How much air should my tube lose?
#26
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I gave the units used, not how much of each. The volume doesn't enter in to the rate of permeation, just the area and thickness, though the pressure loss that represents depends on volume.
If that were true I could just not-patch a punctured tube, rotate the tire around a bit, then inflate it. Air presses up against the tube pretty tightly but not so tightly that air molecules can't move between them.
If that were true I could just not-patch a punctured tube, rotate the tire around a bit, then inflate it. Air presses up against the tube pretty tightly but not so tightly that air molecules can't move between them.
You'd have to get the tube to full pressure instantly for your example to be a test of this hypothesis. Air will always escape easily from an uninflated tube inside a tyre. Also it only reduces the rate, doesn’t stop it. How often do you want to re-inflate it?
Last edited by choddo; 10-13-23 at 09:49 AM.
#27
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I have often inflated tubes with punctures to 100 psi. They lose all that pressure in a few hours, not 40 days, as they would through permation through the tube alone.
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maybe you could soak the tube in a tubeless sealant bath to reduce the time to which it losses air?
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I'm sorry to seem like an adzhole here, but, what is the point of this thread???
The OP offers a calculation whose results match his actual experience, then invites debate. About what?
He mentions that he might be wrong and wants to learn. But he argues with every response.
Later he mentions getting frequent punctures, but that has no relevance to his original question.
Please OP, spare us the runaround, what EXACTLY are you trying to figure out?
The OP offers a calculation whose results match his actual experience, then invites debate. About what?
He mentions that he might be wrong and wants to learn. But he argues with every response.
Later he mentions getting frequent punctures, but that has no relevance to his original question.
Please OP, spare us the runaround, what EXACTLY are you trying to figure out?
Last edited by FBinNY; 10-13-23 at 05:29 PM.
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#31
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You have to think of that first.
I wasn't asking how to reduce air loss, doubt this would work.
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I didn’t mean forget I said anything at all. It wasn’t some sort of admission I was wrong so your “should have thought of that first” is not the first time you’ve misinterpreted what anyone outside your own head is saying.
I meant anything which I had written in that last post, because I decided you aren’t willing to listen so I’m not going to waste any more of my time or yours so edited it out.
I meant anything which I had written in that last post, because I decided you aren’t willing to listen so I’m not going to waste any more of my time or yours so edited it out.
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i doubt your doubts that in doubt it could be an experiment.
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#34
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I calculated the permeability of my tubes to air, and the numbers seem high. Do you see something wrong with my calculation? I measure my 700x28 tube to have a radius of 1 cm, a thickness of 1 mm, a toroidal radius 33 cm, thus has an area of about 1200 cm^2, a volume of about 600 cm^3. Air is permeable to butyl rubber at 2×10^-9 in units of cm, atmospheres, and seconds. (I rounded all these numbers.) I inflate my tires to 7 atmospheres. From this I calculate that it should lose about 2.5 psi/day, 18/week, which seems like a lot - though it is my experience.