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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 07-23-08, 03:51 PM   #1
Angus37
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Mysterious Flats?

This is a little embarrassing, but...

The other day I got a flat on my ride in to work. I replaced the tube that night and pumped it up to ~120psi (road bike, btw). The next morning it was completely flat with what looked like a small tear in it.

I replaced this tube with another and only pumped it to ~100psi. Then the morning after, it too was completely flat, with a similar tear!

I've never had problems with changing a flat before, but I'm trying to understand this. It's my first time changing flats on a road bike but I didn't think that would make too much difference.

Any ideas? I'm still shocked by the whole thing; changing a flat shouldn't be this difficult.
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Old 07-23-08, 03:59 PM   #2
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Did you check the inside of the tire to see if there is something stuck in it?
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Old 07-23-08, 04:04 PM   #3
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I did. I felt all through the inside of the tire. Nothing that I could tell. I'll check again tonight when I try to fix it for the third time.
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Old 07-23-08, 04:11 PM   #4
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Make sure the rim has not been damaged or have sharp edges.

Make sure the tire is seated properly. If the tire is not seated properly it will allow the tube to bulge out and burst, making a tear in the tube.
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Old 07-23-08, 04:31 PM   #5
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Can you give us a clue where the tear on the tube is?

I doubt if your not seating the tire properly but start there since it's the easiest thing to do; make sure the tire bead is completly inside the rim and even all the way around on both sides of the rim. Again I doubt this since you mentioned you've had years of experience mounting tires...but never the less do it.

If the tear is on the tire side then run a rag along the inside of the tire, a rag will snag on any small object that your eye or hand may miss.

If it's on the side of the tire then more then likely you may have a rim burr perhaps you accidently nicked the rim with a tire iron? Again run the rag along both sides of the rim. Rim burrs can be easily fixed by simply filing down with a fine file then run so emery paper.

If it's on the inside of the tube then the problem may be with a faulty rim tape or perhaps a spoke is sticking thru just a wee bit. Again run a rag around the inside of the rim.
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Old 07-23-08, 04:45 PM   #6
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I'm also wondering where on the tube the tear occurs.
Is it on the same side as the tire bead that was mounted last?
When I think of tears in a tube I think of damage to the tube during mounting the tire to the rim.
Is it possible that the tube was pinched between the rim and a tire tool?

Al
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Old 07-23-08, 05:29 PM   #7
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This may or may not apply, but have you checked the tire itself? I'm more a street and trail biker, so the bikes I ride have separate tubes and tires, though some racing bikes have the tube and tire as one piece (none I've dealt with though). The beads of most tires I've dealt with have a metal band that helps reinforce the bead, and if that metal band is poking out of the tire, that will tear your tube every time. I've actually had one blow out on me during a ride, too.
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Old 07-23-08, 06:23 PM   #8
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Are you using a frame/mini pump or a floor pump?
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Old 07-23-08, 09:43 PM   #9
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Quote:
Originally Posted by freako View Post
If it's on the inside of the tube then the problem may be with a faulty rim tape.
That's a way, way, way too common problem on relatively new bikes. If the rim strip/tape leaves the tiniest little arc of spoke hole uncovered, air pressure will force the inner tube against the sharp edge and you'll get repeated flats.
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Old 07-24-08, 10:12 AM   #10
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Thanks for all your suggestions and advice. To cap:

Quote:
Originally Posted by freako View Post
Can you give us a clue where the tear on the tube is?
Outside of the tube (against the tire instead of against the rim)

Quote:
Originally Posted by lectraplayer View Post
This may or may not apply, but have you checked the tire itself?
Yes, I have. Nothing in the 2-3 times I have checked it.

Quote:
Originally Posted by jsharr View Post
Are you using a frame/mini pump or a floor pump?
I've been using a floor pump.

Quote:
Originally Posted by Retro Grouch View Post
That's a way, way, way too common problem on relatively new bikes.
This particular bike is an oldie, late 80's or so. The newness wouldn't be a factor.

I took the old tube into the LBS yesterday and showed them the tube, explained my situation. He said that this happened a lot with these tubes (made by Giant) and gave me a new tube to try.

