bent presta stem

[Hell And High Water]

Seems I'm not smart enough to pump up a tire...


The little stem/rod on my tire valves keeps getting bent. I have a
decent Bontrager pump, but it has a nozzle that fits both presta and
schrader valves.

I can't seem to get it to seat correctly. When I first try to attach it
to the tire all the air rushes out, then I close it down, and it never
seems to be seated correctly. Sometimes no air is getting into the
tire, other times there's a delay, where the pressure goes way up, then
backs down to the correct amount.

Is this the bent stem? The two way pump nozzle or am I just dumb?


gracias


-Bob

[datakoll]

buy an adapter

[carlfogel@comcast.net]

On Sun, 2 Mar 2008 09:13:21 -0600, Hell And High Water
<bob.remove.helland@att.net> wrote:

>Seems I'm not smart enough to pump up a tire...
>
>The little stem/rod on my tire valves keeps getting bent. I have a
>decent Bontrager pump, but it has a nozzle that fits both presta and
>schrader valves.
>
>I can't seem to get it to seat correctly. When I first try to attach it
>to the tire all the air rushes out, then I close it down, and it never
>seems to be seated correctly. Sometimes no air is getting into the
>tire, other times there's a delay, where the pressure goes way up, then
>backs down to the correct amount.
>
>Is this the bent stem? The two way pump nozzle or am I just dumb?
>
>gracias
>
>-Bob

Dear Bob,

If the tube is already inflated, a presta valve that's been unscrewed
will stays shut until you pump enough pressure to force it open.

That causes the delay when the pressure goes way up while you pump.

For example, with a sticky presta O-ring you might see your pump gauge
rise to 100 psi with a few stokes and then abruptly drop to 90
psi--the tire had 90 psi, but it took an extra 10 psi to push the
presta valve open.

Schrader valves don't do this because a Schrader pump has a doohickey
that pushes the valve open against a tiny spring as soon as you put
the chuck on the valve--no air pressure is needed.

A dual-head bicycle pump pushes air through whichever hole has some
back pressure, using a clever little ball arrangement.

But if neither hole in a dual-head chuck has back pressure because one
hole is open and the other hole is connected to a limp inner tube,
then pure stinking luck decides which hole gets the air that you pump.

So the odds are 50-50 that air will whoosh uselessly out the open hole
on a dual-head pump if you attach it to an empty inner tube.

The trick is to push the inner tube against the base of the valve,
which creates enough back pressure to switch the pump where you want.

If you're inflating a bare tube, it's easy to push the inner tube
against the base of the valve with a finger. If you're inflating a
tire, just push a little harder on the same place on the tire.

If that doesn't clear things up, you could have a defective pump.

The solution would be to stop by the local bike shop and to ask them
to run through it with you.

They're human, so they like being asked if they're experts. (This is
the basis of RBT.) Even if the LBS doesn't sell you something, they'll
be just as pleased to have someone walk through the door as anyone
else in retail sales.

Cheers,

Carl Fogel

[Marcus Coles]

The conical valve of a presta stem gets wedged from the tire pressure.
Loosen off the little lock nut and give it a push with your finger to
unseat it prior to applying the pump chuck.

This will bring an end to the bending and save you from damaging the
pressure gauge with extreme pressure.

Marcus

[DanKMTB@gmail.com]

On Mar 2, 10:13 am, Hell And High Water <bob.remove.hell...@att.net>
wrote:
> Seems I'm not smart enough to pump up a tire...
>
> The little stem/rod on my tire valves keeps getting bent. I have a
> decent Bontrager pump, but it has a nozzle that fits both presta and
> schrader valves.
>
> I can't seem to get it to seat correctly. When I first try to attach it
> to the tire all the air rushes out, then I close it down, and it never
> seems to be seated correctly. Sometimes no air is getting into the
> tire, other times there's a delay, where the pressure goes way up, then
> backs down to the correct amount.
>
> Is this the bent stem? The two way pump nozzle or am I just dumb?
>
> gracias
>
> -Bob

In my experience those Presta/Schrader pumps are a PITA. I have one
as a backup, but almost never use it. I find it easiest to use an
adapter such as this one http://www.notubes.com/product_info.php/products_id/49
and a compressor for inflation at home, and CO2 when possible on the
road. If you don't have a compressor at home a decent floor pump is a
good option. The adapters can be had for $0.99-$1.99 US at any local
bike shop. I must have 5 of the things. Some live on the valves,
some live in saddle bags, and some are MIA - most likely lost in the
mess that is my shop.

