Tube valve knut blown off!

yeachan153

Today, I unscrewed my valve cap to inflate tyres, and as i was doing so, the cap came off along with the knut, and the little thing you press down on to get air out of the pump. So now the tube stem stares at me with a gaping hole in the middle and no air. This isnt the first time its happenned; last time i screwed it back on and pumped it up, but found it to lose all pressure within a week, even as my back wheels remained pretty much the same. Could i claim for manufactures defect? Or is this something thats pretty common and my bad doing?

Aggieboy

yeachan153 wrote:

Today, I unscrewed my valve cap to inflate tyres, and as i was doing so, the cap came off along with the knut, and the little thing you press down on to get air out of the pump. So now the tube stem stares at me with a gaping hole in the middle and no air. This isnt the first time its happenned; last time i screwed it back on and pumped it up, but found it to lose all pressure within a week, even as my back wheels remained pretty much the same. Could i claim for manufactures defect? Or is this something thats pretty common and my bad doing?

You are screwing the little nut (valve tip) on the valve back up each time I presume?

yeachan153

The last time it came off, did just that before noticing it lost like 20psi everyday after that! I'm hoping lbs can give me a new one.. Surely it shouldnt blast off everytime i open the cap!

Dmak

Tube aren't expensive. Buy a 10 or 20 of another make. £2-4 each.

The specialized ones I got with the bike were crap. Both stems ruptured on inflation.

Quick Q to others reading, how many patches do you apply before you bin the tube?

dabber

It sounds like you had an inner tube with a removable/replaceable valve core and that this core was loose.

yeachan153

Dabber wrote:

It sounds like you had an inner tube with a removable/replaceable valve core and that this core was loose.

:shock: How would I go about tightening it? Hopefully it will stop the leaking air then!

dabber

With something like this I guess...... http://www.bikegoo.co.uk/product.php/386/weldtite_presta_valve_replacement_core_cap_kit

I've never done it myself.

dabber

Or perhaps one of these http://www.wiggle.co.uk/stans-no-tubes-core-remover-1/?utm_source=google&utm_medium=base&utm_campaign=products

andrewjoseph

I just used a pair of pliers over the flats of the valve core, if it has any. try using a pliers anyway. at worst you'll crush the thread of the dust cap.

sungod

pliers will do it, or one of the various valve core tools, the little plastic ones come with some valve extenders, an lbs may just give you a spare one

you need to do the valves up *tght*, you can do it on the wheel, but the best time is before you fit the tube

my experience is that the cores in new tubes nearly always need tightening

if you don't need removable cores, you can put a *small* dot of superglue/whatever on the core thread and then put the core in and tighten it, but imho this is overkill, if you tghten properly there's no need for this

Bobbinogs

Blimey, I am all for patching tubes, etc., but in this instance I would be tempted to just bin the tube and replace with another at £2.50. To make myself feel better about the profiligacy, I would cut out a small tubular section of the old tube and use it for C02 cannister wrap (to stop my little pinkies getting cold).

desweller

Those type of valve often come loose. I have a couple of Conti ones like that. There should be a couple of flats on there for you to get a spanner on them and tighten as much as you can.

yeachan153

Thanks for the responses. But i think my description was unclear; what has blown off is the little knut and the little screw which the knut slides up and down. The valve itself is still there, and the long metal cylinder (stem?) which sticks out of the tube is still there

neeb

yeachan153 wrote:

Thanks for the responses. But i think my description was unclear; what has blown off is the little knut and the little screw which the knut slides up and down. The valve itself is still there, and the long metal cylinder (stem?) which sticks out of the tube is still there

In some presta valves, the little nut and the little threaded shaft it screws up and down on are part of a "core" that can be removed from the outer part of the valve (the long metal cylinder, or valve stem):



In others, there is no separate core and the nut and threaded shaft are attached directly to the stem.

If the bit that has come out looks like the valve core above, you can screw it back in again and use narrow pliers to tighten it up. It needs to be tight otherwise it will come undone, especially if your pump has a screw-on attachment.

If it's just the nut and the threaded shaft that has come off, without a core that you can screw back in again, then I presume that the valve is broken - but then you said you had managed to screw it back in again before?

The advantage of the types of valves that have the removable core is that you can carry a spare core in your puncture repair kit, so if you ever manage to break the threaded shaft when pumping up the tyre on the road with a crappy mini-pump you can just replace the valve core.

sheffsimon

As others have said, I am all for patching tubes and preventing waste etc, but in this instance I would sling it.

Its nut, not knut by the way.

fludey

Or adopt my attitude....i never bother to fit the dust caps and can say i have not yet had any problems on my road or mountain bike with no dust caps in place.

On the question of patches....one at most but often end up binned after one flat. :oops:

yeachan153

@neeb: thanks for the clear-up! :oops: It is the core which has blown off, and i shall be tightening that with pliers; hopefully that will stop the air leaking!

@sheffsimon: yeaah, me too; but if a few pounds can be saved simply im all for it

@fludey: thats actually a really good idea; the core only flies off when i open the dustcap; feels alloy too so no rust Anyone else tried this?

neeb

The dustcaps are pretty much useless, throw them away!

Dmak

neeb wrote:

The dustcaps are pretty much useless, throw them away!

On the bike yeah, they seem pointless I agree. On a stashed tube however they can help stop the valve from damaging the tube.

Peddle Up!

Bobbinogs wrote:

Blimey, I am all for patching tubes, etc., but in this instance I would be tempted to just bin the tube and replace with another at £2.50. To make myself feel better about the profiligacy, I would cut out a small tubular section of the old tube and use it for C02 cannister wrap (to stop my little pinkies getting cold).

Or a willy cosy for the winter.