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Old 04-16-17, 09:36 AM   #26
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Always a possibility. But in my opinion the dryness and apparent brittleness of the tube leads me to think it just let go.
It is a fallacy that rubber "dries out"...especially rubber that has been stored inside anything. Rubber that has been stored out in the open can become brittle because it is oxidized by ozone (mostly). But that process takes years of exposure and even the cardboard box that the tube comes in can protect the tube from ozone.

The other problem is that tubes can't just explode within the tire. There is no place for the tube to go and nothing to cause the tube to rip. In a properly mounted tire, the tube is expanded to completely fill the tire. Even if you are using very small tubes...say a 23mm tube...in a large tire...like a 37mm road tire...the tube isn't stretched far enough to tear if the tube is punctured from outside.
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Old 04-17-17, 07:02 AM   #27
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Swapped the winter tires for streets last Saturday. Rode 15 miles Sunday. Rode 9 miles to work yesterday. Rode 1/4 mile home last night and heard a weak pop as the front wheel went squirrley. The innertube had 3 or 4 patches leading me to believe it was two to three years old.

I always carry a spare tube and a pump. ten minutes later I was on my way.
D'Oh! I missed a couple of clues and a discussion elsewhere jogged the old memory file cabinet. You said you heard a "weak pop". Does the bike have rubber rim strips? If so, the tube could have moved the rim strip out of place and allowed the tube to expand into the double wall of the rim. This will result in a blow out without blowing the tire off the rim. The hole is usually much smaller and doesn't result in the kind of tearing in your picture but I suppose it could happen, especially if you happened to move the rim strip off of a couple of spoke holes or more.
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Old 04-17-17, 07:18 AM   #28
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D'Oh! I missed a couple of clues and a discussion elsewhere jogged the old memory file cabinet. You said you heard a "weak pop". Does the bike have rubber rim strips? If so, the tube could have moved the rim strip out of place and allowed the tube to expand into the double wall of the rim. This will result in a blow out without blowing the tire off the rim. The hole is usually much smaller and doesn't result in the kind of tearing in your picture but I suppose it could happen, especially if you happened to move the rim strip off of a couple of spoke holes or more.
Nah, sorry, man, but I don't buy it. The outer nipple hole in a double walled rim is not going to be more than 1 cm across. As you said, the rim strip may be shifted in installation, causing the tube to pop in one of the nipple holes; but when this happens, you get a star-shaped, or X-shaped, hole; not more than 1 cm long by any dimension. The OP's elongated tear happened when the bead came off the rim. There's just no other way. The weak "pop" was the bead coming off the rim; the bike felt wiggly because the wheel was no longer very round; and then it went "bang!"

I grant the possibility that the tube was very old. That is good. It is even possible that one or two of the patches in the tube contributed to the blowout because they interfered with the tire seating properly. But the tube's ultimate failure was caused by the tire/rim interface. There is no other way for this damage to occur.
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Old 04-17-17, 08:09 AM   #29
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The OP's elongated tear happened when the bead came off the rim. There's just no other way.
That would be my guess, and the bead may have popped back in once the tube was no longer pushing it out. I've had a few times the bead just wouldn't seat right, and several of those I wouldn't have noticed if not for the reflective sidewall ring that makes it a lot more obvious it's not evenly seated.
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Old 04-17-17, 08:40 AM   #30
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Nah, sorry, man, but I don't buy it. The outer nipple hole in a double walled rim is not going to be more than 1 cm across. As you said, the rim strip may be shifted in installation, causing the tube to pop in one of the nipple holes; but when this happens, you get a star-shaped, or X-shaped, hole; not more than 1 cm long by any dimension. The OP's elongated tear happened when the bead came off the rim. There's just no other way. The weak "pop" was the bead coming off the rim; the bike felt wiggly because the wheel was no longer very round; and then it went "bang!"

I grant the possibility that the tube was very old. That is good. It is even possible that one or two of the patches in the tube contributed to the blowout because they interfered with the tire seating properly. But the tube's ultimate failure was caused by the tire/rim interface. There is no other way for this damage to occur.

I agree that the elongated tear is more likely to result from a bead blowing off. I said as much above. BobbyG, however, said that didn't happen. A "weak pop" also isn't consistent with a blow off. They are loud even outside. And I agree that tubes that sneak through the spoke holes are smaller, star shaped holes.

However, a displaced rim tape over several holes could result in multiple tears which might propagate. It's a lot more likely than the tube being "brittle" and tearing inside the tire. That said, this mechanism is possible but not probable. I would agree that the blowout is more likely due to an improperly installed tire.
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Old 04-17-17, 08:47 AM   #31
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... A "weak pop" also isn't consistent with a blow off. They are loud even outside. ...
I see your point! But a "weak pop" is the sound of a bead coming off a rim; I have heard that. It is not the sound of the tube exploding, which usually happens a fraction of a second after the weak pop. My question for @BobbyG, then: did you only hear a weak pop, or was the weak pop followed by a blammo?

