Unscrewing presta valve after pumping

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Mike777
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Joined: 29 Sep 2008, 9:11pm

Unscrewing presta valve after pumping

Postby Mike777 » 25 Oct 2010, 11:16am

Hi all

Had a problem on a long ride yesterday............

Had a puncture which was ok to fix, pumped up ok but when unscrewing the pump lead from the presta valve it actually unscrewed the top section of the valve and let all the air out.

Was able to screw the top section back but each time the same thing happened.

Has anyone had the same problem and any ideas on a fix ?

Thanks for your time

Mike

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jezer
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Location: North Wiltshire

Re: Unscrewing presta valve after pumping

Postby jezer » 25 Oct 2010, 11:21am

Yes, I've had that problem. Just tighten the valve very lightly with a pair of pliers. Should be ok.
Power to the pedals

manonbike
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Location: Sutton Coldfield

Re: Unscrewing presta valve after pumping

Postby manonbike » 25 Oct 2010, 1:37pm

Hum the very same thing happened to me with a presto valved tube after a punture, put a spare tube in pumped it up, as I released the pump from the valve the tyre deflated, the valve had disappeared some where off into the field I was in. I know how to remove scharder valves, but didn't know presto valves could come out as well. I'll have to give one of these presto valves the close eyeball to see how it comes a part? Yes I was left in the field, had to phone my nearest a dearest to collect me, I spose it was fair dooes as it the first puncture in about 2,000 miles.

Martyn.

ChrisButch
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Joined: 24 Feb 2009, 12:10pm

Re: Unscrewing presta valve after pumping

Postby ChrisButch » 25 Oct 2010, 8:55pm

Yes, as it happens I had this problem this very day! On some makes of tube the presta valve is itself an insert screwing into the valve body. You can easily loosen it unwittingly when unscrewing the dust cap - more often happens that way than when unscrewing the knurled valve seal to inflate. The trick is to press down on the dust cap as you unscrew it.

jawaka
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Re: Unscrewing presta valve after pumping

Postby jawaka » 6 Nov 2010, 2:31pm

I had a fortunately not injuring accident over a kerb which wrecked the inner tube and when I came to the first spare tube, the valve had dropped out. I used the second tube that I carry but didn't inflate it enough and got a snakebite puncture; I couldn't do an effective puncture repair on this, so I tried to take the valves out of the punctured tubes and put one in the unpunctured tube with the pliers of a leatherman, and when that didn't work I asked the man in a central heating van parked at the side of the road if I could use his pliers but that valve was obviously not the screwing out type. So I had two irrepairable tubes with good, but not unscrewing valves and one repairable tube with a screwing valve which had come out. Some kind cyclisits gave me a tube which was oversizied for my road tyres but eventually I managed to get it in and get myself home.
So no matter how well prepqared you are sometime you can still be caught out

gilesjuk
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Joined: 17 Mar 2008, 10:10pm

Re: Unscrewing presta valve after pumping

Postby gilesjuk » 6 Nov 2010, 5:27pm

Just use a pump which pushes onto the valve and then locks in place? (with a lever).

byegad
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Re: Unscrewing presta valve after pumping

Postby byegad » 8 Nov 2010, 9:05am

Sounds like a good recommendation for Schroeder.
"I thought of that while riding my bike." -Albert Einstein, on the Theory of Relativity

2007 ICE QNT
2008 Hase Kettwiesel AL27
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CJ
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Re: Unscrewing presta valve after pumping

Postby CJ » 8 Nov 2010, 12:10pm

Those unscrewable presta valves are useful if you want to put puncture-sealing gunk into your inner tubes. Plus you can salvage a valve (or two) out of any terminally punctured tube, to keep as a spare in case of valve failure.

The way to tell that your valve is a screw-in is that the dustcap threads are flattened in two places, so you can use a very small open-ended spanner on them. Another clue is that this part of the valve may be a different colour metal than the valve stem.

