Leaking presta valve stem extenders?

chriscross1966

Senior Member
Location
Swindon
Hi folks.... I've had a couple of mystery flat tyres on my Brompton recently. On neither occasion could I find any puncture in the tube. The common factor is that they both had the same valve core extender in them. The tubes are Schwalbe, as is the extender. The second one I caught before the tyre was fully flat and it seemed to respond OK to being pumped back up, and currently seems to be holding pressure OK. I did manage to get about an extra 1/8 of a turn on the extender/valve core by using the little widget that comes with the extenders.

Is this a common problem with the type of extender where you take the cores out of the stem on tube, put the extender in and then screw the core into the top of the stem (as opposed to the type where you leave the core in place with the inflation valve unscrewed and put the extender)? Is there a well understood and easily explained fix like plumbers PTFE tape or similar? Rubber solution the threads? Threadlocker?

I really am rather stuck with these extenders though, the rims are 40mm deep so the stock stems will not reach, and Schwalbe don't make a 60mm stem in that size tube, the tyres don't support tubeless (even if the rims did which I kind of doubt), the only 60mm stem tubes I've found in that size are pretty fragile and not exactly easy to get, whereas Schwalbe SV4's, whilst not the most common tube on the planet, are at least considered "normal" in any LBS that sells cargo bikes or recumbents.

thanks,

chrisc
 

MichaelW2

Veteran
 

Dogtrousers

Kilometre nibbler
I'm just curious about your wheels.

I know there's a world of Brompton whackiness out there, just wondering what they are.
 

Dogtrousers

Kilometre nibbler
Could you buy some long stem inners for bigger wheels, cut out the valve and surgically transplant it to your 16" tube of choice by means of rubber solution and fine sandpaper?

Actually a semi serious suggestion. If done with care it would be fully airtight, and you could say they were custom tubes (when in reality they are actually a hideous bodge).
 
OP
chriscross1966

chriscross1966

Senior Member
Location
Swindon
Could you buy some long stem inners for bigger wheels, cut out the valve and surgically transplant it to your 16" tube of choice by means of rubber solution and fine sandpaper?

Actually a semi serious suggestion. If done with care it would be fully airtight, and you could say they were custom tubes (when in reality they are actually a hideous bodge).
That sounds like a bit of a faff, and I'd like to point out the pink glowing elephant over there and to ignore the several days I spent getting an Ultratorque crank into a Brompton....
 
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