dabac

Hi all,
Even though I'm generally a patcher, and succesful and happy with that, I do sometimes treat myself to some new tubes.
This time, some Schwalbe Extralight.
One of those has been letting me down lately.
I came out, found the tire flat.
Took the tube out, pumped it up a little and found a 2 mm "pore" that had opened up on the rim side of the tube.
No sign of any pinching, rubbing or any of the other tiny signs one can see around a hole. Just a tiny, neat slit on otherwise pristine rubber.
Ran a finger round inside the rim. Felt OK.
And while the rim tape wouldn't have won any prizes, I didn't find any obvious reason for the flat.
Aiming to do it right the first time, I took the tire off, wrung it inside-out and gave that too a close look.
Nothing even mildly suspicious here.
Working off the vague indication of the status of the rim tape, I put another rim strip on, patched the tube, installed and inflated.
Two minutes later, there's a hiss and the tire goes flat again.
Pulled the thing apart, and there's another "pore" that has opened up, about 1" away from the 1st. Gave the rim another rub down and inspection. Gave the tire another inspection. Nothing.

Now, I know that actual material defects are comparably rare as a cause of flats, but here, it is beginning to look like the most likely cause.
(I had a bad batch of Geax tubes once which were prone to bursting unprovoked. Cutting them apart revealed a thin streak running along the tube, which was where they split open.)

What kind of defect would manifest like this anyhow?
The thin streak on the Geax batch was comparably obvious in comparison. The overstretched zone had lasting deformations in it. Cutting it open was simply verification.

So how many chances would you guys give a tube that flats for no obvious reason, one, two? Until you run out of patches?

TimothyH

I'm not a patcher so I can't answer your question but I will offer...

Rim tape or rim strip?

I've had very poor results with plastic rim strips. Repeated flats due to the strip's sharp edges.


-Tim-

Crankycrank

This ^^^ but if not the problem I'd give it about three tries. That's just me being the optimist trying to save a tube though. I use the Schwalbe Extra Lights as well, SV20 to be precise and am very happy with them. Never had an issue for a few years now. Of course it's not impossible to get a defective one and the way mfrs. move around to different countries to produce their products quality control is never guaranteed. The last time I bought these less than a year ago they were being made in Indonesia and are top quality. First I would try another tube to see if you get the same problem and go from there.

San Rensho 

Its probably not the tube, its the tire. Theres something very small stuck in there that is causing the flats.

freeranger

Take a dryer sheet and drag it around the rim and around the inside of the tire. Dryer sheets are great for snagging and showing up any burrs.

masi61

I put 26 x 1.25” Schraeder valve Schwalbe tubes on my girlfriend’s Hard Rock mountain bike to make it road worthy.

One tube was fine, the other would go flat pretty quickly with no apparent source. The removable valve was tight and the submerged tube did not show any bubbles.

I ultimately replaced the tube and while that one did not have any apparent slow leaks, as bad luck would have it, it succumbed to punctures from little bits of wire staples on 2 different occasions.

I do wonder a bit about Schwalbe tube’s quality control. I thought I read somewhere (maybe on their website) that they individually test every tube, but I’m not so sure I trust that.

Retro Grouch 

My bet is it's the rim strip. If you are using those plastic things rather than rim tape, I'd double my bet.

It only takes the tiniest little arc of unprotected spoke hole. Ultralight inner tubes, I assume, would require even less exposure. When you pump your tire up to operating pressure, the air pressure tries to press the inner tube against that raw metal edge.

Unca_Sam

I give up on patching when the valve stem develops a cut!

I know these special rubber bladders aren't invincible, but I haven't had a large enough pinch flat or blowout that's too large for a cement patch.

Gresp15C

Inevitably, despite my best efforts, I screw up the tube, most often stem failures on Presta tubes. Those can't be repaired.

dabac

The rim came with rim tape, the glossy, plastic kind. It had sunk farther into the nipple cutouts than I like to see, which is why I was suspicious of it.
I fitted a rim strip since it was faster, one that came off a wheel that hadn't had any problems.

And while I can see a sharp edge on a rim strip causing issues eventually, one puncturing a tube while the bike is parked does seem extreme.

Wilfred Laurier

Any failure or leak at the base of the valve stem, or inside the valve, makes replacement necessary. Rough handling when pumping (esp. removal of a too-tight presta valve chuck) is the usual cause of this type of failure.

Any other leak can be patched.

'Mysterious' or repeated leaks are almost always caused by a problem with a component other than the tube - rim tape, tire, rim, spoke, etc., and replacing the tube without finding and fixing the root cause will just result in the new tube getting damaged. If I am getting repeated flats and find a previously unnoticed tiny thorn or piece of wire in the tire was causing it, removal of the cause and a patch on the damaged tube is sufficient.

dabac

Update:

After the front developed a leak too, seemingly while being parked, I ditched the tubes in favor of some from my patched stock. For now at least the issue has been resolved. No more pores opening up after inflation.

venturi95

i concur with RetrGrouch in post #7 . Changing out tubes does not fix the source of your consternation.