Ghost puncture!

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Martian Tom
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Joined: 1 Aug 2022, 7:54pm

Ghost puncture!

Post by Martian Tom »

Here's one I've not had before...

I found my rear tyre flat today (road bike, 700 x 25c Schwalbe Lugano Endurance II tyre - new not long ago). Took it off and checked the tube thoroughly - not a puncture anywhere. Tyre likewise checked. The valve is okay, too. Put it back on, pumped it up - still rock hard 2 hours later.

Any ideas what might have caused that? The bike is kept indoors and no one else has access to it, so it's not sabotage! There is just one thing, though. I usually pump the tyre up to 80 psi. It has a range of 95 - 115 psi, but at 80 it's usually solid enough. However, I was reading a piece about ideal tyre pressures based on the cyclist's weight, and for me (12 stone 7 lbs) it recommended a minimum of 95 psi. So last weekend I pumped it up to 95 (bit of an effort getting there, too).

Could that have been a factor? I certainly can't think of anything else. :roll:
Jdsk
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Joined: 5 Mar 2019, 5:42pm

Re: Ghost puncture!

Post by Jdsk »

Did you observe it after pumping it up and before today?

Could it be a dodgy valve and it was left unsealed and leaky after you last inflated the tyre? But now it's sealing properly.

Jonathan
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andrew_s
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Location: Gloucestershire

Re: Ghost puncture!

Post by andrew_s »

No more than a possibilty, but it could be that when you pumped up from 80 to 95 psi, and before you put the pump on, you dabbed the valve to free it up, as you do, and the sudden rush of a bit of air out carried a bit of the talc that's often/usually inside the tube into the valve.
Then, when you'd finished pumping and closed the valve, a bit of the talc prevented the valve sealing fully, allowing it to go flat overnight.
Martian Tom
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Joined: 1 Aug 2022, 7:54pm

Re: Ghost puncture!

Post by Martian Tom »

Thanks, folks.

I eat my words! Flat again this morning. Seems the valve core was loose. I've changed the tube anyway, but I'll see if tightening the core works.

https://www.youtube.com/watch?v=C7XzK0p_03o
thirdcrank
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Joined: 9 Jan 2007, 2:44pm

Re: Ghost puncture!

Post by thirdcrank »

You can check for a leaking valve with an eggcup full of water. When you have inflated the tyre, and with the valve at the to of the wheel, dip the valve into the eggcup.
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Cugel
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Re: Ghost puncture!

Post by Cugel »

Martian Tom wrote: 11 Aug 2022, 9:14am Thanks, folks.

I eat my words! Flat again this morning. Seems the valve core was loose. I've changed the tube anyway, but I'll see if tightening the core works.

https://www.youtube.com/watch?v=C7XzK0p_03o
Those removable valve cores are handy for the tubeless - and I suppose if one goes perished i' the rubber bit, you can replace it - however .... They do annoy when your screw-on pump connection unscrews the valve core as you take the pump connector off after blowing up a tyre. Doubly annoying if this is out on the road post-puncture mending and it's taken you 140 pumps to get up to pressure with your weeny modern pump. (Ask me how I know this).

Two things help: lubricate the pump connector threads of any screw-on connector with a dry lube so it's less likely to lock too tightly to the valve core threads, risking the core being unscrewed with the pump connector; put on and take off the screw-on connector absolutely in-line with the valve, to avoid any sideways pressure between the connector and core threads dragging the core out.

Some of the teeny tools used to tighten valve cores aren't very effective at doing so. Those teeny plastic things that come with tubeless tyre valves are a case in point - they distort and fail to grip/turn the valve core flats when any significant torque is applied. A metal valve core screw/unscrew tool is better, something like these:
valve core tool.jpg
Cugel
“Practical men who believe themselves to be quite exempt from any intellectual influence are usually the slaves of some defunct economist”.
John Maynard Keynes
Barrowman
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Joined: 8 Jan 2022, 6:35pm

Re: Ghost puncture!

Post by Barrowman »

Do you have any sealant in the tube? My neighbor (who isn't very bike savvy) was complaining recently that his newly acquired (new) bike kept losing pressure in rear tyre ,he was having to inflate it daily. Investigation showed removable valve core with the tyre sealant gumming it up .
Galactic
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Joined: 21 May 2022, 7:42am

Re: Ghost puncture!

Post by Galactic »

+1 on checking the valve. Had this recently, drove me up the wall for a couple of weeks, didn't want to throw out a demonstrably sound (yet somehow still deflating) inner tube!

Putting the inner tube (including valve) under water showed nothing. But suspecting the valve, I held it under water for longer. Got one teeny bubble of air from the valve every 90 seconds or so which confirmed my suspicions.

In the end I used part of the chain tool from a multi-tool to loosen, brush clean and reinsert the valve core. Apart from talc or perished rubber another possibility is that the wee core (?) is bent.
rjb
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Location: Somerset (originally 60/70's Plymouth)

Re: Ghost puncture!

