Can't find the leak
#1
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Can't find the leak
Feeling dumb about this. Been fixing flats tires for 50+ years but this one isn't getting resolved. Recent 90's Conley MTB. Very clean. Deore components. Came with very recent Kenda tubes and Komfort tires. Am losing 2psi a day out of the rear. Pumped the wheel to 65 psi and submerged it in 6" of water in my laundry utility sink. Don't see any bubbles. Watched it for quite a while. Pulled the tube and pumped it up to about twice the tire size. Not a bubble. I'd like to pump the tube up more. Is there a general rule on how big an unconfined tube can be safely expanded?
#2
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Right up until it bursts. I wouldn't worry about 2 psi a day. Although that is a little higher than what I'd consider normal. You check your tires before every ride don't you? I normally expect to put a stroke or two of floor pump in my tires every other day.
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I'm with @Iride01; 2psi/day is not enough to get worked up about. If it really bothers you, pull the valve core and pour in some sealant.
#7
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The stem was completely under water in the sink. Neve saw a bubble. That was fully inflated inside the tire.
#8
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This is my grab and run a quick errand bike of the 4 I have. Used sporadically. My 2 road bikes have latex tubes so pumping is a daily deal. The Conley front wheel can go for a couple months. I'm just mystified with my leak detection methods and that 2 psi/day doesn't show a bubble.
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You can put your hands in and get a death grip on the entire tube, wait for the water to settle and squeeze and you might get an idea of where the leak is. But do you really want to chase this?
#10
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Also try removing the tube pump it up to big sausage size and stretch a section at a time under water. This makes the hole a little bigger. Also check the base of the stem by wiggling it around under water. Sometimes tears at the base only show up when the stem is moved.
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New tubes are $5
#13
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Mount the tire and inflate the tire to at least 50% Above the max pressure on the side wall and submerge the tire. I have used this method and found a thin wire that acted as a plug and deflated the tube when I removed it.
#14
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Feeling dumb about this. Been fixing flats tires for 50+ years but this one isn't getting resolved. Recent 90's Conley MTB. Very clean. Deore components. Came with very recent Kenda tubes and Komfort tires. Am losing 2psi a day out of the rear. Pumped the wheel to 65 psi and submerged it in 6" of water in my laundry utility sink. Don't see any bubbles. Watched it for quite a while. Pulled the tube and pumped it up to about twice the tire size. Not a bubble. I'd like to pump the tube up more. Is there a general rule on how big an unconfined tube can be safely expanded?
Bottom line: If the tire goes flat overnight, that’s a puncture. If it only drops a little (<10 psi) overnight, that’s just diffusion and you shouldn’t worry about it.
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2 psi per day is about the average for the diffusion rate of air out of a bicycle tube. You won’t see bubbles because the air is coming out at the molecular level through the bulk rubber. The diffusion isn’t linear so you lose more at higher pressure than at lower pressure. But, generally, I expect to have to pump up bicycle tires on a daily basis.
Bottom line: If the tire goes flat overnight, that’s a puncture. If it only drops a little (<10 psi) overnight, that’s just diffusion and you shouldn’t worry about it.
Bottom line: If the tire goes flat overnight, that’s a puncture. If it only drops a little (<10 psi) overnight, that’s just diffusion and you shouldn’t worry about it.
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Disclaimer:
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5000+ wheels built since 1984...
Disclaimer:
1. I do not claim to be an expert in bicycle mechanics despite my experience.
2. I like anyone will comment in other areas.
3. I do not own the preexisting concepts of DISH and ERD.
4. I will provide information as I always have to others that I believe will help them protect themselves from unscrupulous mechanics.
5. My all time favorite book is:
Kahane, Howard. Logic and Contemporary Rhetoric: The Use of Reason in Everyday Life
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#16
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2 psi per day is about the average for the diffusion rate of air out of a bicycle tube. You won’t see bubbles because the air is coming out at the molecular level through the bulk rubber. The diffusion isn’t linear so you lose more at higher pressure than at lower pressure. But, generally, I expect to have to pump up bicycle tires on a daily basis.
Bottom line: If the tire goes flat overnight, that’s a puncture. If it only drops a little (<10 psi) overnight, that’s just diffusion and you shouldn’t worry about it.
Bottom line: If the tire goes flat overnight, that’s a puncture. If it only drops a little (<10 psi) overnight, that’s just diffusion and you shouldn’t worry about it.
#17
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I wouldn't accept a tube that leaks 2 psi overnight on a mountain bike. On a road bike, with skinny tires at 100 psi, I'd exepect that. I run michelin airstop tubes, mostly, my bike with 700X50 tires loses about 2 psi a week (40 psi front, 50 rear). That's checked inside, so temperature isn't an issue. I would expect to be able to find a 2psi overnight leak with leak detection fluid, but maybe not in a sink.
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Picking the Scablands. Washington and Oregon, 2005. Pie and spiders on the Columbia River!
Stuart Black
Plan Epsilon Around Lake Michigan in the era of Covid
Old School…When It Wasn’t Ancient bikepacking
Gold Fever Three days of dirt in Colorado
Pokin' around the Poconos A cold ride around Lake Erie
Dinosaurs in Colorado A mountain bike guide to the Purgatory Canyon dinosaur trackway
Solo Without Pie. The search for pie in the Midwest.
Picking the Scablands. Washington and Oregon, 2005. Pie and spiders on the Columbia River!
#18
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2 psi is within the margin of error of most gauges. Why are you even worried about this? I'm happy with a 5psi range.
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Check the valve where the stem meets the tube. Wiggle it around and check for separation.