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What is the possible reason for a tube explosion

What is the possible reason for a tube explosion

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  #1  
Old 07-31-20, 03:40 PM
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What is the possible reason for a tube explosion

The rear tube of a bike had a very slow leak, so I decided to replace it with a new Schwalbe Road Bike 15 SV INNER TUBE 700 x 1 that I bought 2 years ago but has been in my backpack as a backup tube. I believe I seated the tube well. I heard an explosion when I inflated the tire. The enclosed picture shows the opening.

I have put back the old tube and everything looks fine now except for the very slow leak.

I am curious about the reason for the explosion. Was it caused by a defect of the tube? Is it a good idea to inflate a new tube to check it first before putting it in the tire?

I assume this new tube is not salvageable.


 
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Old 07-31-20, 07:46 PM
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I grew up in a family of six kids and spent a lot of time replacing tubes on bikes. Still do some now with relatives. It's always possible to pinch a tube with a screwdriver while putting the tire on. However that usually makes for a leak.... not a blowout. I've never had that problem.

I was reading the reviews on the brand of tube you used. Several mentions were made in regards to blowouts. One cause was believed to be old rubber and possible weak spot at a fold. Another cause was the tube did not fit in the tire correctly.
 
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Old 07-31-20, 08:17 PM
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Thank you for shedding some light on this.
I have just ordered two Kenda tubes because this post says they are durable. They are so inexpensive that I do not know if those on eBay are the same as those in the post. I went to Kenda's website and could not find any listing of bike tubes. I wish myself good luck!😀
 
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Old 08-01-20, 05:43 AM
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When I used to cycle I remember that tube choice was almost as important as the tire. It was a balance between durability and weight. When I wanted performance I would use a thin, light tube. For daily training or a road trip I'd pick a thicker, heavier and more durable tube. They even have compromise tubes that are thicker on the outside for durability and thinner on the inner part to keep the weight down.
 
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Old 08-01-20, 02:12 PM
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Too late now to know if tube was defective before inflating. One must be careful inflating tube by itself because when installed in a tire, the tire limits how much the tube can stretch. When you changed the tube, did you check for protruding spokes on the inside of the rim?
 
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Old 08-02-20, 08:36 PM
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I did not check, but I am quite sure it was not a problem because I did not have an issue at that spot. I have already ridden about 100K after putting back the old tube. Everything appears fine.
I found the slow leak is from the valve. I replaced its core with the one removed from the new blowout tube, the leak seems to have been reduced, but not eliminated.
 
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Old 08-03-20, 11:38 AM
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I've never so much as heard of a tube exploding while it remained properly confined within the tire. Explosions normally only will occur when the tube escapes confinement and can stretch to beyond what its modulus of elasticity will allow. And that is the nastiest, raggediest, most jagged failed tube I have ever have come across. And that one jagged tear going across the top of the tube runs out of sight, so this photo doesn't even capture all the damage.

My gut hunch is that such an uncommon failure probably had an unequally uncommon cause. If this happened when the bead was properly seated, and if the replacement tube hasn't yet suffered the same fate, I'm thinking either the tube had a manufacturing defect or suffered some damage that predisposed it to failure in the two years it spent in your backpack.

Have you examined the edges of the damaged petals closely, maybe with a hand lens, to see if there's any obvious variability in thickness? A substantially different in thickness might be evidence of a manufacturing defect. And if it were me I'd want to examine the inside of the failed area. In the interest of a more complete examination, I'd cut the tube in half with a scissors a few centimeters to either side of the failure, then cut that section open lengthwise on the side opposite the failure so I could examine the inside of the failed area.

Other details that might be important:

How did you inflate the tire? (floor pump, CO2 cartridge or can of high pressure air, etc)

Did your inflation source have a pressure gauge so you could monitor pressure as you were inflating? If so, what is the tire's pressure rating, what was your target pressure, and what was the highest pressure you noted?

