Bit of a roadside disaster yesterday trying to assist someone with a soft rear tyre. Re-inflated with my trusty Lezyne mini-pump but upon unscrewing the pump – WOOSH! the valve core came with it…

I happened to be carrying a second pump which screwed on to the valve stem rather than the valve head, but it did exactly the same.

I am a fan of having a flex hose, but the only pump on the market which has a flex hose AND a thumb-lock head is the Topeak Mini-morph, which despite the name is pretty hefty for an emergency back up in your jersey pocket.

Is there anything else on the market?

New Lezynes have a purge in the valve head which (for me at least) hasn’t unscrewed any valve cores.  Hose is available separately:

https://www.wiggle.co.uk/lezyne-replacement-abs-hose/

Just get a small valve core tool, the real problem is most of them are only finger tight.

l.e. I don’t think the pressure is an issue, if it were you could simply unscrew the hose from the pump.

Hmm. Was going to say road morph. Maybe make sure the valve is tight before you fit the pump?… 😉

IME the Lezynes work fine as long as you’re careful. Valve cores should start off tight (but I find I can do them up plenty tight with fingers) and when you unscrew you just need to make sure the hose is straight and in line with the valve; it’s when you unscrew it with the hose bent that it rubs against the core and unscrews it. Residual pressure in the hose isn’t going to have any effect.

Since I’ve started taking care to keep the hose straight I’ve not had any issues.

My lezyne pump (I forget which one it is, it’s blue) does this if the valve cores aren’t done up properly.

Edit: +1 on keeping the hose straight.

Thanks folks, it doesn’t actually happen on my own bikes, either because I’ve tightened the valve cores myself or they are non-removeable.

It was just the farce last night trying to inflate someone else’s tyres which convinced me it wasn’t worth the risk of it happening on the roadside.

Someone on another forum pointed me towards the Syncros pumps which fit the bill perfectly, mini, flex hose, push on head.

https://www.syncros.com/gb/en/product/syncros-hp1-5-mini-pump?article=2505965515222

Silca Tattico. If your flush pay the extra and get the Bluetooth one and you will see what pressure you’ve got the tyre to.

My Giant one has been doing well for me for a couple of years now. Mini-MTB, I think it’s called.

I’d have to be feeling flush just to pay for the standard Tattico!

Got to admit I was tempted but it’s quite a big pump…

The Giant pumps look nice but are threaded connections.

From personal [bitter] experience carry a valve core tool and make sure the core is properly tight before attaching the pump just snug. Worked every time. I’ve been very sweary on a several occasions when not doing the above.

The gauge and seals on my lezyne eventually died and I’ve replaced with an SKS Spaero Double Action, not exactly petite or as nice in use but a better fit in my bag than the mini track pump if only because it hasn’t got sticky out bits.

Yeah it would make sense to carry the wee tool, but just seems like a better idea not to risk unscrewing the valve head in the first place!

Is there some disadvantage to the push on/thumb lock heads that I’m not getting? Someone else suggested they were harder to move the air through…

I understood Lezynes are notorious for the valve core unscrew behaviour.

Someone else suggested they were harder to move the air through…

I’d love to hear the thinking behind that 🙂

I love my Lezyne pump but it still unscrews the valve core.
I just remove the valve core and thread lock the cores of all my tubes. Especially the spare.
Only way to be sure.

my lezyne did the same all the time. binned it.
got a morphe road thing now. is ace.

Birzman pumps push down and lock, no unscrewing needed

Mine’s a Topeak Race Rocket. Flexi hose screw on job but I’ve never had it unscrew a core.

Attach a valve extender to the Lezyne hose. There’s enough space in the pump barrel to leave it on all the time and it doesn’t rattle. Cones in handy for friends with aero rims that forget one as well.

If you find yourself in this situation again, put a bit of oil from your chain on the outside of the valve, at least that’s what worked for me after several sweary attempts to avoid unscrewing the core at the side of the road.

Pump comparison

Residual pressure in the hose isn’t going to have any effect.

Actually, I think that’s exactly what causes the problem. Even if you only screw the hose onto the valve core very gently, you’ll find that once there’s pressure in it, a slightly loose valve core will always unscrew in preference to the hose. The pressure in the hose will place load on the threads, and I assume that some difference in thread pitch or size means that there’s then more friction in the hose/core threads than the core/valve threads.