[dustoyevsky@mac.com]

On Mar 2, 9:13*am, Hell And High Water <bob.remove.hell...@att.net>
wrote:
> Seems I'm not smart enough to pump up a tire...
>
> The little stem/rod on my tire valves keeps getting bent. *I have a
> decent Bontrager pump, but it has a nozzle that fits both presta and
> schrader valves.
>
> I can't seem to get it to seat correctly. *When I first try to attach it
> to the tire all the air rushes out, then I close it down, and it never
> seems to be seated correctly. *Sometimes no air is getting into the
> tire, other *times there's a delay, where the pressure goes way up, then
> backs down to the correct amount.
>
> Is this the bent stem? *The two way pump nozzle or am I just dumb?

(Is-it-plugged-in dept):
Are you using the correct chuck? Not familiar with the Bontrager, is
this a two-sided chuck, or do you swap parts out to convert between
presta and schrader?

Sounds like the schrader valve-opener pin (or, more correctly,
"doohickey"), part of the pump head or chuck, is hitting the presta
valve (?) or there is some other problem preventing the presta valve
doohickey from going into the chuck all the way (just to re-state the
obvious) which is causing both letting all the air out and poor
sealing. If you have a blow-up assembly photo, you might check to make
sure all is assembled as intended.

When adding air to a tire, unscrew the presta valve stem keeper all
the way (gently) and give that doohickey a little tap, carefully and
just enough to spit out a little air. Then the presta valve is unstuck
and you won't have to open it with air pressure. And you won't have to
pump nearly as much, either <g>.

IME, bending the presta valve's stem is a result of not anchoring the
pump head when using a "frame pump" (as opposed to a "floor pump"),
and not keeping the barrel of the frame pump steady while pumping.

Which model Bontrager pump are you using? --D-y

[Werehatrack]

On Sun, 2 Mar 2008 09:13:21 -0600, Hell And High Water
<bob.remove.helland@att.net> may have said:

>Seems I'm not smart enough to pump up a tire...
>
>
>The little stem/rod on my tire valves keeps getting bent. I have a
>decent Bontrager pump, but it has a nozzle that fits both presta and
>schrader valves.
>
>I can't seem to get it to seat correctly. When I first try to attach it
>to the tire all the air rushes out, then I close it down, and it never
>seems to be seated correctly. Sometimes no air is getting into the
>tire, other times there's a delay, where the pressure goes way up, then
>backs down to the correct amount.
>
>Is this the bent stem? The two way pump nozzle or am I just dumb?

A bent Presta will often fail to seal properly in my experience. To
keep from bending the stem in the first place, get a pump that has a
hose rather than one whose head is on the end of the pump's body.
Some people are able to pump a Presta with a hoseless pump and not
bend the stem, but I'm not confident that I'll be among them when I
need to be; I carry a Topeak Road Morph for that reason. (At home, I
can cheat; I have a compressor.)

--
My email address is antispammed; pull WEEDS if replying via e-mail.
Typoes are not a bug, they're a feature.
Words processed in a facility that contains nuts.

[datakoll]

buy 2

[datakoll]

know what a lock on pump head is? losescrews or bikepartsect sells it.
or Walmart sells an auto foot pump with a lock on head.
lock the head on, pumpumpumpump, no hand son head, pumpumpumpump, grab
the head lever, take a deep breath and scream eyyyahahayeyehahaha
lifting lever and head off.

works great. adds years to your lifespan.

[Hell And High Water]

In article <e51ms3pvib89uuc00e8trsrh2umk2s5f0i@4ax.com>,
carlfogel@comcast.net says...


> A dual-head bicycle pump pushes air through whichever hole has some
> back pressure, using a clever little ball arrangement.


This one only has one head, IE one 'hole' where the air comes out. Says
it works with both presta and schrader....

Good call on the LBS. That's actually where I bought it. I'll head
over there and ask them.


Thanks!

-Bob

[datakoll]

http://209.85.165.104/search?q=cache:9QXC7FVYIacJ:www.jerseyactionriders .org/BunnyHugs/presta_valve.htm+presta&hl=en&ct=clnk&cd=16&gl=us

http://www.google.com/search?q=presta+valve+inventor&rls=com.microsoft:*:IE-SearchBox&ie=UTF-8&oe=UTF-8&sourceid=ie7&rlz=1I7GGLJ

careful nut to loose de nut in de snow

[carlfogel@comcast.net]

On Mon, 3 Mar 2008 11:57:01 -0600, Hell And High Water
<bob.remove.helland@att.net> wrote:

>In article <e51ms3pvib89uuc00e8trsrh2umk2s5f0i@4ax.com>,
>carlfogel@comcast.net says...
>
>> A dual-head bicycle pump pushes air through whichever hole has some
>> back pressure, using a clever little ball arrangement.
>
>This one only has one head, IE one 'hole' where the air comes out. Says
>it works with both presta and schrader....
>
>Good call on the LBS. That's actually where I bought it. I'll head
>over there and ask them.
>
>Thanks!
>
>-Bob

Dear Bob,

Sorry, my mistake--I thought you meant a dual-head Schrader-presta.

