[Orb]

Was doing some laundry after today's road ride, and I hear a *BANG!* from inside the garage. Run out there, thinking somebody broke in or whatever, and see nothing unusual. Noticed that I hadn't hung the bike up on the rack, so I do that, and notice the front tire looks a little funny. Not funny like a clown, funny like "holy ****, I'm glad that didn't happen during a 40MPH downhill".

The tube apparently had failed catastrophically, blowing the sidewall of the tire right off the rim. I pulled the tube out to find that there is a 2" tear in the side. Brand new tube, had maybe 80 miles on it at 110-120psi.

Guess I won't be repairing that one. This isn't "normal" road tube failure, is it? I'd hate for that to happen on a fast DH.

 

[JayTee]

Sounds like it was pinched under the bead to me. Why it blew exactly when it did is a mystery, but I can't think of another explanation for what you described.

I mean, you didn't just have a tube fail, it also blew your tire off the rim?

 

[wim]

Cause and effect reversal.

It's highly unlikely that air escaping from a tube will unseat a properly mounted tire.

As jtolleson said, the usual cause of these stationary bike blowouts is a tube that's gotten pinched under the tire bead during a hurried mounting job. Ever so slowly, the air pressure inside the still intact tube works the tire away from the rim at the pinch until it has created a small opening between the tire and the rim. This can take hours. At the moment that small opening has grown large enough, the tube in one instant forces itself out of the opening, forms a bubble and then blows itself up (think popping bubble gum). Time is one of the determining factors - that's why these blowouts often happen in the dead of the night on a stationary bike.

 

[Orb]

Sounds like it was pinched under the bead to me. Why it blew exactly when it did is a mystery, but I can't think of another explanation for what you described.

I mean, you didn't just have a tube fail, it also blew your tire off the rim?

Yup, it blew about 8" of tire right off of the rim. Couldn't have done a better job if I used a tire lever.

Hard to believe I pinched the tube in there...the tire has been mounted for two weeks or so and has seen some miles at 120psi. Every time I install a new tube, I put a little pressure in at a time and work around the perimeter of the tire with my hands to make sure everything's copacetic. I guess anything's possible, though.

 

[wim]

See-saw.

Hard to believe I pinched the tube in there...the tire has been mounted for two weeks or so and has seen some miles at 120psi

Sometimes the pinch is very small and unseats a tire very slowly. Riding the bike will push the tire back in place to some degree. Parking the bike will start the unseating process again. At one point, the unseating prevails and allows the tube to escape and burst.

A tube cannot explode inside a properly seated tire. If a tube rips for some reason inside a properly mounted tire, you would just get an instant flat.

 

[A4B45200]

Yup, it blew about 8" of tire right off of the rim. Couldn't have done a better job if I used a tire lever.

Hard to believe I pinched the tube in there...the tire has been mounted for two weeks or so and has seen some miles at 120psi. Every time I install a new tube, I put a little pressure in at a time and work around the perimeter of the tire with my hands to make sure everything's copacetic. I guess anything's possible, though.

Any chance you used CO2 to fill the tube? This happened to me once. I flatted on the road, changed tube and filled with CO2 to get home. Next day, I checked pressure as I usually do before my ride and saw it was a bit low (maybe 85psi). I pumped it to 115 psi and got ready for my ride.

On my way to get my bottles, I hear that loud 'bang'. The tube burst and the sidewall of the tire was off the rim as well. Not sure if mixing CO2 and regular pump air (excuse the ignorance) caused this. But it could have also been improper tube installation on the road the day before. Since then, if I filled with CO2 on the road, I deflate it completely once I'm home...then re-pump. Never had the issue again.

 

[Kerry Irons]

Misunderstanding cause and effect

Not sure if mixing CO2 and regular pump air (excuse the ignorance) caused this. But it could have also been improper tube installation on the road the day before.

Well, I'm sure about two things: mixing CO2 and air DID NOT cause this, and improper installation most likely did

 

[A4B45200]

Well, I'm sure about two things: mixing CO2 and air DID NOT cause this, and improper installation most likely did

Hence my ignorance But hey, at least I know better now!

 

[fisherman]

I agree. It was probably a case of improper installation.

