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Leaky Tube

Old 03-28-20, 06:27 PM
  #1  
edwinxu
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Leaky Tube

Hey guys, I've got a question

I have a tube which has goes flat after one day. I removed it and installed another one (brand new). this one also went flat after a day.

So, I pumped up the old tube and left it there for several days. It held air fine. My question then becomes, is there something wrong with the way I'm putting the tube into the tire? I am sure it is the right width and diameter.

thanks!
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Old 03-28-20, 06:30 PM
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Might be a loose valve core.
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Old 03-28-20, 06:44 PM
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Originally Posted by stevel610 View Post
Might be a loose valve core.
That doesn't explain the new tube leaking, or the old one holding air out of the tire. Beyond that, I got nuthin'.
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Old 03-28-20, 06:44 PM
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Originally Posted by stevel610 View Post
Might be a loose valve core.
My thoughts too. That would be the first thing I would check.
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Old 03-28-20, 06:48 PM
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Submerge it in water, and see where the air is coming out.
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Old 03-29-20, 07:25 AM
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Rather than the valve core, it may be the valve stem.

I had a similar problem once and even put the tube in water and didn't see any bubbles until I touched the valve stem. It didn't take much pressure to open a fissure.

This would explain your tube holding pressure, standing on its own, but losing air when mounted, because if the valve is off-center from the valve hole in the rim, there will be pressure on it, which, in the right position cause it to loose air.

And if the valve hole is rough around the edges or milled roughly, it may cut into any valve stem in a way that would cause a leak until the valve stem is allowed to straighten itself out, as it would standing on its own outside a tire and rim.

And while there may not be anyting wrong with your rim and the valve pass-through hole, there may be a manufacturing defect with the innertubes from that run, or the tubes may have been okay initially, but they may have been packaged in such a way that put pressure on the valve stem causing it to tear...especially if they have sat for a long time before being "unfurled" and mounted.
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Old 03-29-20, 08:44 AM
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If you pumped up the original (leaking) tube without reinstalling it first and saw that it apparently lost no air over a day or two, either the valve is releasing air slowly or (much more likely) the tube has a very small puncture resulting in a slow leak. Check the pressure with a gauge, and you'll find that there's not enough pressure to register. If you were to reinstall that tube and pump it to full pressure, it would lose pressure at exactly the same rate as before.
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Old 03-29-20, 08:58 AM
  #8  
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There are two common possibilities why your NEW tube went flat when you installed it in the tire and inflated it. One is you pinched the tube while installing it making a new hole in a new tube. Did you use the proper tools? There's a video out with Steven Colbert fixing a flat tire. He used a flat head screwdriver. While it works, it makes it a lot more likely to put a hole in the new tube compared to using a tire iron. The other is you did not find the source of the hole in the old tube and it is still in the tire. That will cause a new flat. You can carefully feel around the inside of the tire looking for something protruding from the inside of the casing. The other is to find the hole in the bad tube and match it up to the tire. If you do this, mark on the tire where the valve is located so you can properly match up the tube and tire locations. Do this before attempting to remove the tube. That pretty much finds the place on the tire where you may have something causing the hole. If you pick up a small thorn (goatheads) or a piece of fine wire from car tire steel belt, it can be a devil to see with your eyes but easier to feel if you know where to look.
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Old 03-29-20, 09:10 AM
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Originally Posted by alo View Post
Submerge it in water, and see where the air is coming out.
If a tire takes days to go flat, when you submerge it in water you will see small bubbles. It does not need to be a fast leak.
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Old 03-29-20, 09:43 AM
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Have you inspected your rim strip?
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Old 03-29-20, 11:26 AM
  #11  
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Try this:
  • Remove tube and check for leaks by immersing the tube in water, and also check valve stem.
  • If leak is found, patch it.
  • Check the inside of the tire to make sure there is not something casuing the puncture, e.g., glass, wire etc. Use a cotton ball or piece of a nylon stocking to wipe around the inside; they will snag on the object. The fine wires from automobile and truck tires can work their way into bike tire causing very slow leaks, and they are hard to find in the tire.
  • Check your rim tape and look for protruding spokes.
  • Check the inside of you rim for rough spots, especially where the rim is joined together.
  • Seat one side your tire on the rim with the brand's logo at the valve stem hole. This will help you check the location of puncture casuing objects in the future. When you get a flat, take out the tube, locate the leak, mark the leak, place the tube on top of your tire with the valve on top of the tire's logo, and check the outside and inside of your tire near the location of the leak for the cause of the puncture. If you do not find anything there, flip your tube over and check the other side of the tire.
  • Once one side is seated onto the rim, put a small amount of air in the tube and place it inside the tire.
  • Let most of the air out, and using your hands, seat the other bead on the rim. Many tires tires can be seated without the use of tools. If a tool is nessessary, use a plastic tire iron, being careful not to pinch the tube.
My wife demonstrated the "no tool" tire mounting technique for the bike maintenance classes we were teaching. This is a good video showing this procedure :


Last edited by Doug64; 03-29-20 at 03:45 PM.
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Old 03-29-20, 04:37 PM
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Sometimes fixing a flat tire is like a "garage sale" in the rain. The point of this is: put a couple of pairs of nitrile gloves in you bike's tool kit


Or sometimes is is pure serendipity, like being right in front of a French bakery.

Last edited by Doug64; 03-29-20 at 04:44 PM.
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Old 03-30-20, 06:06 AM
  #13  
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Are the new, 'leaky' tubes latex?
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Old 03-30-20, 07:55 AM
  #14  
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Where do you mostly ride?

My bet, if you ride on public roads, is that you have a "Michelin wire" stuck in your tire. They'll do stuff like that - puncture a brand new tube yet, make such a tiny hole that a punctured tube won't make little bubbles escape so that you can find the hole. Those little devils can be the dickens to find and, once you do find it your problems are just starting because they can also be the dickens to root out.

If it was my bike, I'd examine the inside of my tire real carefully. I've taken to carrying a pair of needle nose pliers with me in my puncture repair kit just for pulling out hose tiny little wires.
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Old 05-13-20, 03:46 PM
  #15  
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Hey, thanks for all the help. In the end i just got another tube and it worked fine.
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Old 05-13-20, 03:53 PM
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Unless it is an obvious object, like a roofing nail (yes, a roofing nail), I always take the tube out so it is lined up with the tire. Then pump the daylights out of the tube. usually I fing the puncture. Then you can retrace to the spot on the tire. That's how I have found the little bitty wires.
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