the knurled nut that
>started this discussion.
>
>Do it. It works.

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.

--Paul

 

"David L. Johnson" <[email protected]> wrote in message
news:<[email protected]>...
> On Mon, 14 Apr 2003 10:29:57 +0000, Michael wrote:
>
> > You know, the nut that screws on around the outside of the valve, and snugs up against the rim.
> >
> > Is it necessary? Is there some benefit? Should it be tight? Should it be loose?
>
> It should be tossed by the side of the road.

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.

Andrew Bradley

 

[email protected] (Paul Southworth) wrote in message
news:<5PNma.34480$A%[email protected]>...
> In article <[email protected]>, <[email protected]> wrote:
> >Joe Riel writes:
> >
> >>> 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.
>
> >> That works? What prevents the air from leaking out around the base of the inserted stem?
> >
> >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

>
> 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.
>

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?

Karl.

 

Andrew Bradley <[email protected]> writes:

>>> You know, the nut that screws on around the outside of the valve, and snugs up against the rim.

>>> Is it necessary? Is there some benefit? Should it be tight? Should it be loose?

>> It should be tossed by the side of the road.

> 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 shit!!! 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.

Jobst Brandt [email protected] Palo Alto CA

 

Paul Southworth <[email protected]> writes:

>>>> 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.

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

>> 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 tube that is about as large as the threaded stem diameter. A jam nut id then screwed
>> down on a slightly cup-shaped washer to capture the rubber against the mushroomed end of the
>> stem, that coincidentally has concentric grooves in it. The nut uses the same threads as the
>> knurled nut that started this discussion.

>> Do it. It works.

> 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.

If you have a good bicycle shop nearby that caters to racers who insist on the lowest RR, they will
have old (flat) latex tubes. I have many of them left over from tubular days. I'm sure there are
dead tubulars around from which you can extract valve stems.

Jobst Brandt [email protected] Palo Alto CA

 

Karl Nelson writes:

> 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.

The real thing is a smooth and rounded mushroom end and looks much like what you seem to have
fabricated. The end is about the diameter of the knurled nut that started this discussion. I'm sure
you can make this air tight. By the way, this is where that little nut comes in handy, although the
real thing is a washer pressed against the tube by a hex nut that is strongly chamfered so that not
much of the wrench flats remain at the hex corners.

> Anyone have a picture?

I wrote to Sheldon to put one on the page with the various valve types that shows only the outer
ends protruding from a rim. It wouldn't be hard to include a picture of the whole stem.

Jobst Brandt [email protected] Palo Alto CA

 

Chris Zacho writes:

>> If your tube *did* creep, why do you think forcing the valve to remain stationary would prevent
>> problems with tearing?

> The purpose of the nut is to keep the tube from creeping in the first place. It's highly unlikely
> the tendency of the tube to creep is, by itself, going to be forceful enough to tear the tube. Put
> the valve in a vice and pull on the tube. see how much pull it takes to tear it, if you tear it.

Ho ho! That is not what the nut is supposed to do and creeping tires tear stems off easily. Dirt
motorcycles often use tire retainer bolts for running at low pressure to prevent just that. Creeping
tubes are not common on most bicycles but on fat MTB tires, run at low pressure for soft soil, it
occurs often.

> The tearing occurs when the valve gets cocked at a severe angle and get's ridden like this for
> long distance. Actually, it's almost as much a wearing as a tearing.

Oh bull shit. I have had stems separate that were perfectly straight. This is a manufacturing
problem and some tubes have it while others don't.

Jobst Brandt [email protected] Palo Alto CA

 

<[email protected]> wrote in message news:[email protected]...

> Oh bull shit. 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.

Matt O.

 

[email protected] 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.
>
> Oh shit!!! 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 and suggest the old memory is on the way out.

I've had/seen this happen _several_ times - not the memory, the nuts (the valve nuts that is).

I happily conceed that you are a fair bit older than me though.

Andrew Bradley

 

"David L. Johnson" <[email protected]> writes:

> All the fuss people make about balancing wheels, and they hang these nuts on the heaviest part of
> the rim&tire. Go figure...

You mean the lightest. With the wheel at rest, the valve is at 12:00, not 6:00. So adding the nut
will help balance the wheel .

Joe