Unscrewing presta valve after pumping

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fastpedaller
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Re: Unscrewing presta valve after pumping

Postby fastpedaller » 30 Aug 2018, 7:19pm

Hank Scorpio wrote: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!

A couple of large coins (2p) held one either side of insert and turned may just give enough leverage if a pair of pliers isn't in the toolkit!

Brucey
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Re: Unscrewing presta valve after pumping

Postby Brucey » 30 Aug 2018, 7:23pm

best to check all valve inserts are tight on all tubes when you buy them. If you carry a small adjustable spanner it is exactly the sort of thing that can be used to retighten valve inserts.

But this is the best idea IMHO;
gilesjuk wrote:Just use a pump which pushes onto the valve and then locks in place? (with a lever).


pumps that screw onto presta valves are (by and large) just stupid. My vote for 'best pump ever' goes to the zefal HPX
in black
Image
or classic silver
Image

also (since 2010, but not widely) available in a 'light' version (84g) which is a mini-pump with the same workings as the larger pumps (but shorter obviously)

Image

IIRC the HPX 1 is only 35cm long when compressed and (perhaps when strapped to be as short as possible) should fit easily into a saddlebag or pannier, so it is practically a mini-pump anyway. Does schrader or presta, and even makes a half-reasonable fist of doing woods valves too.

BTW the HPX design is now over 30 years old and there have been only very minor changes in that time; if it ain't broke, don't fix it....

cheers
-------------------------------------------------------------------------------
~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~

PH
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Re: Unscrewing presta valve after pumping

Postby PH » 30 Aug 2018, 8:42pm

Brucey wrote:best to check all valve inserts are tight on all tubes when you buy them. If you carry a small adjustable spanner it is exactly the sort of thing that can be used to retighten valve inserts.

I learnt, probably from here, that a chain tool is the exact size to tighten valve inserts. I don't know if the size is universal, all mine are the same size and at least three different brands.

Steve
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Re: Unscrewing presta valve after pumping

Postby Steve » 30 Aug 2018, 8:58pm

There is a special tool sold specifically for tightening the valve core, don't have one myself but have seen them online somewhere, possibly this forum....?

LollyKat
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Re: Unscrewing presta valve after pumping

Postby LollyKat » 30 Aug 2018, 9:13pm

Tufo valve key, made of plastic.
Image

I got one from Wiggle and keep it in my repair kit just in case, though have not needed it on my own bikes. Whenever I get a new tube I make sure the core is tight, and since getting an HPX1 pump which just pushes on I haven't had any problems.

MikeDee
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Re: Unscrewing presta valve after pumping

Postby MikeDee » 30 Aug 2018, 9:34pm

If you have a pump with a screw on head, don't use tubes with removable valve cores. There's not much point to them really, unless you want to inject sealant. There's only a handful of tube brands that use removable valve cores anyway.

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CJ
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Re: Unscrewing presta valve after pumping

Postby CJ » 21 Jan 2019, 7:21pm

Brucey wrote:pumps that screw onto presta valves are (by and large) just stupid. My vote for 'best pump ever' goes to the zefal HPX

I could say the same about pumps you have to hold both ends of. My vote goes to the Topeak Morph range of pumps: admittedly not as durable as a Zefal HPX, but far less effort - and some models come with a reasonably accurate gauge.
Chris Juden
One lady owner, never raced or jumped.

mr_mark_sid
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Joined: 8 Mar 2011, 4:13pm

Re: Unscrewing presta valve after pumping

Postby mr_mark_sid » 21 Jan 2019, 7:59pm

I use a spoke key for this job. I have one that has multiple sizes around its circumference so I can find a good fit for the valve with it. A spoke key is always good to have on the road so it is multi-purpose...

ged lawrenson
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Joined: 13 Sep 2013, 6:20pm

Re: Unscrewing presta valve after pumping

Postby ged lawrenson » 21 Jan 2019, 8:26pm


torrens
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Re: Unscrewing presta valve after pumping

Postby torrens » 23 Jan 2019, 2:56pm

I always use these little Knipex beauties for nipping up valve inserts:

https://1drv.ms/u/s!AhQ8LIQ_b7hJzVBVIsnGp4vwBdPO

Other sizes are available for bigger jobs (Bahco 4" adjustable also shown for reference)...:

https://1drv.ms/u/s!AhQ8LIQ_b7hJzVFkfVOal9Z13mg-

I've found these "wrench pliers" to have a number of advantages over traditional adjustable spanners:
1) Much quicker to set to jaw opening required.
2) Zero backlash so surfaces (esp. softish ones) aren't marred or rounded.
3) Almost self locking so the handle 'squeeze' force required is negligible no matter how much torque the user needs to apply (provided that they're used the right way round).
4) it's possible to use a pseudo ratcheting action by relaxing grip in order to do up fasteners etc requiring multiple rotations to close without ever removing the tool from the fastener.
5) the 125mm length version shown in the photos above has a jaw capacity of ca. 23mm which is more than that of even a Bahco 6" adjustable yet the Knipex pliers only weigh approx. 2/3 of the Bahco ones.

I've no connection to Knipex other than being an enthusiastic amateur user of some of their kit.

Marcus Aurelius
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Re: Unscrewing presta valve after pumping

Postby Marcus Aurelius » 23 Jan 2019, 3:07pm

This is not uncommon. The best option is to use single piece valves ( no unscrewable core ). However if you have valve extenders for super deep rims, or you want to use slime filling, to fix punctures, you need cored valves. To prevent them unscrewing, you just need to make sure that you only screw the inflator / pump on to the valve far enough to form a seal, not screw it on so far that you can’t turn it any further ( a mistake which is very common ). Then the pump / inflator should unscrew without taking the core out. Before you start the tube replacement, you can use a spoke key, or a dedicated valve core tool, to make sure the core is screwed in firmly enough.

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Mick F
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Re: Unscrewing presta valve after pumping

Postby Mick F » 23 Jan 2019, 3:15pm

I use a 7BA spanner and it fits fine.
Not perfect as it's a sloppy fit but there's only two flats so it's ok.

7BA is just over 4mm, so the 5mm Park Tool won't fit Shreader as it'll be too floppy.
Mick F. Cornwall

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Mick F
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Re: Unscrewing presta valve after pumping

Postby Mick F » 23 Jan 2019, 3:21pm

PS;
I use Lezyne pumps and they have screw-on heads and they are brilliant. Not stupid at all.
Mick F. Cornwall

PH
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Re: Unscrewing presta valve after pumping

Postby PH » 23 Jan 2019, 3:32pm

You might find that the flats on your chain tool are the right size for tightening your valves. I don't know if chain tools or valve sizes are universal, but my sample of two chain tools and two makes of tubes all work.
I think I picked that tip up from someone here, apologies for not crediting it, I am grateful :wink:

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Mick F
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Re: Unscrewing presta valve after pumping

Postby Mick F » 23 Jan 2019, 3:42pm

Just measured my Park Chain Brute chain tool and it does indeed fit Schreader valves at 4mm across the flats.
It's a chunky item to fit between the spokes though but it would be fine to tighten up the core with a bare inner tube before fitting.
Mick F. Cornwall