Presta Valves

Graham Mason said:

This is going to make me look stupid but, I am new to Presta valves, & had a
slow leak on a wheel. I bought a pump that has a Presta adapter on it. I
unscrewed the cap on the valve, & when then undid the metal top part all
the air came out of the tube completely. I attached the pump, but could not
get air back in!

I am missing something?

Are you sure it was a Presta valve and not a Woods valve?

Sheldon, of course, has pictures:
<url:http://www.sheldonbrown.com/gloss_w.html>

I'm afraid I can't remember off the top of my head how Woods valves
work. My daughter's bike has them, but I'm not going to play with the
things unnecessarily! If you /have/ got Woods valves, and don't get a
more useful answer by tomorrow evening, then I'll have a look at them
and remind myself how they work.

--
Danny Colyer <URL:http://www.colyer.plus.com/danny/>
Subscribe to PlusNet <URL:http://www.colyer.plus.com/referral/>
"He who dares not offend cannot be honest." - Thomas Paine

Graham Mason said:

This is going to make me look stupid but, I am new to Presta valves,
& had a slow leak on a wheel. I bought a pump that has a Presta
adapter on it. I unscrewed the cap on the valve, & when then undid
the metal top part all the air came out of the tube completely. I
attached the pump, but could not get air back in!

Do you mean you unscrewed the little knurled nut and the air escaped
before you put the adapter or pump on? That shouldn't happen unless you
press the valve down.

Some (not many) Presta valves have removable valve cores that can be
unscrewed. Besides the cap, did you remove anything from the valve?

If the trouble started only after the adapter or pump was on, then
probably the adapter is rubbish or you're using the wrong adapter or wrong
pump head. You'd be better off using a pump that didn't need an adapter
anyway.

What pump and adapter? Can you post a link to a picture of one like it on
the net if you don't know model names.

~PB

I had had a look on Sheldon, & its definitely a Presta valve.

Thanks!

"Danny Colyer" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

Graham Mason said:

This is going to make me look stupid but, I am new to Presta valves, &
had a slow leak on a wheel. I bought a pump that has a Presta adapter on
it. I unscrewed the cap on the valve, & when then undid the metal top
part all the air came out of the tube completely. I attached the pump,
but could not get air back in!

I am missing something?

Are you sure it was a Presta valve and not a Woods valve?

Sheldon, of course, has pictures:
<url:http://www.sheldonbrown.com/gloss_w.html>

I'm afraid I can't remember off the top of my head how Woods valves work.
My daughter's bike has them, but I'm not going to play with the things
unnecessarily! If you /have/ got Woods valves, and don't get a more
useful answer by tomorrow evening, then I'll have a look at them and
remind myself how they work.

--
Danny Colyer <URL:http://www.colyer.plus.com/danny/>
Subscribe to PlusNet <URL:http://www.colyer.plus.com/referral/>
"He who dares not offend cannot be honest." - Thomas Paine

Graham Mason said:

This is going to make me look stupid but, I am new to Presta valves, & had a
slow leak on a wheel. I bought a pump that has a Presta adapter on it. I
unscrewed the cap on the valve, & when then undid the metal top part all
the air came out of the tube completely. I attached the pump, but could not
get air back in!

Did you remove something from the valve aside from the plastic dirt
cover (screw on usually)? If so, you removed the core of the valve and
need to restore it.

You unscrew a presta valve which allows it to take in or let off air.
You do not remove anything from the valve itself.

"Pete Biggs" <[email hidden]> wrote in
message news:[email hidden]...

Quoted message said:

Graham Mason said:

This is going to make me look stupid but, I am new to Presta valves,
& had a slow leak on a wheel. I bought a pump that has a Presta
adapter on it. I unscrewed the cap on the valve, & when then undid
the metal top part all the air came out of the tube completely. I
attached the pump, but could not get air back in!

Do you mean you unscrewed the little knurled nut and the air escaped
before you put the adapter or pump on? That shouldn't happen unless you
press the valve down.

Some (not many) Presta valves have removable valve cores that can be
unscrewed. Besides the cap, did you remove anything from the valve?

