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Thread: Tube failure

  1. #1
    CAT4 joe_5700's Avatar
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    Tube failure

    I want to get to the bottom of why I had a tube fail on me on Saturday. I rode my bike to my LBS to get my rear derailleur adjusted because it was still under warranty and also to take a look at some full carbon bikes. My bike was quickly adjusted and I headed back home. The ride is 10 miles each way. I recently put on some Michelin Pro Race 3's with Continental Race Lite tubes. I was extra careful to make sure that the tubes were not pinched by inflating to 1/2 capacity letting the air out etc. and I had rolled at least 100 miles on them without any issues. So when I headed out it was downhill on a rough street, but it was not that rough. At about 24mph I heard the tube burst which sounded like a *** shot. The front tire was partially off the rim and I quickly came to a stop. So quickly that I was still clipped in and fell over. For someone seeing/hearing this they probably thought I was shot. So, what does everyone think happened? Was the tube pinched the entire time? Was it just a rough road? A flaw in the tube? Were the tires over inflated? I pump them up to 110psi according to my floor pump guage. The tube had a split along the seam that was about 4 inches long.

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    Tire failure? It's possible that the bead came off the rim. This would explain the sudden pop of the tube.

  3. #3
    CAT4 joe_5700's Avatar
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    Quote Originally Posted by furballi View Post
    Tire failure? It's possible that the bead came off the rim. This would explain the sudden pop of the tube.
    The bead definately came off the rim. My question is what the cause was. The tires are pretty much brand new with about 100 miles and the rims are Mavic open Pros. I have a Duathlon coming up on Sunday and right now I am a little spooked to even ride my Felt in the event.

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    Beads blow off for one of two reasons. Sloppy fit to the rim, which is rare with quality tires today. And poor seating which is all too common.

    When you mount a tire it's important that it's seated evenly all the way around. The tire is held on the wire or kevlar bead who'se diameter is matched to that of the seat area on the rim, and smaller than that of the flange. You mount or remove the tire by pushing one section to the middle of the rim which has a smaller diameter creating enough slack elsewhere for get over the flange of the rim. That slack must be eliminated by seating the tire evenly around so it can't blow off.

    Usually the problem is near the valve where the base of the tube is thicker, or where you finished mounting where some of the tube may be trapped under the edge of the tire. As you inflate, it lifts the tire instead of pressing it against the rim and blows off.

    Buy a new tube, install it as before and inflate the tire to only 10-15psi (about 1bar) then spin the wheel and watch the molded lines near the rim to see if the tire is seated evenly all the way around, with no low or high spots. If necessary, deflate and massage the high areas along the rim toward the lower areas until the entire tire is perfectly even all the way around. Also look to see that there's no gaps between the tire and the inside of the rim which might indicate a section tube trapped underneath. Now inflate 1/2 way, do a final check then inflate to full pressure.

    BTW- quality tires are made pretty uniformly so if you see the tread wiggle as you spin the wheel it's usually an indicator of uneven seating.
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    CAT4 joe_5700's Avatar
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    Thanks FBinNY. I will inspect the tires to check for low and high spots and watch the lines by the rim when spinning the tires.

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    Adding a little water/soap water will help a tire with tight beads seat in the rim. You can over-inflate by 20% to assist the seating process, then back-off the pressure.

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    I think FBinNY probably got it right. It's possible if you don't inflate the tube at all before seating the tire that the tube gets caught in some small spot between the bead of the tire and the inside of the rim. May not cause any problem with inflation, but as soon as you get some weight on top of the high pressure, this can be enough to get you a snake bite. Always good to lightly inflate your tube before completely seating the tire to make sure the tube gets fully seated inside the tire.

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    Senior Member BCRider's Avatar
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    Sadly there's some combinations where the tires do not seat all that firmly on some brands of rim. The first thing I'd do is check that the tire itself, with no tube, does not have too much "float" on the rim. Also compare the front with the rear. It would not be the first time a bad tire with an oversize bead slipped past the QC process. I've had one such and returned it. It's rare but it can happen. Basically if I were able to slip the bead on with almost no effort and if I could "stretch" or "smooth" the tire with my hands by slipping them around from one side to pull the bead to the flange seat and the other side just slips off by itself I'd be thinking that this is a bad rim to tire combination which will be difficult to center accurately.

    I'd try this with both the front and rear tires to see if it is a compatibility thing between the tires and rims or if one is noticably sloppier than the other.

    But if all seems well then you must have been carrying a "hernia" around without noticing it. I had one like that which lasted most of a day before it let go while I was just doddering along through a park. In this case it was a known fairly loose fit. But it was also a hard to fit Specialized Armadillo with heavy sidewalls that just did not want to stay in place. After much care to fit the next tube this fairly sloppy tire to rim fit has been fine for over three years and many miles.
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    CAT4 joe_5700's Avatar
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    I went home during my lunch break and inspected both the front and rear tires by spinning them and checking the line on the sidewalls as well as the tire heights. Both wheels look good to me. The next thing I am going to check is the pressure with a guage other than what is on my inexpensive schwinn floor pump. I will be getting a Zefal analog guage tomorrow.