Since switching the adapter on my pump to one with a pressure relief button, I’ve not had any problems. If you’ve got a loose valve core and do it up firmly with your fingers, and then put the hose on gently, you’ll find that you can get the hose back off again without trouble if you release the pressure first.

It’s an annoying trait of Lezyne pumps, but it’s solvable, and I definitely wouldn’t go back to minipumps without a hose.

If that ABS hose works, then as noted above, I should just try unscrewing the pump first and see if that helps.
I find it can happen even if I’ve tightened the valve core (to reasonable rather than extreme levels).

Have three Lezyne pumps, and had many more over the last ten years and this has only ever happened to me a handful of times and each time was because the core wasn’t tight.

Give the cores a nip with pliers or, even better, get one of the valve core removers. Pennies.

Even if you only screw the hose onto the valve core very gently…

I thought the hose screwed onto the stem? I shall have to check when I get home; five minutes of excitement and wonder await me in the garage, clearly.

I’ve “nipped up” the cores and the pump still manages to extract the damn things. I’ve tried removing pump from hose first but still the core gets pulled out.

It shouldn’t have to be solvable by customers, the pumps should be designed properly.

I eventually solved the problem by introducing the pump to the dustbin and buying a decent one.

Give the cores a nip with pliers or, even better, get one of the valve core removers. Pennies.

The little Park Tool valve tool is brilliant. I just nip the valve core up after gunking the tyre, problem sorted, they’re alloy so you can apply more pressure than with the little placcy ones. Bingo, no more Lezyne / valve core unscrews.

Generally I’d say the issue with press-on pump attachments is that they wear and then tend to pop off until you rebuild them, the Lezyne system is super secure ime.

Edit: there’s also a plastic press-on Lezyne attachment you can screw onto the standard adaptor so it’s then a press-on item if it really bothers you, erm…

https://www.wiggle.co.uk/lezyne-speed-chuck/

Not an answer to the actual question, but Milkit valve stems have a rubber thingy in the rim end that keeps air inside even though the core comes off.

With the Lezyne with the pressure relief you can unscrew the pump from the hose and leave the hose absolutely straight with no tension on it as you unscrew it from the core.

Works beautifully even on finger tight valve cores and you were going to unscrew the pump from the hose anyway.

This may be your answer. Not cheap. Absolutely brilliant pump IMO. This

With the Lezyne with the pressure relief you can unscrew the pump from the hose

Perhaps I’m being thick here but I’ve not quite worked out what the benefit of a pressure release valve is. I’ve never used the ones on my track pump or my mini pumps and I don’t seem to have any problems, let alone any which would be solved by letting it fart.

Lifeline motion floor mount mini pump £9 works brilliantly.

This may be your answer.

Max 50psi means it’s not much use for road/gravel tyres, though… (not sure what the OP is after)

my lezyne did the same all the time. binned it.
got a morphe road thing now. is ace.

+1

Valve cores should be left hand thread though. Stupid design.

Bodge to get you home. Pump up tire. Unscrew the hose from the pump and leave it on the valve, ziptied to a spoke

I second the LifeLine Motion Floor Mount Mini Pump…except it may be a little long to go in a jersey pocket!

Perhaps I’m being thick here but I’ve not quite worked out what the benefit of a pressure release valve is.

Honest answer Bez? I think it’s to allow you to unscrew the pump first – or at least that’s the only use I’ve found.

Apart from that I agree with you.

On a shock pump it’s different.

I used to have this problem with my Lezyne pump, so upgraded the hose. Now I tend to unscrew the hose from the pump first and then the hose from the valve, so there’s no pressure and easy to keep the hose in straight line.

Can you get any of the push on Lezyne quick chucks to fit the mini pumps?

I second the LifeLine Motion Floor Mount Mini Pump…except it may be a little long to go in a jersey pocket!

True, but it comes with a handy mount which can be used on bottlecage bosses or zip-tied to a tube of your choice.

On a shock pump it’s different.

Yeah, the one on my shock pump drops the pressure in the shock. Whereas the ones on my tyre pumps just take pressure out of the hose (including the one on my track pump, which has a chuck head, suggesting it’s nothing to do with unscrewing a hose… which surely you can do regardless of any residual pressure in the hose?). At least, as far as I recall that’s how they all work. I’ll be trying them all later. Rock and roll, huh.