Help! Exploding tubes

[ridebikeme]

I will also agree that using lightweight tubes can be a VERY big problem!! I have had several blow just like some of you have mentioned... the bike can be standing still and the next thing you know it blows.... Bonty tubes definitely have a problem, and wise to switch to something else. Although I know it's hard to envision that a tube can explode without the tire coming off the rim... it really DOES happen. Unfortunately, tubes can have a weak spot in them, and may not blow for quite some time... I have tested this in the shop, and you can actually see where the weak spot is.... it will expand completely different than the rest of the tube... it may expand larger or be a smaller area. Unfortuantely when a manufacturer has a problem such as this, it not only happens to one tube... it generally happens to a whole run of them... hence you can have the same problem with more than one or not... Anyway, hope the problem is a thing of the past!

[DebW]

I found the following regarding blowouts from Jobst Brandt. Are the Bontrager tubes "short", ie. slightly small in circumference? Could this explain why they blow out frequently? I can believe the superlight tubes fail more frequently, perhaps even enclosed in the tire, but still doubt they would make a loud bang unless the tire lifts off the rim.

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Tire blow-offs were common at a time when "short tubes" were being
offered, tubes so short in their major diameter that they lay flat on
the bed of a rim when stretched onto it, preventing proper tire
seating. Short tubes cost less to make (less rubber) and can be
advertised as being lighter. To test for this condition, push the
casing back from the edge of the rim to see if the tube is exposed.
The tune should not be visible when the tire sidewall is pushed back.
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and
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The creeping blowout that occurs without any exceptional heat, or any
heat at all, is generally the result of a tire that trapped the tube
under the bead on installation. I have experienced this with "short
tubes" that want to lie in the bed of the rim because they are too
small in circumference. These have caused blow-offs while parked as
well as when underway. To test for these, the bead must be pushed
away from the rim wall to assure that the tube is not visible.

Jobst Brandt <jbrandt@hpl.hp.com>

[ridebikeme]

Thanks for the info! The tubes that I have had experience with were NOT short tubes. If you took a tube and put some air into it, held it in your hand, you would see that the tube without a doubt had a weak spot.... one area would be larger or sometimes smaller than the rest of the tube... obviously a definite problem. The tubes that we had problems with were made by Specialized, although I'm sure the same thing could happen with many manufacturers.

So more than likely, the problems with all of the exploding tubes may have something to do with the above and perhaps some are short tubes as you explained....

Have a good riding weekend eceryone!

[melissam]

Deb and Ridebikeme,

Thanks for the additional info. As bike mechanics, you both have more expertise and a wider sample size than the typical bike owner, so your input is extremely interesting.

I don't think the Bonty tubes are short. It's been a couple of years since I've handled one of the Bonty Superlights, so I can't say that conclusively.

Another factor in my case might be the tires that were originally mounted. I don't remember the model of the tire, but it was a Bontrager, very lightweight with no tread. When I had my blow out, one of the guys who was around while I was changing the tire commented on how flimsy the bead was. Maybe Deb's right about the cause in this case -- maybe the tire did separate from the rim due to the flimsy bead.

At any rate, after than incident I switched to the Bontrager butyl tubes and some Continental Grand Prix tires. I just didn't want to take any chances with severe flats, especially with 650C wheels, where borrowing an extra tube could be a problem.

The bummer of the whole thing was that when I first got my bike, I felt like it was the PF Flyers of bikes -- the equivalent of jump higher, run faster. Jobob used to tease me about having helium in the tires. After switching to the heavier tubes/tires, that PF Flyer/helium feeling went away, and hasn't come back since. Ah, the price you pay to avoid flats!

-- Melissa