Puncture on valve stem - solution

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Redrhino
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Joined: 19 Aug 2018, 8:48pm

Puncture on valve stem - solution

Post by Redrhino »

Having pumped my Brompton tyre back up to 100psi, i returned later that day to find it completely flat.
I should have realised that the two events were probably linked.
There was a bit of a sharp burr on the valve hole in the rim and that had caused the stem to leak.

How to solve? Normal puncture patches only stick to the inner tube and you can't increase the thickness of the stem else it won't fit through the rim.

I was really peeved - with 5 destinations across London and no spare inner tube how could I avoid public transport?

Perhaps you would like to think before looking at my solution on the next post.
Redrhino
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Joined: 19 Aug 2018, 8:48pm

Re: Puncture on valve stem - solution

Post by Redrhino »

Brompton's have Schrader valves so no way to inject sealant so I nicked the inner tube and used a syringe to inject tubeless sealant.
Easy to do a normal puncture repair to cover the hole I had created.

After much hissing and spitting the valve stem healed. Hurrah! Off I pedal.
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mjr
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Re: Puncture on valve stem - solution

Post by mjr »

You can unscrew some Schrader cores but it needs a tool.

There are canisters of pressurised sealant which can insert it through the valve. Aldi sometimes sell them. Evans used to sell Zefal ones.
MJR, mostly pedalling 3-speed roadsters. KL+West Norfolk BUG incl social easy rides http://www.klwnbug.co.uk
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Brucey
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Re: Puncture on valve stem - solution

Post by Brucey »

mjr wrote:You can unscrew some Schrader cores but it needs a tool.


I think you can unscrew all schrader cores; that is an inherent part of the design.

cheers
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Redrhino
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Joined: 19 Aug 2018, 8:48pm

Re: Puncture on valve stem - solution

Post by Redrhino »

I think you mean Presta valves?

Schrader valves can’t be unscrewed I believe
Brucey
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Re: Puncture on valve stem - solution

Post by Brucey »

Redrhino wrote:
Schrader valves can’t be unscrewed I believe


No, as I said before they can all be unscrewed, that is the design.

Image

there are numerous patterns of valve core which are used in different applications (best not to use cores from bicycle inner tubes in your car tyres....) but they all share similar seal geometry and screw thread.

This is the extractor tool that unscrews them

Image

Some (metal) dustcaps have the correct fitting to work as a valve core extractor

Image

cheers
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NUKe
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Re: Puncture on valve stem - solution

Post by NUKe »

Redrhino wrote:I think you mean Presta valves?

Schrader valves can’t be unscrewed I believe

Some Presta valves can be unscrewed other cant.

but the Schrader ones just need the tool like this
https://www.eurocarparts.com/ecp/p/-/-/ ... atch%20All
NUKe
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Brucey
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Re: Puncture on valve stem - solution

Post by Brucey »

FWIW if you want to carry a single tool in your bike toolkit this one looks not bad;

Image

since it ostensibly will deal with both types of valve core as well as presta stem extensions.

cheers
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mattsccm
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Re: Puncture on valve stem - solution

Post by mattsccm »

Even the crappy plastic valve caps with slots in will take most Schraders out. I just used one of those metal caps jammed onto a bolt. Well about 5 of them actually.
The solution to the problem is to scuff the burr off with something hard and always carry a tube.
londonbikerider
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Joined: 22 Nov 2018, 7:58am

Re: Puncture on valve stem - solution

Post by londonbikerider »

This thread reminds me when a girlfriend had odd punctures on her Brompton. She then rpelace the front wheel with the new "double wall" rim and never had that problem again, so it may have been the hole for the valve causing problems? I remember seeing the rim tape of the old wheel, and it looked very narrow and not sufficient to protect the valve, but it may be only that wheel.
Brucey
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Re: Puncture on valve stem - solution

Post by Brucey »

FWIW I have done something similar to the OP when presented with a presta tube (with the non-replaceable valve type) which had the locking nut broken off the valve stem. I dismantled a similarly built valve from a ruined tube, and fitted the new valve inner part via a hole I made in the tube (which was patched afterwards).

Overall, it was a bit fiddly and probably not worth the effort if you can buy a new tube easily.

cheers
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Mike_Ayling
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Location: Melbourne Australia

Re: Puncture on valve stem - solution

Post by Mike_Ayling »

Redrhino wrote:Having pumped my Brompton tyre back up to 100psi, i returned later that day to find it completely flat.


Curious to know what width tyres you are running at 100psi?

Mike
londonbikerider
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Re: Puncture on valve stem - solution

Post by londonbikerider »

From what I've seen, Brompton branded tyres had a "100psi" mark on the side, and I think the Schwalbe Marathon run at that pressure, too
Brucey
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Re: Puncture on valve stem - solution

Post by Brucey »

the pressure rating on 16 x 1-3/8" marathons has been increased in recent years. The changes are summarised here

https://brilliantbikes.co.uk/brompton-tyres-tubes/165-schwalbe-brompton-marathon-tyre-35-349.html

and according to that you can run 110psi. I wouldn't do that on the older style Brompton single-wall rims though...

cheers
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reohn2
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Re: Puncture on valve stem - solution

Post by reohn2 »

If there's burrs on the inside of the rim best soften the edges with abrasive cloth @180grit or similar.
I always cut a 25mm square of old inner tube make a hole in the middle and push it to the base of the valve and similarly with any tubes I carry with me,it can be glued in place with rubber solution like a patch,though I don't bother myself
Last edited by reohn2 on 4 Aug 2019, 8:30am, edited 1 time in total.
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