Presta valve core unscrewing with mini pump hose

Neil McC

Gaaargh! Had this happen on occasion but screwing it back in and trying again has done the trick.

However last night I got a puncture on the rear, no biggie, swap the tube with a previously repaired one and stick knackered tube in pocket to deal with at a later date. Inflate tyre with Lezyne mini pump, unscrew hose and the entire core comes out of the presta valve with the hose, whoooosh alll air exits the tube in a hurry. I must have pumped it up 7 or 8 times with the exact same thing happening so gave up with an acheing arm and walked the mile or so further home.

What's the best solution for this? Tighten the core so much with some small pliers that it cannot be undone by hand? Is the valve just knackered?

No probs at home as the hose on my track pump doesn't screw on to the valve, but that's no good obviously out on the road.

Continental race tubes.

woodywmb

Don't unscrew the pump hose end. It just pushes straight on and pulls off. The valve core will always loosen if it is turned anti-clockwise.

robrauy

Had this happen several times as well. I don't think all tubes have an unscrewable core, so reckon it's worth checking your tubes before you buy.

I still really rate my Lezyne mini pump though...

sungod

you just need to tighten the core

i use a lezyne pump that screws on, both bikes have tubes with removable cores, they never come undone, that's because they are tight

new tubes always seem to come with the core relatively loose, so always tighten before you fit a new tube (do the same for your spare if you carry one)

you can use pliers, but best is to get hold of the little plastic tool to tighten them, then you can keep it in saddle bag just in case - try lbs for one

probably weighs about 2g, looks like the one used in this picture...



if you're sure you'll never need to remove the core, you can put a dab of superglue on the thread then do it up, but tightening really should be enough

Monty Dog

A wrap of PTFE plumbers tape and re-tighten will hold it tight, or some medium grade Loctite e.g. hydraulic sealant. If you don't have the valve-core tool, a small adjustable spanner is fine to nip them up.

pdstsp

Great info here - I had exactly the same problem with exactly the same pump and with continental tubes a couple of weeks ago in -1 temperature. Thought it was just me being a pillock!! Have to say that it is a great pump apart from this. :oops:

Neil McC

Glad to see I'm not the only one who has come across this. Thanks for the replies everyone.

I'll keep and eye out for one of those tools.

meanredspider

I had exactly the same problem with my Lezyne frame pump. Stupid system - it's just conceptually wrong. Now use CO2 and have a micro pump for topping up or disasters. There's little more depressing than getting a flat in the pi55ing rain, fixing it, pumping the thing up only to have the air come whooshing out with the valve core....

sungod

meanredspider wrote:

I had exactly the same problem with my Lezyne frame pump. Stupid system - it's just conceptually wrong. Now use CO2 and have a micro pump for topping up or disasters. There's little more depressing than getting a flat in the pi55ing rain, fixing it, pumping the thing up only to have the air come whooshing out with the valve core....

in my experience there's nothing wrong with lezyne's system, it works fine, i have no problem with cores coming undone, and the hose greatly reduces the risk of bending/snapping a valve

if handlebars slip because the stem clamp is not tightened properly, it doesn't mean the stem clamp is conceptually wrong, it means it wasn't tightened properly

meanredspider

sungod wrote:

if handlebars slip because the stem clamp is not tightened properly, it doesn't mean the stem clamp is conceptually wrong, it means it wasn't tightened properly

That's correct but I was trying to think of another example of something in the engineering world where disconnecting something by unscrewing it works in the same direction as the item you're disconnecting it from (the conceptually "wrong" part of this system). Do you know of one? After all, you're relying on one just being tighter than the other - pretty crap in my opinion (but I'm only a fellow of the Institution of Mechanical Engineers so what would I know?).

The only decent example I could come up with is a stud fitting - undoing the nut tends to undo the stud - the BIG difference being that they are both disassembly - it's no big deal.

As for the hose point, again you're correct except that there's no reason that the hose has to have a screw fitting - my track pump has a hose but not a screw fitting.

If a screw fitting was such a good idea, inners would come with pre-tightened/sealed valves and all sorts of pumps would have scew hoses. The fact that they don't and Lezyne seem to be, in my experience, the only ones tends to indicate it's not such a great idea.

robrauy

FWIW I've just checked my used inner tube collection - The specialized tubes don't have an unscrewable core...

pottssteve

Neil McC wrote:

Glad to see I'm not the only one who has come across this. Thanks for the replies everyone.

I'll keep and eye out for one of those tools.

+1 for this also - had the same problem before, so now I know how to solve it.

Cheers,

Steve

ride_whenever

Removable cores are brilliant, but a pain if you find you're unscrewing them. The beauty of a screw on hose is that you can keep the pump lightweight without having issues of the connector blowing off, which can be an issue on track pumps once the rubber starts to perish or if you just pull it off rather than unlocking it first.

I have a spare core tool or two if anyone wants one, feel free to pm me.

