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Bicycle Mechanics Broken bottom bracket? Tacoed wheel? If you're having problems with your bicycle, or just need help fixing a flat, drop in here for the latest on bicycle mechanics & bicycle maintenance.

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Old 05-24-11, 11:34 PM   #1
MotobecaneGT
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mystery flats

so for the past 1000 miles or so ive ridden without getting a single flat. impressive, i thought. then this past week, everything went to hell in a handbasket, and i've been through 3 tubes and a whole patch kit. rear tire of course. each time ive checked the tire for glass or other crap and turned up nothing. the last 3 times ive actually taken the whole tire off the rim to look for stuff, nothing. there is still plenty of tread on the tire (continental gatorskins). the rim doesnt show any signs of damage, and i have a good cloth covering around the nips. the one i got today was the weirdest yet. i put a new tube in this morning, pumped it up to 125psi and rode about 25 miles total, while doing stuff in between the two rides. i got home about 5 hours later and checked the pressure and it read 70psi. i topped it off at 120 so i could determine how fast it was losing air, checked a half hour later and it was at 60. by the end of an hour it was completely flat. why would it lose air faster for no reason? why am i being plagued with these flats at a time i cant afford to take the train?!?

Last edited by MotobecaneGT; 05-25-11 at 12:28 AM. Reason: forgot some stuff
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Old 05-25-11, 04:55 AM   #2
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Simples, if the tire logo is matched to the valve hole (it should be) take the tube out, pump it up, and find where the hole(s) are, submerge in water to find if required. now you can fix them (the hole), and also know where to look for on the rim / tire for where / what is causing the flats.

Remove cause, re-fit tube / tire, pump up, and it should not flat again due to that cause
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Old 05-25-11, 03:16 PM   #3
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it gets weirder. i decided to check my one tube that would consistently lose all its air over 12 hours whether i was riding it or not (-10psi/hour) by putting it in water and found no bubbles. i put that tube back in because i figured a slow leak is better than nothing. i pumped it up to 120 and overnight it lost no pressure. none. that seemed too good to be true, and it was. i rode to school on that tube and by the time i got there (about 40 minutes later) it had lost all but 10psi. how does that happen?
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Old 05-25-11, 03:25 PM   #4
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It is possible to pinch a tube in such a way that the air will come out (you can hear it come out).
Release the pinch, and the tube is completely undamaged (no leak at all). I would look for something that is causing an undue stress on the tube.
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Old 05-25-11, 03:30 PM   #5
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Quote:
Originally Posted by MotobecaneGT View Post
it gets weirder. i decided to check my one tube that would consistently lose all its air over 12 hours whether i was riding it or not (-10psi/hour) by putting it in water and found no bubbles. i put that tube back in because i figured a slow leak is better than nothing. i pumped it up to 120 and overnight it lost no pressure. none. that seemed too good to be true, and it was. i rode to school on that tube and by the time i got there (about 40 minutes later) it had lost all but 10psi. how does that happen?
bad valve....I just had that happen on a tour.
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Old 05-25-11, 03:41 PM   #6
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bad valve....I just had that happen on a tour.
when i put it in water no bubbles came out of the valve?
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Old 05-25-11, 08:51 PM   #7
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Check the tube under water more closely, it's leaking somewhere.
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Old 05-25-11, 09:12 PM   #8
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Originally Posted by MotobecaneGT View Post
so for the past 1000 miles or so ive ridden without getting a single flat. impressive, i thought. then this past week, everything went to hell in a handbasket, and i've been through 3 tubes and a whole patch kit. rear tire of course. each time ive checked the tire for glass or other crap and turned up nothing. the last 3 times ive actually taken the whole tire off the rim to look for stuff, nothing. there is still plenty of tread on the tire (continental gatorskins). the rim doesnt show any signs of damage, and i have a good cloth covering around the nips. the one i got today was the weirdest yet. i put a new tube in this morning, pumped it up to 125psi and rode about 25 miles total, while doing stuff in between the two rides. i got home about 5 hours later and checked the pressure and it read 70psi. i topped it off at 120 so i could determine how fast it was losing air, checked a half hour later and it was at 60. by the end of an hour it was completely flat. why would it lose air faster for no reason? why am i being plagued with these flats at a time i cant afford to take the train?!?
You might have picked up a tiny piece of debris like the wires (as in "steel belted radial") shed from worn out car tires. Those will even go through flat resistant tires (I put one in a brand new Gatorskin).

It hides in the tire until you're riding along, it flexes in the right direction, and the tire punctures. The leak can be tiny so it's hours before the tire goes flat.

Put the inner tube under water, squeeze it, and you'll eventually get a couple bubbles somewhere. Search the tire at that location in bright light flexing it back and forth.

I flatted three times in two days when I picked up a piece of tire wire. Took over five minutes of wiggling to find the thing and I had to borrow my wife's tweezers to dig it out.
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