There is a snag that sometimes these valves are not screwed in tight enough at manufacture. I've had them unscrew when removing a valve cap, as already described by several people, and also recently had a tube that very slowly leaked from new - also solved by tightening it fully.

I find I can't reliably get thes valves tight enough with pliers, not unless they're locking pliers (it's one of the jobs I use my mini-Vise-Grips for). One brand of tube used to come with the valve core separate, in a bag together with a little plastic tool for tightening it. But I still prefer to use the Vise-Grips - after inflating the tube to maximum pressure, so the base of the valve is is securely anchored by friction against the rim and won't rotate when I tighten the core.
Chris Juden
One lady owner, never raced or jumped.

grognut
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Re: Unscrewing presta valve after pumping

Postby grognut » 8 Nov 2010, 12:24pm

Hi,

Had similar Sunday morning pumping up the tyres just before a trip out.
Unscrewed the cap and the valve came out.
I can't remember whose tube they were but they have a yellow cap, by memory it could be Specialized but I could be wrong.

I haven't checked it in detail but there didn't appear to be a very deep thread on the valve.

Cheers

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CJ
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Re: Unscrewing presta valve after pumping

Postby CJ » 9 Nov 2010, 10:19am

grognut wrote:Had similar Sunday morning pumping up the tyres just before a trip out.
Unscrewed the cap and the valve came out.
I can't remember whose tube they were but they have a yellow cap, by memory it could be Specialized but I could be wrong.

That'll be Continental I think. I hope you screwed it back in again and pumped up. The thing to do now is to give the valve core an extra firm tweak.

I've learnt that I have to tighten all uncrewable valves the first time I fit and inflate the tube, but provided I do that I don't have any trouble. If that didn't work I'd put a drop of blue Loctite on the threads.
Chris Juden
One lady owner, never raced or jumped.

grognut
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Joined: 18 May 2009, 12:05pm

Re: Unscrewing presta valve after pumping

Postby grognut » 9 Nov 2010, 12:25pm

Hi

Yes, I do remember buying some Continentals.

I did tweak it up firmly. I was contemplating putting a drop of screwlock on. I think I will now regardless.

I didn't realise they were unscrewable until this thread.

Cheers

nez
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Re: Unscrewing presta valve after pumping

Postby nez » 9 Nov 2010, 12:38pm

CJ wrote:. If that didn't work I'd put a drop of blue Loctite on the threads.
[/quote]

I don't suppose you'd like to tell the rest of us what you carry in the saddle bag by way of spares and tools, Chris? I'd never have thought of loctite but why not? It doesn't weigh much or take much space.

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CJ
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Re: Unscrewing presta valve after pumping

Postby CJ » 9 Nov 2010, 1:33pm

nez dans le guidon wrote:I don't suppose you'd like to tell the rest of us what you carry in the saddle bag by way of spares and tools, Chris? I'd never have thought of loctite but why not? It doesn't weigh much or take much space.

Nowadays I carry less and less :D . It depends on the circumstances, but I do sometimes carry a very small bottle of blue Loctite, and I have used it a few times "on the road". However I was suggesting the use of this at home, which is always the best place for maintenance.
Chris Juden
One lady owner, never raced or jumped.

MartinC
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Location: Bredon

Re: Unscrewing presta valve after pumping

Postby MartinC » 9 Nov 2010, 1:43pm

CJ wrote:at home, which is always the best place for maintenance.


Well, for scheduled maintenance yes. :D

Hank Scorpio
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Joined: 30 Aug 2018, 6:37pm

Re: Unscrewing presta valve after pumping

Postby Hank Scorpio » 30 Aug 2018, 6:45pm

Bit late to the party, but just bought a MTB and had the problem of my Presta valve completely unscrewing with my dust cap.. tyre went completely flat in 0.4 seconds! solution - screw the presta valve in nice and tight with fingers, no spanner. Then screw dust cap in lightly til it just bites. Problem solved!