You may have a single head with a reversible internal fitting.

If that's the case . . .

You have to unscrew the collar around the chuck, remove the internal
fittings, flip things around, re-insert them, and screw the collar
back on.

Here's a picture:
http://i32.tinypic.com/2n04mdc.jpg

Left to right:

A) collar
B) soft pressure fitting that clamps valve
C) reversible doohickey, presta one way, Schrader the other
d) pump body

Cheers,

Carl Fogel

[Hell And High Water]

In article <jiios39fsejnmi2fo56fthqfcqkv97cj5j@4ax.com>,
carlfogel@comcast.net says...
> On Mon, 3 Mar 2008 11:57:01 -0600, Hell And High Water
> <bob.remove.helland@att.net> wrote:
>
> >In article <e51ms3pvib89uuc00e8trsrh2umk2s5f0i@4ax.com>,
> >carlfogel@comcast.net says...
> >
> >> A dual-head bicycle pump pushes air through whichever hole has some
> >> back pressure, using a clever little ball arrangement.
> >
> >This one only has one head, IE one 'hole' where the air comes out. Says
> >it works with both presta and schrader....
> >
> >Good call on the LBS. That's actually where I bought it. I'll head
> >over there and ask them.
> >
> >Thanks!
> >
> >-Bob
>
> Dear Bob,
>
> Sorry, my mistake--I thought you meant a dual-head Schrader-presta.
>
> You may have a single head with a reversible internal fitting.

I think it's this one:

http://www.bontrager.com/model/05265/en

I don't think I'm supposed to change anything. It says:

Auto-select head instantly fits both Presta and Schrader valves




-Bob

[carlfogel@comcast.net]

On Mon, 3 Mar 2008 14:04:39 -0600, Hell And High Water
<bob.remove.helland@att.net> wrote:

>In article <jiios39fsejnmi2fo56fthqfcqkv97cj5j@4ax.com>,
>carlfogel@comcast.net says...
>> On Mon, 3 Mar 2008 11:57:01 -0600, Hell And High Water
>> <bob.remove.helland@att.net> wrote:
>>
>> >In article <e51ms3pvib89uuc00e8trsrh2umk2s5f0i@4ax.com>,
>> >carlfogel@comcast.net says...
>> >
>> >> A dual-head bicycle pump pushes air through whichever hole has some
>> >> back pressure, using a clever little ball arrangement.
>> >
>> >This one only has one head, IE one 'hole' where the air comes out. Says
>> >it works with both presta and schrader....
>> >
>> >Good call on the LBS. That's actually where I bought it. I'll head
>> >over there and ask them.
>> >
>> >Thanks!
>> >
>> >-Bob
>>
>> Dear Bob,
>>
>> Sorry, my mistake--I thought you meant a dual-head Schrader-presta.
>>
>> You may have a single head with a reversible internal fitting.
>
>I think it's this one:
>
>http://www.bontrager.com/model/05265/en
>
>I don't think I'm supposed to change anything. It says:
>
>Auto-select head instantly fits both Presta and Schrader valves
>
>-Bob

Dear Bob,

Sorry to keep misleading you--that is indeed an auto-select, no-fuss,
fits-either chuck design, so it may well be defective.

If your LBS still has the same model, they can take yours and compare
how they work on a tire. If it no longer works, then they might offer
to replace the fitting or even the whole pump. If neither model works
very well, then a new pump is the answer.

Cheers,

Carl Fogel

[Hell And High Water]

In article <dmmos395icjolkcg36jlp2sc2ftlnea26a@4ax.com>,
carlfogel@comcast.net says...
> On Mon, 3 Mar 2008 14:04:39 -0600, Hell And High Water
> <bob.remove.helland@att.net> wrote:
>
> >In article <jiios39fsejnmi2fo56fthqfcqkv97cj5j@4ax.com>,
> >carlfogel@comcast.net says...
> >> On Mon, 3 Mar 2008 11:57:01 -0600, Hell And High Water
> >> <bob.remove.helland@att.net> wrote:
> >>
> >> >In article <e51ms3pvib89uuc00e8trsrh2umk2s5f0i@4ax.com>,
> >> >carlfogel@comcast.net says...
> >> >
> >> >> A dual-head bicycle pump pushes air through whichever hole has some
> >> >> back pressure, using a clever little ball arrangement.
> >> >
> >> >This one only has one head, IE one 'hole' where the air comes out. Says
> >> >it works with both presta and schrader....
> >> >
> >> >Good call on the LBS. That's actually where I bought it. I'll head
> >> >over there and ask them.
> >> >
> >> >Thanks!
> >> >
> >> >-Bob
> >>
> >> Dear Bob,
> >>
> >> Sorry, my mistake--I thought you meant a dual-head Schrader-presta.
> >>
> >> You may have a single head with a reversible internal fitting.
> >
> >I think it's this one:
> >
> >http://www.bontrager.com/model/05265/en
> >
> >I don't think I'm supposed to change anything. It says:
> >
> >Auto-select head instantly fits both Presta and Schrader valves
> >
> >-Bob
>
> Dear Bob,
>
> Sorry to keep misleading you--that is indeed an auto-select, no-fuss,
> fits-either chuck design, so it may well be defective.
>
> If your LBS still has the same model, they can take yours and compare
> how they work on a tire. If it no longer works, then they might offer
> to replace the fitting or even the whole pump. If neither model works
> very well, then a new pump is the answer.
>


Thanks so much for your help!

