Help! Exploding tubes

[AuntieK]

So, I bought a new wheelset, Easton Accent IIs, last Wednesday. I've now owned these wheels for 5 days. In that time, I have had two tubes explode! :eek: (One exploded on front wheel, one on the back). Before they exploded, both made a funny, "twing" noise. Then BOOM!
The tires have a max PSI of 125, and I had them up to maybe 110, so I don't think that's the issue here. Also, when they're exploding, they're in the air conditioned house, so heat isn't an issue.
I was using the Bontrager Super Light tubes, so maybe because of the thinness of the tube? But I've never had one explode with my old wheels, so I'm not sure that's the issue either.
The only factor I can figure that might be a problem is the new wheelset.
Also, one of the tubes only had about nine miles on it, so it's not like they're be too old.
Does anyone have any other ideas?

[SadieKate]

Have you checked each and every spoke and valve stem hole from the inside? Sometimes there is a teeny shred of metal left from the machining. You can clean it up with a metal file.

[AuntieK]

Good idea! I'm going to do that right now.
I'll let you know what I find.

[DebW]

Tubes only go boom when the tire slips off the rim or sustains a sudden large cut. The twing noise you heard was probably the tire lifting off the rim. There is probably a gaping hole in the tube near a sidewall. So somehow either the tires were mounted without the bead being totally seated on the rim, or there is a mismatch between the rim and the tire bead. When you mount a tire, pump it to ~30 lb first and inspect the bead all around on both sides. If an area is higher than the rest, deflate, reset the bead, and inflate again. If an area is low, deflate and try again. Liquid soap can be used in that area to help the bead rise. Only inflate to full pressure when the bead in set evenly all around. If you always do this and the tires still blow, check with your LBS or the rim manufacture for possible tire incompatibility. Checking the inside of the rim is good advice, but usually rim problems cause a hissing noise as the tube leaks, not a boom.

[cusepack]

I've had dreadful luck with bonty tubes . . . when I first purchased my bike, I had roughly six flats within the first month. It wasn't until I changed tube brands, that I stopped experiencing flats. I've been using Conti's for the past 8 months and have only had one flat. My LBS told me that bontrager, for whatever reason, when a "line" of tubes is produced, and there's a defect in one, chances are, that entire shipment will have that same defect. Therefore, on some occasions, they have had to return their bonty tubes (w/ same production line #) when say 5 or 6 riders come in complaining of the same problem. Since my LBS doesn't carry Conti's, I just order them online - they're much cheaper too:)

[AuntieK]

Ok--I took apart my wheels and did a complete inspection, but didn't find anything. Now the only thing that makes sense to me is what DebW is saying about a mismatch between the rim and the tire bead. I took it to LBS today and had it checked out. He said everything looked fine to him too, but if I have further problems, to come back and he'll contact the manufacturer. He also suggested inflating partially, moving tire around a bit, and then filling it up. He's also not all that impressed with super light tubes, so I guess I'll switch to something else (possibly Conti's--thanks cusepack).
Thanks again to everyone for your help on this!

[Deanna]

Maybe the tire guage is inaccurate and it's being pumped up further than you think?

[Pedal Wench]

Did they forget to put in rim strips?

[AuntieK]

Man, you gals are thinking up everything! :)
Pedal Wench, yes, the rim strips are in place.
Deanna, I'll look into verifying the accuracy of the guage, although it was never a problem with the old wheels.
Thanks again, and keep the suggestions coming. I'm still a little uneasy about it, but it has been two days with no explosions, so things are looking up.

[melissam]

AuntieK,

My bike came with Bontrager Superlight Tubes, and all was well until one group training ride, when the front tube exploded. It was a ka-pow sound -- at first we thought someone was firing a gun. The tube died a spectacular death -- there was about a foot long slit in it.

A couple of days after that, I got a flat in another Bontrager Superlight tube while the bike was awaiting a ride.

I decided that Bontrager Superlight tubes were not for me. I tried their non-superlight tubes with better luck, but I just got a flat because there was a non-patchable hole in the valve stem area.

I am expecting an order of Michelin Aircomp tubes -- I'm hoping that they're durable and that I ordered the correct valve stem length. :confused:

-- Melissa

[DebW]

Are you people trying to say that those tubes are so light that they explode with the tire firmly mounted on the rim? If the tire comes off the rim, then any tube will explode, doesn't matter how heavy or light.

[melissam]

DebW,

Yup, that's what I'm sayin'. :)

The first flat I had was when my bike was a few weeks old and had been on several rides. The tires had been mounted by the bike shop. I was shocked when it "blew up." It was loud and completely unexpected. I thought it had something to do with the light tubes and the slick and light Bontrager tires that came mounted on the bike.

Here's what I said about it in a different post on this forum, back in the day:

"And then, while we were riding along Atherton Ave. in Menlo Park, I had the blow out from h*ll. It was LOUD -- KA-POW -- some people in the group thought it was a gunshot. Fortunately, my tire wasn't seriously damaged. (The tube is toast -- about an 8 inch split.) The second fortunate thing is that I didn't have another blow-out, as I'd only brought one spare tube on the ride, and I have 650C tires."

I thought the second flat (after the bike had been sitting in my pickup truck in the mild heat) could be due to heat. Be even so, it seemed pretty sensitive. I switched tubes and tires after that flat.

-- Melissa

[jobob]

I remember that day ! :)

[DebW]

Are you people trying to say that those tubes are so light that they explode with the tire firmly mounted on the rim?


Yup, that's what I'm sayin'.

I'm having trouble believing this, but don't know how we'd prove it either way. Blowouts happen so fast that you seldom see the tire rise off the rim. And they always sound like shotgun blasts. Usually there is no evidence afterward of how or why or even if the tire actually left the rim (though occasionally the tire bead is damaged). But if statistically blowouts happen more often with Bontrager Superlight Tubes, then I'd have to believe it. So far you all have presented anecdotal evidence from 3 blowouts, and that is not statistically significant. I'm not trying to doubt people (you may be right), I'm just being a skeptical scientist (it's my job and my training). If anyone has more evidence or statistics, I'm open-minded.

[melissam]

Deb,

I'm also the scientist/engineer-type and agree that the statistical evidence isn't significant enough to make a case.

However, since I was a victim of the ancedotal evidence, it's enough for *me* to steer clear of the tubes. ;)

It was interesting to see that someone else had a similar experience with the Bontrager Super Lights.

-- Melissa

Let's file a class action case against Bontrager!! Just kidding!!!! :)

[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.

-----------
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.
---------
and
-----------
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