Edit: Eh, what do I know. Seems to me we are still missing a detail or two. I don't think we have the whole story. Which is not to say BobbyG is holding out on us; I'm not going to speculate further.
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Old 04-17-17, 09:43 AM   #32
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I don't understand all the attention this is getting, but it has been educational, entertaining and enlightening.

There was no "blammo". just a weak pop. As I had mentioned way earlier, it is possible the bead came off the rim, as I had mounted the tires a couple of days earlier, and had ridden about 25 miles before the flat.

I don't think it was a case of the rim tape shifting as it it still pretty secure on there, but that is a possibility.

I postulated it may have been an old inner tube letting go based on how the tube felt brittle and dry, but I am not a mechanical or forensic genius. It may have been was a poorly set bead, but I do check for the evenness of the mount and gradually hand pump the tire in three stages. First to 20psi, check the mount, then let out some air, then to 40ish, check and deflate to 20-ish, then inflation to the minimum as recommended on the tire, followed by an inspection, then to about 3/4ths of the recommended psi range. In this case 60psi where 65 is the recommended max and 50, the minimum.

In over 50 years of bicycling I have had loud blowouts and this was not one of them.
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Old 04-17-17, 02:17 PM   #33
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Old 04-17-17, 04:20 PM   #34
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Weak Pop is the name of my indie folk band
I loved their album, "Soda Flatts".
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Old 04-17-17, 04:29 PM   #35
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I had a tire blow out recently, which is very similar to a tire blowing off of a rim. It woke us all up, that's for sure. The tube in the OP must have had a weak spot to blow that way.

Since patch glue is only good for a short time after you open it, I save flatted tubes until I have quite a few and have a patching party. Back when I was running 30mm on tires on gravel, I had lots of flats. So I wouldn't have been happy paying for all those tubes.
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Old 04-17-17, 05:51 PM   #36
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Makes me wonder if my over-filing the tube before patching may have weakened that area of the tube.
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Old 04-18-17, 10:22 AM   #37
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I don't understand all the attention this is getting, but it has been educational, entertaining and enlightening.

There was no "blammo"....
Well, it gets my attention just because I'm puzzled and curious. I'm a strong advocate for patching tubes, rather than replacing, and tube failure is always interesting enough that it deserves explanation.

So, if your patience is not completely used up by now, another theory/question: any chance the tube was nominally too small for the tire? Say, a 25-32 mm tube in a 38 mm tire? That could have this result.
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Old 04-18-17, 11:28 AM   #38
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Well, it gets my attention just because I'm puzzled and curious. I'm a strong advocate for patching tubes, rather than replacing, and tube failure is always interesting enough that it deserves explanation.

So, if your patience is not completely used up by now, another theory/question: any chance the tube was nominally too small for the tire? Say, a 25-32 mm tube in a 38 mm tire? That could have this result.
No, I usually get at least 26x1.25, but not more than 26x1.5 as I find 26x1.75 innertubes too big to stuff in there.
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Old 04-18-17, 01:48 PM   #39
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My last blowout looked about like the op's except it happened while I was putting air in the tire. The rip started around the valvestem, and it looks like the stress from checking/adding air over the life of the tube weakened it enough to blow out.
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Old 04-19-17, 07:10 AM   #40
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Makes me wonder if my over-filing the tube before patching may have weakened that area of the tube.
Probably not. "Rubber"...actually styrene-butadiene polymer...used for tubes is highly elastic. You can inflate and deflate it many times without problems. Even if you over-inflate it and blow it up to several times its uninflected diameter, it will just spring back to the original shape.
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Old 04-19-17, 07:17 AM   #41
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Well, it gets my attention just because I'm puzzled and curious. I'm a strong advocate for patching tubes, rather than replacing, and tube failure is always interesting enough that it deserves explanation.

So, if your patience is not completely used up by now, another theory/question: any chance the tube was nominally too small for the tire? Say, a 25-32 mm tube in a 38 mm tire? That could have this result.
Still shouldn't have caused the kind of ripping that BobbyG saw. I regularly use 23mm tubes in 38mm tires. They take up less room as a spare. Going from 23mm to fill a 38mm volume is only an increase of 15mm which is only 3/4" of an inch larger than the nominal width of a 23mm tube.
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Old 04-19-17, 08:04 AM   #42
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^yeah, I know. I'm grasping at straws, here.

FWIW, I have seen a tear of this kind when using a 16" x 1" inner tube in a 16 x 2" tire. The small diameter of the wheel was presumably a factor. Apparently the tear started in the gap between two spoke nipples (even though there was a good rim strip in place) and tore to a couple inches long. Obviously this has to happen very quickly, before the air escapes.
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