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Bicycle Mechanics Broken bottom bracket? Tacoed wheel? If you're having problems with your bicycle, or just need help fixing a flat, drop in here for the latest on bicycle mechanics & bicycle maintenance.

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Old 07-16-03, 05:15 PM   #1
Brennan
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Why did my tube explode?

Just a question that's been bothering me. I put a Specialized Hemisphere semi-slick on my rear mountain bike wheel. The max psi printed on the tire was 80. I pumped it up with my floor pump and when the the pressure got to 60psi...BOOM went the tube. Blew the tire half off the rim too. The tire was within size parameters for the wheel, and the tube was the right size for the tire. I checked the pump's pressure gauge with another gauge and it was off by about 5psi, but still I was well under the 80psi max. Also, the same tire/tube/wheel combo installed on the front was fine. All I can figure is I had the tube pinched or the tire mounted incorrectly, but I thought I had installed it pretty carefully. Any thoughts?
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Old 07-16-03, 05:22 PM   #2
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Quote:
Originally posted by Brennan
All I can figure is I had the tube pinched or the tire mounted incorrectly, but I thought I had installed it pretty carefully. Any thoughts?
I think you've answered the question yourself. Either that or it was a faulty tube.
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Old 07-16-03, 05:25 PM   #3
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I think you've answered the question yourself. Either that or it was a faulty tube.
I concur.
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Old 07-16-03, 05:32 PM   #4
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Perhaps I just didn't want to admit I was careless in mounting the tire. The ringing in my ears should teach me a lesson. Also, I think the blowout did enough damage to the TIRE that it's probably unsafe to use now.
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Old 07-16-03, 06:14 PM   #5
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When you have the tire beads on the rim, always go around the wheel and check that you cannot see any part of the tube between the bead and rim. If you do see the tube at any point, massage it into the tyre casing. Slightly inflating the tube before remounting the tyre can help.

In addition, ensure the section of tube adjacent to the valve is entire within the tyre casing. Sometimes, the valve interferes wthe proper seating of the bead (presta valves mostly) and the tube can get caught there, leading to an explosion.
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Old 07-16-03, 06:21 PM   #6
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Also the rate in which you pump the air in has an effect. Always pump S L O W L Y. I always put in two pumps and rest about 5 seconds in between.
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Old 07-16-03, 07:24 PM   #7
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I doubt that an exploding tube would damage a tire-especially something as robust as a Specialized Hemishpere.
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Old 07-16-03, 08:07 PM   #8
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always pump a bit then let the air out. repeat once or twice. inflate and deflate once before putting the tube in the tire itself. this can help with seating it properly.
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Old 07-16-03, 08:09 PM   #9
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Another possibility is that your pump has an inaccurate air pressure gauge. I had some fun with that on another tire.
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Old 07-16-03, 09:35 PM   #10
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Same problem I had, except the tube didn't explode. I used a car gauge, and it said 40psi on the gauge. BUT the tube was AS HARD AS ROCK! Even when i sat down on the bike, the tube wouldn't bulge or anything. The max it said on the tube was 70psi. Will it even reach 50?!

Matt
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Old 07-17-03, 07:57 AM   #11
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Unless the tire casing itself ruptured, then the ONLY way a blowout (with a big bang) can occur is when the tire bead slips over the rim hook. This can be caused by: (1) tire not on good to start with; (2) tire casing defective as in out of spec or bead damaged; (3) tube pinced under the tire bead pushing it off the rim hook; and (4) damaged rim--bent in the hook area or badly out of round.

It is NOT due to a "defective" tube.

Good luck,
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Old 07-17-03, 09:50 PM   #12
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Check the inside of your tire for cut or mangled cords. If the cords look good, then your tire is almost certainly OK. Hemispheres are pretty tough so it's probably undamaged.

I find that Armadillo tires have a very stiff sidewall and the bead does not always seat easily when first inflated. Usually at around 60 psi I hear a pop as the bead pops into place on my disk brake rims. When the tire is first mounted, the bead on each side of the tire wants to come together in the center of the rim. It would be easy to get a bit of tube caught between the bead and the rim leading to blown tube.

Make sure that you inflate the tube slightly when you install it. Just enough for the tube to hold its shape. This will help keep it up above the rim.

Also, make sure your rim strip or rim tape is in place to protect the tube from the spoke nipples.
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Old 07-18-03, 09:46 AM   #13
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One other thing, a defective tube.
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Old 07-18-03, 09:52 AM   #14
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One other thing, a defective tube.
NO, NO, NO!

A defective tube doesn't hold air or has a slow leak or disfunctional valve.

A tire that goes "BOOM" does so because the tire casing let the tube escape and uncontrollably expand until it pops (the boom). That cannot occur inside the tire casing. Either the casing split open (which would be obvious) or it slipped over/off the rim side, allowing the tube to explode to the side.

A tube, captured inside the tire casing, cannot explode (go boom) unless it is allowed to escape from the casing.

Dave
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Old 07-20-03, 11:08 PM   #15
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If you folks don't mind, I'd like to butt in as this is the problem which led me here in the first place. My recent restoration project has been driving me nuts with this. I've had four blowouts, two on each wheel. The first was from trusting the guage on the pump, the second was from not carefully seating the tire when inflating. But the last two were shortly after inflating the tire to recommended pressure (105 psi) just before a ride. I had been riding for several days before both the last two events.

