Bicycle Mechanics - Cause of bursting tube?

I'm looking for a little insight into an odd thing that happened last weekend:

Saturday evening, we suddenly hear a loud popping noise from the room in which the bikes live. It turns out that the tube in the rear tire of my almost-new bike had suddenly burst. Upon examination, I can find nothing wrong with tire or rim. The tube is of course shredded.

I had the bike out for a ride of about 15 miles Saturday morning, but it had simply been sitting for at least 8 or 9 hours when the tube burst. Tires were aired up to recommended pressure (120 psi) before the morning ride. Bike had not been sitting in hot sun or under any other sort of extreme environmental conditions. Bike really is almost new; has probably about 150 total miles on it so far.

Took the tube, tire, and rim into LBS to see if they might see something I didn't. They also found nothing wrong with tire or rim, and had no idea why the tube might have burst.

What happened here? Was it just a bad tube? Is there another possible explanation? I've only been riding seriously for a couple of years, so I know there's a lot I haven't seen.

A bit of the tube was pinched between the tire and the rim. The tube finally found it's way to the outside and immediately blew out.

Or the tire was not properly mounted on the rim. If the hook on the tire is not fully seated below the hook on the inside of the rim the tire can blow off the rim. Usually it does this when first mounted but occasionally it can happened in a delayed fashion. Interesting to watch if you are there: it takes 2-3 seconds for the innertube to herniate out, inflate and blow, sounds like a 22 going off. Always a good idea to roll the wheel across the floor at least a full circumference while pushing down on the tire to seat the tire after mounting, before inflating. As you pump it up you will hear the tire popping into position.
Steve

Or the tire was not properly mounted on the rim. If the hook on the tire is not fully seated below the hook on the inside of the rim the tire can blow off the rim. Usually it does this when first mounted but occasionally it can happened in a delayed fashion. Interesting to watch if you are there: it takes 2-3 seconds for the innertube to herniate out, inflate and blow, sounds like a 22 going off. Always a good idea to roll the wheel across the floor at least a full circumference while pushing down on the tire to seat the tire after mounting, before inflating. As you pump it up you will hear the tire popping into position.
Steve

Better to inflate tire gradually and check seating as pressure is increased, especially with a tire that has a loose bead. Rolling a deflated wheel wont seat the bead, an inflating tube pushing bead onto hook on rim as it expands does.

Thanks for the explanations. I suspected that the tube must have somehow bulged out of the tire, but since I couldn't find anything wrong with the tire, I was confused. The tire not being properly seated on the rim would certainly account for what happened. Thanks.

Sure scares the the crap out of everyone present, doesn't it?!

I had the same thing happen when i mounted a new tire on my son's bike and didn't check that the tube was completely seated inside the tire bead. I pumped it up to 110 psi and we were just standing around a few minutes later when the tube exploded with a sound like a gun shot. My grandson, who was about 5 at the time, wouldn't go near the bike for weeks.

Sure scares the the crap out of everyone present, doesn't it?!

Yeah, no kidding. Sadly, my dog, who was already terrified of the bikes for no reason that we can determine, now runs in terror whenever he sees one. Poor traumatized critter.

I had the same thing happen when i mounted a new tire on my son's bike and didn't check that the tube was completely seated inside the tire bead. I pumped it up to 110 psi and we were just standing around a few minutes later when the tube exploded with a sound like a gun shot. My grandson, who was about 5 at the time, wouldn't go near the bike for weeks.


Grandson?! Geez, HR, you really are a Senior Member!

I'm going to have to treat you with a little more respect...

;)

Better to inflate tire gradually and check seating as pressure is increased, especially with a tire that has a loose bead. Rolling a deflated wheel wont seat the bead, an inflating tube pushing bead onto hook on rim as it expands does.

In my experience it does accomplish seating the bead, and I haven't had a lift off or bulge out since I started this practice. As I noted in the original comment if you are looking in the wrong place when the bead lifts off you have only a couple of seconds to react when the tube bulges out. This works best with a preshaped tire of course, if mounting a 220gm kevlar beaded tire, your method is the only one that would work. But after the tire rounds over from a few days on the rim I roll the wheel first.
Steve