I was once pumping air into my wife's commuter bike when that happened, and it was right in front of me too. The loud BANG was indeed extremely impressive. Left my ears ringing, and bent the crappy rim that was in it too! The force was pretty bloody impressive.

From then on, on new tube installations especially, I would pump up to around 30-40 psi, release air, pump more, release air, pump .... I will also visually check and "massage" the tyre to try and make sure it is seated properly. Then, when at correct pressure, I will leave it and come back the next day to release more air, and pump it again fully. Anal? I guess, but when you have a tyre going BANG, you really would not want it to happen again.

Don't laugh! ;-)

Btw, on already seated tubes and tyres, I do not do it of course. Just a straight on pump.

 

[tanhalt]

Any chance you used CO2 to fill the tube? This happened to me once. I flatted on the road, changed tube and filled with CO2 to get home. Next day, I checked pressure as I usually do before my ride and saw it was a bit low (maybe 85psi). I pumped it to 115 psi and got ready for my ride.

On my way to get my bottles, I hear that loud 'bang'. The tube burst and the sidewall of the tire was off the rim as well. Not sure if mixing CO2 and regular pump air (excuse the ignorance) caused this. But it could have also been improper tube installation on the road the day before. Since then, if I filled with CO2 on the road, I deflate it completely once I'm home...then re-pump. Never had the issue again.

Definitely a misinstallation. CO2 diffuses through butyl rubber ~20X faster than Nitrogen (which is what air is mostly comprised). That's why you noticed the lower pressure than normal the next day.

BTW, CO2 diffuses through latex even faster. That's why if you run latex tubes and use CO2 for fillng flats, it's a good idea to carry a butyl spare tube.

 

[Mark McM]

Cause and affect

I was once pumping air into my wife's commuter bike when that happened, and it was right in front of me too. The loud BANG was indeed extremely impressive. Left my ears ringing, and bent the crappy rim that was in it too! The force was pretty bloody impressive.

Neither a pinched tube nor a blow out can cause a rim to bend (assuming the rim was strong enough to hold the pressure of a correctly installed tube). A blow out does not cause an increase in force on the rim - just the opposite in fact, the loud bang is from a sudden decrease in pneumatic force.

But the opposite is quite possible, a suddenly failed rim can cause a blow out. A rim sidewall that has been damaged or worn down from braking can suddenly let go, and the sudden lack of support can cause a tube blow out. If you discover a bent rim sidewall after a blow out occurs, it is likely that the rim failure precipitated the blow out, and not vice-versa.

 

[fisherman]

Mark, you are most probably right. Could not figure out how the force would have bent that sidewall. Just a tad, but still, you could see that it was bent. Probably from hitting the kerb at low pressure one time too many!

I did not want to pump my tyres for a couple of weeks after that btw. ;-)

 

[lebikerboy]

I had a few problems with pinched tubes a while back with my new Mavic CXP 33 rims, Velox tape, Continental tubes, Schwalbe tires and decided to try talcum powder in the tires so that the tubes were more like to seat inside the tire correctly. Works like a charm.

 

[Thorn Bait]

I have never had a pinched tube be able to last more than a few moments at full pressure without blowing. How could he go 80 miles on a pinched tube?

 

[Al1943]

I have never had a pinched tube be able to last more than a few moments at full pressure without blowing. How could he go 80 miles on a pinched tube?

It happens, like the others have said, when there is a very small part of the tube caught between the tire and the rim, not the side of the rim but the bottom, where the Velox is. After installing a tube and before adding air it's best to check all the way aroung both beads to make sure the tube is completely inside the tire.

 

[CycleRaff]

I have never had a pinched tube be able to last more than a few moments at full pressure without blowing. How could he go 80 miles on a pinched tube?

Definitely happens. One morning, after quickly installing a new tire, I went for a quick 20-miler. In the shower, I hear a loud BANG from the hallway. Check out the bike after the shower and see the same scenario as mentioned by the OP. In my haste to get my ride in before going to work, I must have been sloppy mounting the new tire (which, being new, had been difficult to seat. Noticed no lumps, etc. in the tire prior or during the ride. Just glad that the blowout didn't happen during the ride.