The Money Mustache Community
Learning, Sharing, and Teaching => Ask a Mustachian => Topic started by: ijingle on December 14, 2014, 09:31:54 PM
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I got a rear wheel flat and patched the tube this weekend. When I blew up the tube to test my patch, I was alarmed at how large the tube got. Look at that monster! I mean, this could fit one of those old-timey bicycles with the giant front wheels.
But, hey, that's the tube that was inside my 700 x 32 sized tire. What is going on here? Is this normal?
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Looks about right.
Fortunately the tires (really, the clinchers) don't expand that much.
Good patching!
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This is normal; the tire constrains the tube. With out the tire, you can blow it up really large (this is actually useful for finding small leaks; the holes get bigger too).
Any way, inflate the tube just enough so that it is about the size of the tire, stick it in there and get the tire on, then finish inflating to the appropriate pressure. Be sure the tire isn't pinching any part of the tube against the rim.
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Yup, totally normal.
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Yep. Normal. I don't inflate them that much though, just enough so that it fits under an inch of water in the bathtub so I can check for leaks.
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When I blew up the tube to test my patch
Maybe this is just superstition, but I try to avoid "testing" the patch like this (blowing up the tube outside the tire), under the belief that such "testing" is pretty likely to actually cause the patch to fail.
1) You can see the divot in your tube where the patch is keeping it from expanding as much as it wants to. That means the tube is trying to stretch under an unstretchable patch, which must put undue strain on the glue.
2) The air pressure inside the tube wants to squeeze out of the hole, and the only thing stopping it is the glue holding the patch in place. When the tube is safely inside the tire, it has both the glue and the pressure from the surrounding tire to hold it on.
So my strategy is to blow it up as big as necessary to find the leak, but once it's patched, don't blow it up again until its inside the tire. I sorta just feel like a patch isn't truly "seated" until it's spent some quality time getting smashed against the inside of a tire.
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Truth be told, I' kinda scared of blowing my tubes up as bit as the OP. Some of them are made more of patch than original tube at this point.
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Yep I blew one apart by pumping it this big. Not sure my ears have ever recovered.
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Keep pumpin' it!! I worked at a bike shop and we'd kick back beers after work and see how big we could get new tubes. Hint: you're only about 1/4 of the way there. :)