Alumin-Liam

I've had the same problem in the past. Now I tighten with pliers and use a little drop of thread lock on all my tubes just to be sure. The first time I suffered this problem was probably the most annoyed I've ever been as a cyclist!

robrauy

ride_whenever wrote:

Removable cores are brilliant, but a pain if you find you're unscrewing them. The beauty of a screw on hose is that you can keep the pump lightweight without having issues of the connector blowing off, which can be an issue on track pumps once the rubber starts to perish or if you just pull it off rather than unlocking it first.

I have a spare core tool or two if anyone wants one, feel free to pm me.

Out of curiosity - what advantages are there to having a removable core ?

meanredspider

Alumin-Liam wrote:

The first time I suffered this problem was probably the most annoyed I've ever been as a cyclist!

+1 :!:

sungod

robrauy wrote:

Out of curiosity - what advantages are there to having a removable core ?

main thing is you can use decent valve extenders with deep rims - i got conti tubes in bulk on a deal too good to ignore, i reckon they'll last me the rest of my life, but i need extenders on the deeper rimmed wheels

you can replace the valve core if it gets damaged (with one from a torn tube), and if you're that way inclined you can inject sealant glop into the tube

philmerv

Yeah, had the same problem as many of you folks on here. I really had quite a frustrating time with it over the weekend. Never again though! I really don't see the logic in the design, it seems flawed. If I have deeper rims, I wouldn't fool around with all the extender gubbins. I'll just buy a tube with a longer valve. Simple.

I picked up a couple of new tubes at the local bike shop yesterday, with a solid single piece valve (specialized do them). Luxury. I explained the situation to the owner of the establishment and his reply was 'strange request'. I found the reply strange to be quite honest.

keef66

+ loads ^

Had to cut short a winter ride because of this; air was leaking past the valve core and I couldn't tighten it sufficiently with fingers I could no longer feel, nor any part of the multi-tool. Had to pump it up (with my Topeak Road Morph with it's clamp-on chuck) and sprint for home. Since then I've tightened all my cores with a tiny adjustable wrench and which I now keep in my bike tool-box.

This is probably a good job because since then I've also acquired a Lezyne mini pump with a screw-on hose .

trailflow

If the valve is unscrewing it means you are either 1. not checking your valves cores are tight enough to begin with or 2. you are screwing the Lezyne hose on way too tight. Which is not necessary.

If you find it still happens. Use a presta-to-schrader valve adapter (again not too tight) and switch the Lezyne hose around on the pump.

Also dont tighten the valves cores too much otherwise they could split the valve.

Another tip is put a dap of grease on the presta thread (or the hose thread) to stop the hose from sticking.

Nothing wrong with Lezyne pumps. It's operator error.

Moonbiker

I thought this was only a problem with conti innertubes, iv'e stoped buying them since it happened to me, switched to vittoria.

lettingthedaysgoby

This has just happened to me 5 times in a row.

My arms hurt from pumping and I'm cross.

This is all

ayjaycee

The very simple answer to the problem is to always tighten the valve core before first use. Pliers will do or Park make a dedicated (and cheap) tool for the job. I got into the habit of doing it to any new tubes as soon as I get them home and the little Park jobbie sits in my saddle wedge with the spare tubes just in case.

azzurri78

Moonbiker wrote:

I thought this was only a problem with conti innertubes, iv'e stoped buying them since it happened to me, switched to vittoria.

Same here. Happened to me with conti tubes so switched to specialized.

sungod

conti tubes ship with the valve fairly loose, if you tighten it then the pump head won't cause it to unscrew

meanredspider

sungod wrote:

conti tubes ship with the valve fairly loose, if you tighten it then the pump head won't cause it to unscrew

And here's the stupid bit. Why on Earth don't they assemble them properly? Sure, it's not difficult to pinch them up or carry yet another tool, but why should you? I also think that a screw on hose (a throwback to Dunlop valves) is stupid too. The combination is a perfect storm. To add to the issue, the hose popped out of the Lezyne pump I tried a few years ago. Fortunately it was on my commute and I managed to spot it on my return trip. I still have that pump somewhere at the back of a cupboard.

sungod

yep, it's annoying that they do it

tbh i gave up on lezyne screw-on heads as eventually the threads wear, i replaced with the slip chuck (fits the same hose as the screw-on head)

jgsi

It can be an issue with tubs.... but seriously .. if you have deeper section wheels . just get inner tubes that have non removable cores. The supply of tubes with differing lengths makes it EASY for the consumer to make the right choice.
I run tubs that for .. beyond me have non removable cores... but they are cheap to run on the commuter as tyre of choice...... but a pain in the backside to attach the extender.

e17blade

I had this happen years ago - but solved it by spraying a VERY SMALL amount of WD40 into the end of the hose. It doesn't effect pumping the tube up but stops it gripping too tight. Sorted.

ben@31

Ive had this before. Its caused by the dry valve sticking inside a screw thread pump with a high amount of friction.
All you simply need to do is put a drop of chain oil onto the valve core or if you're on the road with a puncture, rub your finger on the chain then around the valve core. This has always solved the problem straight away.