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    I had the same thing happen to me last year, exactly as you described. The front tyre blew off the rim at about 15 mph and scared the crap out of me. I replaced the tube and made it to my LBS ( a little shaken). When I checked the rear with the shop pump it was over inflated by about 20psi more than I'd early seen on my own floor pump. Now I check the pressure with a separate gauge.

  11. #11
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    Quote Originally Posted by A.Gronow View Post
    I had the same thing happen to me last year, exactly as you described. The front tyre blew off the rim at about 15 mph and scared the crap out of me. I replaced the tube and made it to my LBS ( a little shaken). When I checked the rear with the shop pump it was over inflated by about 20psi more than I'd early seen on my own floor pump. Now I check the pressure with a separate gauge.
    I wonder if the LBS maybe shot some air in the tires (when they did not need it) while I was looking at the new bikes?

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    Quote Originally Posted by furballi View Post
    Tire failure? It's possible that the bead came off the rim. This would explain the sudden pop of the tube.
    If you hear the tube pop loudly, it's required that the tire have come off the rim. The noise is rapid expansion of air. That can't happen if tube is completely surrounded by tire and wheel, there's no way for air to escape rapidly enough. Improper mounting or extreme over inflation (often caused by excess heat from heavy braking) are the usual causes.

  13. #13
    Used to be Conspiratemus
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    Someone in another thread (DannoXYZ I think) mentioned this so I'll reiterate for him: After you get the tire mounted but before putting any air into the tube, push the bead gently away from you with your two thumbs so it presses against the other side of the tire. Check to make sure you can't see any tube in the well of the rim -- you should see only rim strip if the tube is truly contained "inside" the tire. Go around the entire circumference of the tire, checking every 5 cm, then flip the wheel around and check the other side the same way. Push the valve stem well up into the tire as well, to make sure the bead gets around the tube here especially. If you see even a tiny sliver of tube showing, it will eventually herniate and lift the bead off the rim. Sometimes you have to remove one bead entirely and start over to get that fershlugginer tube in there where it belongs.

    Then proceed to inflate partially as the other posters have said.
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    CAT4 joe_5700's Avatar
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    I remounted both tubes last night due to paranoia. Before I installed the tubes I applied baby powder to them shake and bake style in a zip lock bag. I also installed the tires by hand without using any tire levers. I will follow your advice conspiratemus1 and inspect the tire to make sure that the tube is completely inside the tire. Then I will inflate fully and check with an analog presta bike tire guage that I will be getting over my lunch break. Are folding bead tires just harder to mount or what? I have never had an issue mounting tires before....

  15. #15
    Primate Metzinger's Avatar
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    Folding beads are floppier. So it's easier to get a small bit of it improperly engaged with the rim.
    In general, I find them easier to work with than steel beads.

    Write that tube failure off as a freak occurrence. Pay close attention when mounting tires. But don't let your worries impact your bike split.

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    Quote Originally Posted by joe_5700 View Post
    Are folding bead tires just harder to mount or what? I have never had an issue mounting tires before....
    Generally yes, their Kevlar beads are stretchier than the steel wires of their counterparts, so they're made slightly tighter to compensate.

    I'm a Bronze age rider and prefer steel bead, non folding tires for that reason. For me, lower cost and easier mounting trump the marginal weight savings of kevlar bead tires.
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    It's almost impossible to over-inflate a tire with steel bead. My Michelin City is rated at 90 psi max, but I've kept the tire at 120 psi on Mavic Open Pro 700c overnight without a blow out. The more esoteric tires with Kevlar bead can be touchy when it comes to proper seating in the rim. I like to apply a little water on the bead, pump the tire to 120 psi, then back off to the riding pressure.

  18. #18
    BeaverTerror Yan's Avatar
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    Just be glad you didn't get wasted like I did last month. Front blowouts are very dangerous. I destroyed $350 of parts in that crash and lost a bunch of skin. Had to get a new front wheel parceled from shanghai, as I was on tour.
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    CAT4 joe_5700's Avatar
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    Quote Originally Posted by conspiratemus1 View Post
    Someone in another thread (DannoXYZ I think) mentioned this so I'll reiterate for him: After you get the tire mounted but before putting any air into the tube, push the bead gently away from you with your two thumbs so it presses against the other side of the tire. Check to make sure you can't see any tube in the well of the rim -- you should see only rim strip if the tube is truly contained "inside" the tire. Go around the entire circumference of the tire, checking every 5 cm, then flip the wheel around and check the other side the same way. Push the valve stem well up into the tire as well, to make sure the bead gets around the tube here especially. If you see even a tiny sliver of tube showing, it will eventually herniate and lift the bead off the rim. Sometimes you have to remove one bead entirely and start over to get that fershlugginer tube in there where it belongs.

    Then proceed to inflate partially as the other posters have said.
    I think I may have discovered the cause of the problem. I let out all the air from both tires and the front tire looked good, but the back tube was not all the way in the tire. I could see some tube right where the valve was on both sides. I simply pushed the valve up and it went in and was "loose". I ended up buying an SKS digital pressure guage. The analog Zefal one just looked cheap and I'd rather have digital for like $3 more. It turns out that my Schwinn floor pump was dead on so it was not a tire pressure issue. Just user error. Thank you everyone for posting and helping me out with this. I have learned my lesson from this and thankfully I didn't wreck from this happening.

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