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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 05-20-07, 01:20 PM   #1
wroomwroomoops
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Tube deflating for no good reisin!!!

Today I wanted to go shopping with my urban SS, but notice the fronttire is flat. Take off wheel, remove tube that is still slightly inflated, so I conclude there is no large hole. Inflate tube some more and put it under water to look for bubbles.

NO BUBBLES!!!!


Facts:
  • 700x37-47C Kenda tube, 1 year old, previously used with some cheap-ass Kenda tire. Schrader valve. (Suomeksi: Autoventiili)
  • Schwalbe Big Apple 700x48C tire, kevlar protected, recommended pressure 30-70 PSI. I pumped it up to 50 PSI. Tire is brand new.
  • Used as front wheel.
  • This setup was used about 10 times, for a total of 250 Km.

Last edited by wroomwroomoops; 05-21-07 at 02:11 PM.
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Old 05-20-07, 01:24 PM   #2
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When was the last time you aired up the tire?
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Old 05-20-07, 01:37 PM   #3
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Quote:
Originally Posted by barba
When was the last time you aired up the tire?
Aired up?

The tire, as I said, is brand new. Now, granted, I don't know what you mean by "aired up", but 1 week ago this tire was still in its shrink-wrap. If that answers your question...?
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Old 05-20-07, 01:52 PM   #4
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Aired-up........inflated..........pumped up........pressurized
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Old 05-20-07, 02:03 PM   #5
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Quote:
Originally Posted by redirekib
Aired-up........inflated..........pumped up........pressurized
1 week ago.
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Old 05-20-07, 02:09 PM   #6
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Presta or schrader valve? Schrader valves are the same as the ones found on cars, presta valves are smaller in diameter and are different internally.
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Old 05-20-07, 02:49 PM   #7
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Kind of hard to diagnose in print -have you reinflated to see what happens? May be a jj flat. (jerk joke - friend deflates your tire for laughs).
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Old 05-20-07, 02:54 PM   #8
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I sympathize with your ordeal.
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Old 05-20-07, 03:24 PM   #9
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Quote:
Originally Posted by redirekib
Presta or schrader valve? Schrader valves are the same as the ones found on cars, presta valves are smaller in diameter and are different internally.
Good question: it's Schrader.
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Old 05-20-07, 03:40 PM   #10
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Originally Posted by cny-bikeman
Kind of hard to diagnose in print -have you reinflated to see what happens? May be a jj flat. (jerk joke - friend deflates your tire for laughs).
I know it's hard to diagnose in print. It's hard to diagnose in vivo, too! But yes, I did try to inflate the tube, as I mentioned in the first post, I inflated it some more (it wasn't completely empty when I took the tire off the rim) and put it under water hunting for bubbles, which I found none. Then I inflated it further - but don't dare to, too much, without a tire around it, for obvious reasons - put it back into water and looked for bubbles. Then I groped this tube in various places. Grope, grope, but no bubbles.

Jerk joke: I thought about this, being the mean Scot that I am (not really, but I do have scottish genes in me), I thought about "the damn kids" when I saw the tire having no holes. However, the problem with this theory is that the front tire was in a place rather difficult to access, while the rear tire was much more exposed, and yet, not deflated at all. If I was to do a JJ on someone's bike, I'd go for the low-hanging fruit. That the vent cap was in place, is perhaps another indication that it wasn't a JJ. Again, as I said, the front wheel was in a hard-to-access place, and just unscrewint the cap would represent some difficulty - not to mention, this is Finland, and people are generally really nice. Furthermore, the bike was in the building's storage room, so only my neighbors had access to it, and there are no "damn kids" in this building, just elderly people, and a few couples with babies. Neither of whom would have the physique, dexterity and motivation to do this. Expecially not the motivation.
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Old 05-20-07, 03:42 PM   #11
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Quote:
Originally Posted by cny-bikeman
Kind of hard to diagnose in print -have you reinflated to see what happens? May be a jj flat. (jerk joke - friend deflates your tire for laughs).
Sorry, maybe I missunderstood you previously: if you meant did I reinflate it on the wheel, with the tire and all - yes, it's there now, on the bike, and I'm checking the pressure every now and then. Seems to be holding.

