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Inner tube exploded. Why?

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Inner tube exploded. Why?

Old 05-14-13, 12:59 PM
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Torellian
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Inner tube exploded. Why?

I pumped up my rear tire and was careful not to overinflate it. In fact, I only pump up to around 50psi, even though the max is about 80. After about a minute after inflating it, it went BOOM. Now that I've had a chance to change the tube, I was surprised to find where the tube ruptured. The rupture was about a 6 inch long area on the rim-facing side of the tube.

I was expecting it might be on the sidewall-facing side, indicating the tube was not properly in the tire and was caught between the tire and rim. Or maybe the tire-facing side, indicating a sharp object embedded in the tire. I just replaced the rim tape a year ago with Velox. I checked it and it seems fine. So I replaced the blown inner tube with a new one, pumped it up, and all seems fine so far. Haven't ridden it yet.

Any ideas what could have caused the tube to explode like that? I've never seen (or heard) it happen before.
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Old 05-14-13, 01:07 PM
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fietsbob
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I'm Not looking over your shoulder to actually see where you Messed up.

Good luck, Is all I am saying.. .. be careful each time you re install the tire.

spoke ends covered , no tube left under any tire bead . Always Between Them.

expect the tube pushed the tire off the rim, and then you had the Blow Out.

Last edited by fietsbob; 05-14-13 at 01:15 PM.
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Old 05-14-13, 01:11 PM
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Originally Posted by fietsbob View Post

no tube left under any tire bead .
I suspect this.
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One morning you wake up, the girl is gone, the bikes are gone, all that's left behind is a pair of old tires and a tube of tubular glue, all squeezed out"

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Old 05-14-13, 01:21 PM
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I'm an amateur, but I know enough to say that a tube cannot go "boom" unless part of it has escaped the confines of the tire/rim. Most likely, part of the tube was caught between the tire and rim, and the partially unseated bead allowed the trapped tube to inflate, then explode. The only fix I know is to take extra care when mounting tires that the tube is completely inside the tire, then inflate to 20 psi or so, go around the tire on both sides popping the bead into the rim, then add more air and do it again, then fully inflate to desired pressure. That's the way I do it on a wheel/tire combo I have that has a loose fit (easy to mount by hand).

Last edited by Cross Creek; 05-14-13 at 01:23 PM. Reason: correction
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Old 05-14-13, 01:35 PM
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Originally Posted by Cross Creek View Post
I'm an amateur, but I know enough to say that a tube cannot go "boom" unless part of it has escaped the confines of the tire/rim. Most likely, part of the tube was caught between the tire and rim, and the partially unseated bead allowed the trapped tube to inflate, then explode. The only fix I know is to take extra care when mounting tires that the tube is completely inside the tire, then inflate to 20 psi or so, go around the tire on both sides popping the bead into the rim, then add more air and do it again, then fully inflate to desired pressure. That's the way I do it on a wheel/tire combo I have that has a loose fit (easy to mount by hand).
Thank you for your advice. I'm pretty much an amateur too. Not long ago, I used to have the LBS do my tube changes because I was afraid I'd do it wrong. After several tube changes and patches on my own, I think my fear has just been realized. A tube going BOOM unexpectedly in front of you tends to strike fear into a person!
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Old 05-14-13, 01:44 PM
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Blowing 'slimed' tubes is a bigger Mess. a neon green one.
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Old 05-14-13, 01:47 PM
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The amateur is exactly correct. If the tire is OK now then it was a portion of tube underneath the bead. The split can appear anywhere, as the tube is not necessarily in the tire with no twists, and may twist as it comes out of the tire. No need to be scared - just carefully push bead inward after mounting to make sure you can't see tire and rim strip is not sitting under the bead. Then inflate partially and check the bead line (some call it witness line) - the raised ridge of rubber running on the tire running just above the edge of the rim. It should be an equal distance from the rim all the way around on both sides. If up, deflate and look for a problem there. If it dives below the rim deflate, spray some mild household cleaner on the area (Fantastic, 409, etc) or use water wth a few drops of of dish soap mixed in, or talc (NOT both wet and dry!). then carefully inflate again, making sure there are not high spots. You will probably have to overinflate (as much as 100psi) and prepare yourself for a POP when the tire seats.
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Old 05-14-13, 02:13 PM
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What Cross Creek said. Also put a few pounds of air in the tube before mounting the tire on the rim. That helps keep the tube from getting caught under the bead to begin with.
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Old 05-14-13, 02:39 PM
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Then after you've mounted the tyre, pull it sideways so you can see down between the rim-edge and tyre. No tube should be showing. Then move over about 6" and pull the tyre sideways again and inspect the gap. Work your way all around the circumference of the tyre making sure no tube is visible. Then repeat for the other side of the rim/tyre.