The bike is a 1983 Schwinn Super Sport built by Panasonic. It uses Araya 700C rims. This is my first road bike in years, and my first ever quality road bike, so I'm not used to working with these high pressures. On this particular rim I don't see a rim hook; it seems to be pretty much a smooth side. For now I'm dropping pressure to 90psi and hoping it will work, but I'm sure taking the cell phone with me on long rides.

I would appreciate anyone's experiance/insight into this problem and apolagize for jumping in, but this is drivin' me nuts. BTW, the bike is a sweet ride.
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Old 07-21-03, 12:25 AM   #16
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Sparks54... is there rimtape on the rims, and have you religiously checked each spoke nipple to make sure no spokes are poking through? Have the holes left by the blowouts been in the same place on the tubes for each tyre? That may help locate the problem. Also, has the weather been hot when you're riding and have you been "riding" the brakes going downhill. Just some thoughts to eliminate.
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Old 07-21-03, 08:18 AM   #17
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Quote:
Originally posted by Sparks54
If you folks don't mind, I'd like to butt in as this is the problem which led me here in the first place. My recent restoration project has been driving me nuts with this. I've had four blowouts, two on each wheel. The first was from trusting the guage on the pump, the second was from not carefully seating the tire when inflating. But the last two were shortly after inflating the tire to recommended pressure (105 psi) just before a ride. I had been riding for several days before both the last two events.

The bike is a 1983 Schwinn Super Sport built by Panasonic. It uses Araya 700C rims. This is my first road bike in years, and my first ever quality road bike, so I'm not used to working with these high pressures. On this particular rim I don't see a rim hook; it seems to be pretty much a smooth side. For now I'm dropping pressure to 90psi and hoping it will work, but I'm sure taking the cell phone with me on long rides.

I would appreciate anyone's experiance/insight into this problem and apolagize for jumping in, but this is drivin' me nuts. BTW, the bike is a sweet ride.
It is possible that those are not hook bead rims--but very unlikely. If the tire has blown off before, it most likely is damaged and will continue to be a problem. I've had that happen once where the tire bead apparently was either broken or stretched and although the tire casing looked okay, you could see it start to climb the rim when pumping it up.

Dave
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Old 07-24-03, 08:37 PM   #18
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Thanks for the fast replies. I haven't been able to check back until today. The rims have new rimtape, a heavy synthetic looking type. Spokes aren't poking through anywhere, but I am having to adjust them as they're new and I think they're still stretching.

The weather has been hot, and the tires blow shortly after inflation. I didn't get to make it to the good hills! The holes and the place where the tires come off the rim don't seem to be in the same place any time. On the first set of tires one did have visable damage to the tire bead.
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Old 08-03-03, 06:49 AM   #19
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Looks like you got your answer but I'll add my 2 cents.... you had the tube pinched between the bead and the rim.... no doubts
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Old 08-03-03, 03:59 PM   #20
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What about the holes that are used to access the spoke nipples. If tehre was the slightest of space where the rubber strip shoulad have been, that would be it too. I once had to put a second layer on my rim with electrical tape because i have the same problem.
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Old 08-03-03, 05:08 PM   #21
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It hasn't gone "boom" in a while now, but I've kept the pressure at 90 psi. The last two times I was ultra careful not to get the tube pinched. I even inflated to 20 psi, then ran the hooks round the rims on both side to see a clear tire seat. I'm sure the rim tape is good becuase its the toughest looking stuff I'v ever seen. I 'll pipe back up if it does it again. thanks all.
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Old 11-02-05, 03:33 PM   #22
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My rear tire has started doing the same thing.

I've got a 1972 Schwinn Super Sport, rims are 27 X 1 1/4. I can put the tire on as gingerly as I'm able to, but no matter what I do beyond 60 psi the tire slowly comes off the rim, and if I let it go far enough the tube will then explode.

My LBS tried also, and it exploded for them too. They suggest a new rim, although there appears to be nothing wrong with mine at all.

So if they don't know why it's happening, does anyone here have any clues?
I'm very frustrated.
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Old 11-02-05, 07:03 PM   #23
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In my adventures I remember coming across information that Schwinn rims used a special tire when they were the 27 x 1 1/4 size. You may want to find a bike shop that has experiance with your classic bike.
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Old 11-03-05, 12:03 PM   #24
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Quote:
Originally Posted by fillthecup
My rear tire has started doing the same thing.

I've got a 1972 Schwinn Super Sport, rims are 27 X 1 1/4. I can put the tire on as gingerly as I'm able to, but no matter what I do beyond 60 psi the tire slowly comes off the rim, and if I let it go far enough the tube will then explode.

My LBS tried also, and it exploded for them too. They suggest a new rim, although there appears to be nothing wrong with mine at all.

So if they don't know why it's happening, does anyone here have any clues?
I'm very frustrated.
You need new rims. If your rims are the originals, then they are straight wall not hook bead rims. Usually you can get about 90 psi on these before you start to have problems, but your rims maybe are a bit smaller, or the tires a bit larger than average. A new set of hook bead rims will lock the tire bead in place and you won't have any more problems with tires slipping off the rims.
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Old 11-03-05, 12:41 PM   #25
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That makes SENSE! I feel better about buying the new rims now.

Thanks for your answer.
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