Damn tubes!
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Old 05-20-07, 03:46 PM   #12
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Quote:
Originally Posted by wroomwroomoops
I thought about "the damn kids" when I saw the tire having no holes.
how could they sabotage the tube/tire without puncturing it?
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Old 05-20-07, 03:56 PM   #13
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Quote:
Originally Posted by mito2008
how could they sabotage the tube/tire without puncturing it?
I take it you were never a victim of a JJ? They deflate the tube by releasing the air through the vent. Fastest done with Dunlop or Presta. A particularly nasty version of JJ is actually removing the vent part of a Dunlop vent. Can happen in Italy (sadly, and I'm half italian, so I can say it).(I do NOT suggest this should be done.)
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Old 05-20-07, 04:37 PM   #14
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got it.... actually, as a kid my gang would do it to cars........ I guess I've become naive....... lol
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Old 05-21-07, 12:34 AM   #15
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UPDATE: I checked just now, and the tire is almost unacceptably soft. I don't think there's even 10 PSI in it. I left the bike in my apartement to have "controlled laboratory conditions" so to say. The tire deflated from about 50 PSI to about nothing in 9 hours.

What the heck?
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Old 05-21-07, 04:11 AM   #16
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Remove the tube, inflate it until it is 1 and 1/2 times its normal size and check for leaks again and make sure to check the valve. If you do find a leak be sure and check the inside of the tire for the culprit.
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Old 05-21-07, 04:19 AM   #17
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Update #2: I decided to use the immersion technique again, added a bit of soap to the water, so that even the smallet bubble is registered, and this time I was luckier with my groping! There's a microscopic leak on one of the longitudinal seams. I am not sure if I can patch this, as the seam has a "contour". Should I even bother? OTOH, the hole is invisible to the naked eye.
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Old 05-21-07, 04:23 AM   #18
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patch it. Why does it matter if its visible or not to the naked eye?
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Old 05-21-07, 04:30 AM   #19
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Quote:
Originally Posted by wroomwroomoops
Update #2: I decided to use the immersion technique again, added a bit of soap to the water, so that even the smallet bubble is registered, and this time I was luckier with my groping! There's a microscopic leak on one of the longitudinal seams. I am not sure if I can patch this, as the seam has a "contour". Should I even bother? OTOH, the hole is invisible to the naked eye.
Sand the seam down, it will patch fine.
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Old 05-21-07, 05:49 AM   #20
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Quote:
Originally Posted by redirekib
Sand the seam down, it will patch fine.
yessir, did just that + medium size patch

Inflated to 60 PSI 1.5 hours ago, let's see....
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Old 05-21-07, 05:52 AM   #21
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Quote:
Originally Posted by thomas_cho
patch it. Why does it matter if its visible or not to the naked eye?
That was the OTOH part, that is, "however, since the hole is so minute, it's worth trying to patch it." Plus, I sanded down the seam, added enough cement and pushed down on the patch like Baby Hulk.

Last edited by wroomwroomoops; 05-21-07 at 07:17 AM.
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Old 05-21-07, 05:58 AM   #22
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A good Reisen!

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Old 05-21-07, 08:13 AM   #23
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A good Reisen!
I was going nuts!

Well, the patch is holding.

So, what I have learned from this: more groping and squeezing!
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Old 05-21-07, 12:29 PM   #24
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Yes, you're correct. With the tube outside of the tyre, there's no structural support so it will barely require any pressure at all to balloon it up. You probably had at most 5psi in the tube and that's why you couldn't find the hole the 1st time. At operating pressures of 60psi on the other hand, a lot more air will escape through that tiny hole.
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Old 05-21-07, 12:53 PM   #25
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Yes, you're correct. With the tube outside of the tyre, there's no structural support so it will barely require any pressure at all to balloon it up. You probably had at most 5psi in the tube and that's why you couldn't find the hole the 1st time. At operating pressures of 60psi on the other hand, a lot more air will escape through that tiny hole.
Well, I'm particularly proud of myself, that I got Danno give the thumbs-up for the groping 'n' squeezing
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