Only once you've confirmed that no tube is caught between the tyre & rim, then you pump it up.
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Old 05-14-13, 08:25 PM
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It could have been just a bad seam in the tube. Also I always powder the inside of the tire to prevent the tube from sticking is some areas. After pumping up the tire a place where the tube might have stuck and then snapped loose could have caused your problem. I powder the tire, and after pumping the tire up after a patch or a new tube, I let most of the air out and then pump up again. That lets the tube seat itself properly.
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Old 05-14-13, 09:44 PM
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We have all experience the real problem in a variety of ways these days. Cheap materials/construction. Yes it may have had a good quality name on it but EVERYTHING we buy these days is engineered to meet legal requirements and not for longevity.

Many parts these days just fail for the hell of it.

The tube you replaced it with may last a month or many years, even with correct mounting every time.

-SP
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Old 05-14-13, 10:01 PM
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Originally Posted by speedy25 View Post
We have all experience the real problem in a variety of ways these days. Cheap materials/construction. Yes it may have had a good quality name on it but EVERYTHING we buy these days is engineered to meet legal requirements and not for longevity.

Many parts these days just fail for the hell of it.

The tube you replaced it with may last a month or many years, even with correct mounting every time.

-SP
Pretty much true, but will not by itself cause explosive failure; that DOES require space between bead and rim.

Originally Posted by rydabent View Post
It could have been just a bad seam in the tube. Also I always powder the inside of the tire to prevent the tube from sticking is some areas. After pumping up the tire a place where the tube might have stuck and then snapped loose could have caused your problem. I powder the tire, and after pumping the tire up after a patch or a new tube, I let most of the air out and then pump up again. That lets the tube seat itself properly.
Always possible.

Originally Posted by Cross Creek View Post
I'm an amateur, but I know enough to say that a tube cannot go "boom" unless part of it has escaped the confines of the tire/rim. Most likely, part of the tube was caught between the tire and rim, and the partially unseated bead allowed the trapped tube to inflate, then explode. The only fix I know is to take extra care when mounting tires that the tube is completely inside the tire, then inflate to 20 psi or so, go around the tire on both sides popping the bead into the rim, then add more air and do it again, then fully inflate to desired pressure. That's the way I do it on a wheel/tire combo I have that has a loose fit (easy to mount by hand).
THIS. Happens without warning, on just about any type of rim, with almost any type of tire. It happened to me THE ONE TIME I didn't have a perfect hook-up between my Michelin tire and Sun rim. Changed tires on those bad boys probably six times in two months over the last winter.
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Old 05-15-13, 01:54 AM
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Originally Posted by DX-MAN View Post
THIS. Happens without warning, on just about any type of rim, with almost any type of tire. It happened to me THE ONE TIME I didn't have a perfect hook-up between my Michelin tire and Sun rim. Changed tires on those bad boys probably six times in two months over the last winter.
EXACTLY! The tyre is a stiff, unyielding envelope surrounding the tube. IF the tube is fully encased inside the tyre, there is very little expansion of the tyre-casing within normal operating pressures. The tyre-casing simply cannot expand that much. Compared to pumping up just the bare-tube, just 5psi will have it expand 10x bigger than the tyre. IF some of that tube is allowed to squeeze out a gap anywhere so that it's not surrounded by tyre, then the +100psi pressure will cause the tube to expand 100x bigger than the tyre and ... >BOOM!!!!<

Typical commonly-accepted idea is that it takes double the pressure printed on the tyre's label to expand a properly-installed tyre's bead just slightly enough to push it over the rim. Then the tube is no longer contained inside the casing and >BOOM!!!!<
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Old 05-15-13, 02:17 AM
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Interesting set of replies I must concur that it was tube caught between the bead and rim.

I remember my father teaching me to repair a puncture. Our little lane had a hawthorn tree halfway along it, so punctures were a regular occurrence.

When reassembling the wheel, the following steps would be used:

Fit the tyre over the rim with one bead in the rim groove.
Install the inner tube into the tyre, starting with the value being inserted into the rim.
Pump in just enough air to make give the inner tube shape, but still be very soft (this was the critical bit to stop it getting caught between bead and rim).
Then work round the tyre bending the tyre over to pop the bead into the rim. (no tyre levers needed to refit the tyre, only to remove it)
Now work round the tyre bending the tyre over to check the inner tube is not visible between the bead and rim first one side, then the other.
Pump in a bit more air and then bounce the wheel working round the entire circumference to settle the tube.
Fully inflate.

Following this process and I have (to date) never had an inner tube failure or puncture repair failure.
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Old 05-15-13, 05:16 AM
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Originally Posted by rydabent View Post
It could have been just a bad seam in the tube.. After pumping up the tire a place where the tube might have stuck and then snapped loose could have caused your problem.
No, not true for an explosive flat. A seam letting go is extremely rare, except where the valve is glued onto the tube, and neither than nor any other problem that occurs entirely inside the confines of the tire/rim will cause a BANG! As already noted the tube must escape first (either under the bead or through a significant hole or tear in the tire).
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