I'm trying to take a more conservative approach with this one. Partially inflated it last night with my hand pump and left the valve open so that if air escapes it has a path instead of creating one. This morning it was still inflated so something is working. I'll fill it up the rest of the way tonight and if it holds until tomorrow I'll put it back on the bike!
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Old 07-24-08, 10:33 AM   #11
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Could be a cut in the tire; some cuts are difficult to locate when the tire is off the wheel, so examine the tire carefully while the tire and tube are mounted on the wheel and the tube is partly or fully inflated. Look for a bulge or a slit in the tire.

I don't quite get why you thought it would help to leave the valve open (presumably you mean you didn't screw down the tiny brass knob at the top of a presta valve) "so that if air escapes it has a path instead of creating one." When the valve is literally open, the tube is flat. When the tube is holding air, the valve is closed.
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Old 07-24-08, 10:35 AM   #12
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I had a situation like this that was cause by a microscopic piece of metal that was lodged in my tire. Took me 3 tubes to find it. My tube wasn't splitting though; it just wouldn't hold air for long.
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Old 07-24-08, 11:18 AM   #13
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When riding your bike always fully inflate the tubes. Reducing the pressure will only increase your chances of having a flat.

Al
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Old 07-24-08, 12:43 PM   #14
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Quote:
Originally Posted by Retro Grouch View Post
That's a way, way, way too common problem on relatively new bikes. If the rim strip/tape leaves the tiniest little arc of spoke hole uncovered, air pressure will force the inner tube against the sharp edge and you'll get repeated flats.
I usually completely replace the rim strip with surgical tape. It stays in place, can be replaced easily, and the cloth in the surgical tape generally means I can turn the spoke nipples without anything poking thru.

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Old 07-24-08, 12:48 PM   #15
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Quote:
Originally Posted by Angus37 View Post
I did. I felt all through the inside of the tire. Nothing that I could tell. I'll check again tonight when I try to fix it for the third time.
One culprit might be a very tiny piece of metal wire from a truck tire that detreaded. The woven wire in the radial tires is very fine and can poke right thru your tire, but will only show thru under high pressure or if ya bend the tire and look closely. Yoiu'll need pliers to pull it out.

When I am on the road on a tour, to prevent this recurring flat hassle while i ride during the day, I often will just completely replace tire and tube, together, when I get a flat (on a rainy day anyway...or if I am in a crap city location). Then I can look closely later at the end of the day.

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Old 07-24-08, 01:02 PM   #16
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Quote:
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I don't quite get why you thought it would help to leave the valve open (presumably you mean you didn't screw down the tiny brass knob at the top of a presta valve) "so that if air escapes it has a path instead of creating one." When the valve is literally open, the tube is flat. When the tube is holding air, the valve is closed.
That's right, the knob on a presta valve. I've been pumping the tire up to 100-120psi at night. When I wake up in the morning it has been flat and I had this hole in my tube. My experience with presta valves is that opening the valve creates a pathway for the air to escape, but the air doesn't all run out. You need to press on the valve to release the air.

I figure that an open valve releases air better than a weak spot in the tube. So if I pumped the tire up and left the valve partially open...aw heck, I don't know anymore. It made sense to me last night when I did it.

Quote:
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When riding your bike always fully inflate the tubes. Reducing the pressure will only increase your chances of having a flat.
Oh trust me, I do. But all of this has happened WITHOUT ANY RIDING. I replace the tube, I fill the tire to pressure, I go to bed. I wake up in the morning, flat tire. No midnight rides involved.
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Old 07-24-08, 01:50 PM   #17
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We have all given you things to look for. If you still can't determine the cause take it to the LBS.
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Old 07-24-08, 06:38 PM   #18
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Well, if you put the tire on with the label at the valve stem you should be able to see about where on the tire is causing the hole. Inspect that area thoroughly. One trick it to take a cotton ball and "swab" the inside of the tire - it'll catch on any imperfection or debris.
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Old 07-28-08, 09:37 AM   #19
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Thanks for all the help. Once I pumped the tube up to pressure it blew after a few minutes. I took it into the LBS and they said the rim tape was wearing thin in a couple spots, so they put new tape on and filled it back up. No problems since!
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