-Bob

[jobst.brandt@stanfordalumni.org]

I believe that for pumps that use no hose, instructions on how to use
them, in bold print with an illustration, should be included. This
has been a problem with on-the-road pumps as long as I can recall.
Such pumps require that the user pump from one hand into the opposing
fist holding the pump head. For high pressure, holding the wheel with
grip over the tire is sure to bend (crack) the stem.

Presta valve stems are not designed to take lateral loads although
they will survive low pressure pumping. Do not pump against the stem,
but rather into the other fist that is holding the pump head onto the
valve stem.

Jobst Brandt

[datakoll]

thumblock heads from SKS or Parks listed as follows:

http://www.bicycletoolsetc.com/index.cgi?id=209635789680&nr=1&b=&c=Tools&sc=Tire-and-Tube&tc=Pump-Parts&q=&s=

http://www.parktool.com/products/detail.asp?cat=17&item=PFP%2D3

14. Silca Chuck for Presta/Schrader Brass/ Nylon
Item #SI-30: . $5.95 plus shipping More Info

Or the Silca chuck

Maybe the answer to the expletive deleted cheapo pump heads, if you
braze or pay for it. Welding or industrial supply probbably have
fittings matching say a Road Morp pump to a thumblock or silca chuck.

Clearly, a cheap pump head is imbecilic design, the thumblock the
answer. Maybe a Silca, no experience here but reviews are good.

[Werehatrack]

On Mon, 3 Mar 2008 19:27:53 -0800 (PST), datakoll <datakoll@yahoo.com>
may have said:

>thumblock heads from SKS or Parks listed as follows:
>
>http://www.bicycletoolsetc.com/index.cgi?id=209635789680&nr=1&b=&c=Tools&sc=Tire-and-Tube&tc=Pump-Parts&q=&s=
>
>http://www.parktool.com/products/detail.asp?cat=17&item=PFP%2D3
>
>14. Silca Chuck for Presta/Schrader Brass/ Nylon
> Item #SI-30: . $5.95 plus shipping More Info
>
>Or the Silca chuck
>
>Maybe the answer to the expletive deleted cheapo pump heads, if you
>braze or pay for it. Welding or industrial supply probbably have
>fittings matching say a Road Morp pump to a thumblock or silca chuck.
>
>Clearly, a cheap pump head is imbecilic design, the thumblock the
>answer. Maybe a Silca, no experience here but reviews are good.

A thumblock lever is not a guarantee of a good head. I've got a
Serfas pump that came with their version of thumblock lever head, and
to be blunt, it sucked. Or, rather, it blew...air out all the time.
I whacked the hose off and substituted a Zefal head, which solved the
chuck problem...at which point it became possible to get the pressure
up high enough that the pump's sealing failed at three other points,
including the tube/lower body joint and the hose elbow on the pump
base.

I scavenged the Zefal head back off, swapped it onto a cheapie
all-metal-body floor pump that I'd had around for 30 years (it was
Schrader-only, with the old-style "empty all of the air from a road
bike tube before you can get the hose end completely unscrewed"
connector) and stuck a T-fitting in the hose to connect a cheap
pressure guage. That worked.

Needless to say, I haven't bought any more Serfas pumps, though I have
nothing specific against any of their other products.

--
My email address is antispammed; pull WEEDS if replying via e-mail.
Typoes are not a bug, they're a feature.
Words processed in a facility that contains nuts.

[datakoll]

WHR-

problem is: where are the fittings found or how did you fit the pieces
together?
I found nothung small enough at Home Depot, haven't searched a more
complete stock of fittings.
The ususal run of gas hoses are too large for road pumps. I guess the
Parks is off gas line diameter, Parks sez larger diameter.
local noise is the SKS is no longer manufactured

I usually use Goop here but an untried glue is:
3M Scotch-Weld 3532 B/A Urethane Adhesive
$15/ 2 0z. tube kit (6 per case)
Available from
Hillas Packaging

[datakoll]

Cateye could try their hand at designing a pump.

[datakoll]

Pump tubing is in the refrigeration plumbing range?
if so, small to larger adapters are commercially available?