Tubular, man

[ericmurphy]

...or is it "clinchular"?

I was out riding tonight, and noticed halfway through my ride that my front tire was way soft. Like, maybe 35 PSI, barely enough to protect the rim. I got home without having to do a roadside repair, and when I took the tube out of the tire (a Michelin AirStop butyl), I inflated it preparatory to locating the leak. I noticed a huge bulge about 20 degrees from the valve stem. I ran the tube through the bathtub, assuming the leak would be somewhere in the vicinity of the bulge. Nada.

I replaced the tube anyway, assuming there had to be a leak somewhere. But the new tube (same kind) had the same bulge! Is this something typical of this kind of tube? Did I end up with two defective tubes in a row? Or was there nothing wrong with the tube and I should stop worrying? That seems unlikely, since the front and rear tires were pumped up at the same time (a few days ago), and the rear was still around 100 PSI.

[froze]

If the bulge isn't leaking than it's not a problem; don't forget, when it's inside the tire that bulge will not occur due the tire restraining it.

When you did the leak test did you test the valve itself?

By the way, is the Airstop tube a self sealing tube?

[ericmurphy]

If the bulge isn't leaking than it's not a problem; don't forget, when it's inside the tire that bulge will not occur due the tire restraining it.

When you did the leak test did you test the valve itself?

By the way, is the Airstop tube a self sealing tube?

I know the bulge will be restrained by the tire, but I'm wondering if the reason the bulge is there is because the rubber is anomalously thin, hence leaky.

I tested the valve itself; no leaks there either.

I don't think the Airstop is self-sealing. It doesn't say anything about self-sealing on the box.

The tube's only got 400 miles on it, so I was sure it had a puncture somewhere, but if so, I couldn't locate it.

[Too Tall]

If you are pumping more than a few lbs of air into that tube (uninstalled) it will get fat but there should NOT be a bulge as you describe...that's a defective tube and yes I've see bad batches. I am not familiar with that tube but if it has a removable core...check them for tightness.

If you want reliably good and inexpensive tubes try plain old Performance brand...on sale about $3.

[davids]

I'm no expert, but...

That doesn't sound good. I think that a bulge/bubble in a tube can't be a good sign - The material must be thinner and weaker there. If it's sufficiently thin, I could imagine that it's permeable to air, and that could be your leak.

The thinness is also a weakness, and a blowout waiting to happen. :(