If the trouble started only after the adapter or pump was on, then
probably the adapter is rubbish or you're using the wrong adapter or wrong
pump head. You'd be better off using a pump that didn't need an adapter
anyway.

What pump and adapter? Can you post a link to a picture of one like it on
the net if you don't know model names.

~PB

I unscrewed the knurled nut, & the air escaped then before I put the pump
on.

I bought the pump from Halfords, as it was the only place open today!

Pic at link below:
http://www.halfords.com/webapp/wcs/stores/servlet/ProductDisplay?catalogId=10151&storeId=10001&productId=209487&categoryId=31576&langId=-1&parent_category_rn=31576&crumb=31270&varient=&CarSelectorCatalogId=&CarSelectorGroupId

Is there a rubber O ring or such under the knurled nut, do you know. I have
tried to get a cross sectional diagram of a Prest Valve.

Cheers
Graham

in message <[email hidden]>, Graham Mason

(') said:

This is going to make me look stupid but, I am new to Presta valves, &
had a
slow leak on a wheel. I bought a pump that has a Presta adapter on it.
I
unscrewed the cap on the valve, & when then undid the metal top part
all the air came out of the tube completely. I attached the pump, but
could not get air back in!

I am missing something?

Yes, although what it is I'm not sure.

Procedure:

Remove plastic dust cap. Unscrew lock barrel about one turn, just so it
isn't tight. No air should come out except when you press it. Attach
pump. Pump. Pump pump. Pump pump pump. Remove pump. Tighten lock barrel
until it is tight. Replace plastic dust cap.

Sorted.

--
[email hidden] (Simon Brooke) http://www.jasmine.org.uk/~simon/

For office use only. Please do not write or type below this line.

Simon Brooke said:

Procedure:

Remove plastic dust cap. Unscrew lock barrel about one turn, just so
it isn't tight. No air should come out except when you press it.
Attach pump. Pump. Pump pump. Pump pump pump. Remove pump. Tighten
lock barrel until it is tight. Replace plastic dust cap.

Sorted.

Not that it should normally matter if the lock barrel is unscrewed all the
way.

~PB

Graham Mason said:

I unscrewed the knurled nut, & the air escaped then before I put the
pump on.

This is a long shot, but touching the valve might have been the final
straw if the valve or tube was about to fail anyway. If I couldn't pump
it up, I would remove the inner tube and examine the bond between valve
and tube.

Quoted message said:

I bought the pump from Halfords, as it was the only place open today!

Pic at link below:

http://www.halfords.com/webapp/wcs/stores/servlet/ProductDisplay?catalogId
=10151&storeId=10001&productId=209487&categoryId=31576&langId=-1&parent_ca
tegory_rn=31576&crumb=31270&varient=&CarSelectorCatalogId=&CarSelectorGrou
pId

The pack implies that the pump is adaptable to Presta without needing a
separate adapter. I don't know that particular pump, but it looks like
the sort where there are pieces inside that are reversable. Get it the
way round that you think is suitable for Presta, unlock valve, push pump
onto valve, lift the pump's lever to lock it on.

Try Simon's method of just unscrewing the nut (or "barell"😉 just a minimal
amount.

Quoted message said:

Is there a rubber O ring or such under the knurled nut, do you know.
I have tried to get a cross sectional diagram of a Prest Valve.

No O ring there. No need as the pump should seal itself around the valve.

~PB

Take two:

Graham Mason said:

I unscrewed the knurled nut, & the air escaped then before I put the
pump on.

Could just be a sticky valve that caused that, but still it should be OK
to inflate. It may be just coincidence that you're also having trouble
pumping it up. Some pumps take a bit of getting used to, some simply
don't work very well at all.

~PB

in message <[email hidden]>, Graham Mason

(') said:

Is there a rubber O ring or such under the knurled nut, do you know.

No.

--
[email hidden] (Simon Brooke) http://www.jasmine.org.uk/~simon/

<p>Schroedinger's cat is <blink><strong>NOT</strong></blink> dead.</p>