Precisely when did the tube explode? (as it was being inflated, after and standing on its own, only after you put weight on it, etc)

How was the tube packaged when in your backpack? Was it still in the mfgr's box? Or other?

I ask this because my spare tubes generally only remain in my on-bike tool kit for from a few weeks to a few months before being pressed into service but I take great pains to prevent them being damaged in the meanwhile. My tiny little on-bike tool bag is way too small to accept the tube while still in a box so I unbox it, suck all the air out of it, close the (presta) stem tightly, fold it in a specific fashion that prevents the tube being damaged by its own stem, fasten it with a rubber band, dust it with talcum powder, and seal it inside a zip-lock sandwich bag (to prevent the talcum spreading throughout the tool bag). Then to insulate that from abrasion while jostling around inside the tool bag, it all goes inside a "woolen sack" that used to be the foot of an army sock.

Because a sucky day only gets suckier when you discover that the spare tube you were banking on to get you home won't hold air. It's an old habit left over from the days before cell phones but I still keep to it because cell service doesn't get everywhere, batteries can go dead without warning and, well, stuff happens. Its a best practice never to count on the cavalry coming to the rescue.

And BTW, a drop of fine lubricating oil in the valve stem might help with the slow leak.


EDIT:
BTW II, this was written by Jobst Brandt and posted on the website of late Sheldon Brown, the "dean" of all things cycling in the US, published before Sheldon's death so obviously with his approval:

Riders occasionally tell about a tube that blew out with a loud bang INSIDE their tire, leaving the tube with a long slash. The tube blew out, but not as described. If there was a bang, the tube was outside the tire. That is, the tire lifted off the rim and fell back in place after the tube burst.

Tubes do not burst inside tire casings, although they may leak, the most they can do is give off an audible hiss, assuming it is otherwise quiet enough. An un-socketed double walled rim can make a dull pop if the tube is exposed to the inner rim volume. The concept that a tube can explode inside a tire is dangerous, because it leads people to believe that tubes can mysteriously fail without apparent cause INSIDE a tire. With few exceptions, the cause is an improperly mounted tire.

Without understanding the cause, a rider may continue to risk a blowout, without realizing that tire lift-off can be caused by the tube's lying between the rim and the tire bead. In this position, the tube prevents the tire from seating properly in the hook of the rim, a condition that, under the right circumstances, will cause a blowout. This cannot occur inside the tire casing. To prevent blow-off, the tire seat must be inspected by pushing the tire away from the rim, upon which the tube should not exposed at any point around the tire.

Valve stem separation is another common failure, but it is less dangerous because it usually occurs while inflating the tire. If it occurs while riding it, causes a slow leak, as the vulcanized brass stem separates from the tube. When this occurs, the stem can be pulled out entirely to leave a small hole into which a valve stem from a latex tube of a tubular tire will fit. Stems from tubulars have a mushroom end, a clamp washer, and a locknut, that fit ideally. Such a used stem should be part of a tire patch kit.
 
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Last edited by Fred_C_Dobbs; 08-03-20 at 12:48 PM.
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Old 08-03-20, 07:04 PM
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Not sure what happened to this site. I could not log in until a moment ago.
Thank you for all the information.
I used a floor pump and the blowout with a bang happened when the pressure was 50-60 PSI. Everything looked fine. The tire did not have any abnormal signs. I actually tried to inflate the tire after the bang, but I could hear the hissing noise.
I put back the old tube after changing the valve core last Friday, rode about 100K the following day. The pressure still looks fine today (Monday), a little bit softer. I would ride without inflating it.

I cut the tube per your suggestion and took a photo of the blowout area. I do not see or feel any abnormality.

 
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Old 08-04-20, 11:15 AM
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Sorry Fred, didn't read your post. Apology if I'm repeating.

I see the blow out is near the valve. A common mistake is not pushing the valve up inside the tire allowing the tire to seat better into the rim. This step is always important but especially on a 1" tire.

IMO, not a defective tube.

Bud
 
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