Someone is stealing my air!

[darwin]

Why do bicycle tubes lose air over a period of a month or so? I can see cheap tubes losing molecules due to the cheapness of the tube. But a thorn resistant tube that has a thick wall, I don't get it. You do the old spit test on the valve, nuttin leaking. Put the tube in a tub of water, nuttin. Put the tube back on the wheel, it leaks. Maybe this is one of the greatest mysteries of the universe that isn't yet solved. I know one thing fo shoo, someone is stealing my air. Dude is going to pay for 50 or so years of me having to air up bicycle tires if/when I catch him.

 

[butre]

other than pressure lost to temperature changes (which isn't air lost, just pressure, cold air is more dense than hot air), some of the molecules that make up air are pretty small. oxygen molecules in particular are prone to seep through the rubber. it really doesn't matter how thick the tubes are, since we're talking molecular loss, just the molecules small enough to make their way around the bonds in the rubber are seeping out. if you were to fill your tires with a gas with larger molecules, like propane, then it would take much longer to leak if it leaked at all.

 

[sp1ke]

well answered absolutly right
another example of this process of gas molicules making it through solid plastic ..
if youve ever had a plastic fuel tank and painted it i expect days after filling it up blisters / bubbles appear under the paint ruining the paint job

those are the escaped gasses that have leaked through the tank

1 way to stop a leaking tube forever is to fill it with silicone sealant lol that does actually work but major bodge no air to leak
another way is use a sealing fluid that fills punchures highly recomended may reduce leak through rubber i use slime a green gel with fibers like fiberglass hairs

 

[Henkster]

I'd recommend Michelin Air-Stop, or decent butyl rubber tubes. They loose air much, much slower than the cheapo Chinese tubes that come with the Walmart bikes.

 

[CrazyDan]

Air has hydrogen, helium, nitrogen, oxygen, carbon monoxide and dioxide. Those first 2 are tiny as f#©k, easy to lose through rubber.