Post by rjb »

Galactic wrote: 11 Aug 2022, 12:32pm another possibility is that the wee core (?) is bent.
Often caused by removing the pump at an angle or levering it when trying to remove. :wink: keep it straight and thump the pump to remove it.
If you have an obviously bent core trying to straighten it can cause it to snap. :shock:
At the last count:- Peugeot 531 pro, Dawes Discovery Tandem, Dawes Kingpin X3, Raleigh 20 stowaway, 1965 Moulton deluxe, Falcon K2 MTB dropped bar tourer, Rudge Bi frame folder, Longstaff trike conversion on a Giant XTC 840 :D
Martian Tom
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Joined: 1 Aug 2022, 7:54pm

Re: Ghost puncture!

Post by Martian Tom »

Was definitely that loose valve core. It unscrewed and came out with no difficulty, just using my fingers. I tightened in back in with a pair of long-nosed pliers. Fine now. 8)
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Mick F
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Re: Ghost puncture!

Post by Mick F »

Schwalbe tubes with removable cores.
Bane of my life!

Trouble is, I have them on both bikes and I have four spares for each. If I ever need new tubes, they will NOT be Schwalbe.

What I've done to stop the things leaking, is to grip the valve stem with strong pliers and tighten the valve core to within an inch of its life. Seems to work.
Mick F. Cornwall
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Cugel
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Re: Ghost puncture!

Post by Cugel »

Mick F wrote: 13 Aug 2022, 10:53am Schwalbe tubes with removable cores.
Bane of my life!

Trouble is, I have them on both bikes and I have four spares for each. If I ever need new tubes, they will NOT be Schwalbe.

What I've done to stop the things leaking, is to grip the valve stem with strong pliers and tighten the valve core to within an inch of its life. Seems to work.
Bodging! The pliers are not the tool for tightening valve cores as they're likely to mince 'em. I mean! Would you knock a nail in with the battery end of your electric drill or stir the paint with your best flat blade screwdriver!? (Don't answer that). :-)

**********
I'm now reading that using a removable-core valve in an inner tube allows one to put in a glug of the latex stuff used with tubeless tyres, as the latex stuff can act within an inner tube as it does with a tubeless tyre - to bubble out a puncture-hole for a short while before turning to a solid and blocking the hole.

Has anyone done this successfully? (It's hard to know if it works as you never see it until you need to change the tyre/tube for some other reason, such as mangling the valve with some pliers, perhaps). I thought the latex stuff needed to exit to the air before it would go solid and block a hole?

Cugel
“Practical men who believe themselves to be quite exempt from any intellectual influence are usually the slaves of some defunct economist”.
John Maynard Keynes
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Mick F
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Re: Ghost puncture!

Post by Mick F »

I don't give a toss about spoiling the thread on the valve stem.
I don't use or need a clamp-screw, so there's nothing to unscrew.
Small BA spanner fits the core.
Dunno what size, as I cut the spanner so it's nice and short to fit between the spokes.
Mick F. Cornwall
offroader
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Joined: 18 Dec 2018, 4:47pm

Re: Ghost puncture!

Post by offroader »

I suffered this on a ride once and found a solution
It involved wedging the core into a crevice and twisting the tube to tighten it but for the life of me I can't remember what I used. Part of me thinks the narrow link in a 9 speed chain but in my mind's eye that's too big

It's worth remembering that any bike with a removable faceplate stem effectively has a small vice built in if you have a suitable Allen key
Ditto many seatpost saddle clamps
Chain tools can also be clamps if you're desperate enough. Come to think of it that might have been what I tightened the valve core with
I've used the stem vice a couple of times, necessity is the mother of all great bodges
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Cugel
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Re: Ghost puncture!

Post by Cugel »

offroader wrote: 14 Aug 2022, 12:45am I suffered this on a ride once and found a solution
It involved wedging the core into a crevice and twisting the tube to tighten it but for the life of me I can't remember what I used. Part of me thinks the narrow link in a 9 speed chain but in my mind's eye that's too big

It's worth remembering that any bike with a removable faceplate stem effectively has a small vice built in if you have a suitable Allen key
Ditto many seatpost saddle clamps
Chain tools can also be clamps if you're desperate enough. Come to think of it that might have been what I tightened the valve core with
I've used the stem vice a couple of times, necessity is the mother of all great bodges
One of these can be very useful indeed for tightening or slackening a number of things with wee flats on them:
spoke nipple tool.jpg
It has the advantage of being a "short spanner" which means that Mick won't have to hacksaw a proper spanner to get it in. It's also small and takes up hardly any room in the tool bottle. Mind, it weighs more than 5 grams so weight-obsessed fellows will probably prefer to walk home when their valve core goes loose than to carry such a speed-killer.

Many multi-tools also have small slots of various widths that will fit, amongst other things, valve core flats. However, they can be too long to easily get on to the flats so that they can be turned, as the spokes get in the way. Mick will be able to hacksaw such a tool, of course, but this may interfere with the other 28 tools on it. :-)

Cugel, always applying my tool in a proper fashion, for legitimate purposes, even a hacksaw.
“Practical men who believe themselves to be quite exempt from any intellectual influence are usually the slaves of some defunct economist”.
John Maynard Keynes
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