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Old 08-16-07, 09:13 AM   #1
gbcb
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Grrrr... leaking tubes!

I can't figure out what I'm doing wrong. I bought three new tubes two weeks ago, Presta valves, sized 18c-25c, for use with my 23c Ultra Gatorskins. I pumped them up to about 100psi at night, and by the next day (no riding) my rear wheel was flat. I tried replacing the rear tube, and pumped it up to 100psi again.

I didn't ride this bike for about a week and a half after that. Then, before I took it out for another ride, I discovered both tires were down to 40psi. Pumped them up again, and they seemed to hold air... but the next morning, the front was down to 40psi again, and the rear was completely flat.

How can these tubes be giving up on me so quickly? Any ideas?
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Old 08-16-07, 09:20 AM   #2
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When you checked the tube, where was the leak? There must be a leak somewhere. Pump up the tube outside the tire. It would be weird for both valves to be leaking, but I suppose it's possible.

If you find holes on the inside, check your rim strip and check your mounting procedure to make sure you aren't puncturing them yourself with a tire lever or something.
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Old 08-16-07, 09:20 AM   #3
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are these latex? i believe some tube types lose pressure faster than others.
to handle punctures, try a little Stan's tubeless sealant in your tubes. Works like Slime is supposed to.
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Old 08-16-07, 09:23 AM   #4
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That’s normal for ultra thin road tubes. If it bothers you ask for normal or heavyweight tubes. Wal-mart had Airtight brand Bell tubes for a while. They would only lose 5 Lbs a month but they weighed three times more than even regular tubes. I have them on my touring bike and dread the day they need replacement. It's nice to be able to go on a tour lasting a week or two and never need to worry about adding air every day like every one else in the group.
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Old 08-16-07, 09:48 AM   #5
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Try checking for debris inside your tires. If the back is going flat then something is puncturing your tubes. Run your fingers along the inside of your tires and make sure there isn't anything that has punctured through the tire that is puncturing the tube. Do the same for the rim too.

To make things easier pump the tubes that have flatted and submerge them in a bucket of water. Look for air bubbles and determine where in the tires they were located. The culprit/s will be around there somewhere.
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Old 08-16-07, 09:51 AM   #6
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That’s normal for ultra thin road tubes.
that's not normal at all.

take the tube off, pump it up with some air, and submerge it into a pail of water. if you have a leak (which i assume you do) you'll be able to spot it quickly from the air bubbles coming out of it.
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Old 08-16-07, 10:16 AM   #7
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Thanks for the tips. I haven't located the leak yet, but was just baffled that I lost air so quickly... I've never had problems like this before with my other tires and tubes, but I've never run skinny, high-pressure tires before.
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Old 08-16-07, 10:22 AM   #8
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Thanks for the tips. I haven't located the leak yet, but was just baffled that I lost air so quickly... I've never had problems like this before with my other tires and tubes, but I've never run skinny, high-pressure tires before.
Skinny tires can be quite flat prone if you don't take the necessary precautions.

I bought a road bike for cheap, $50, a year ago because the owner got tired of flat after flat. I installed new tubes and it flat right away. I mean as soon as I hit 100 psi I heard a loud hissing noise. It turned out that the edges of the hole in the rim where the valve goes into was SHARP on both rims. A grinding bit and a dremel tool took care of that problem.
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Old 08-16-07, 10:37 AM   #9
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I think that "skinny" tires/tubes seem to lose air quicker than thicker tires because the air volume is lower than a thicker tire.

Assuming that a tire roughly represents a torus, a 23mm tire would have about 1,680,000cubic mm of air, while a 28mm would have 2,512,000cubic mm of air, and a 32mm would have 3,301,000cubic mm of air. Losing the same amount of air in a 23mm and a 32mm tire will drop the pressure in the 23mm much farther than the 32mm because of the larger percentage of air lost. (I hope my calculations are correct)
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Old 08-21-07, 08:24 AM   #10
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Well, I still can't figure it out. I have tried every method I know to check for leaks, and I can't find any... but these tubes just don't seem to hold any air . Are there any stupid presta newbie things that I might not be aware of? It sucks not being able to ride this bike
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Old 08-21-07, 08:37 AM   #11
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New tubes? Have you checked the inside of the tires and the rim tape on the wheels?
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Old 08-21-07, 11:55 AM   #12
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Have you tried the bucket/water method? Check for air bubbles. If none are found and there are no punctures on the tube then maybe its time to try different tubes. What brand tubes are they anyway?

Oh, are you screwing down the nut on the presta valve?
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Old 08-21-07, 12:04 PM   #13
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One thing I found when I was new to presta valves was that I would seat them wrong in the rim. If the valve is not exactly 90* you run the risk of damaging it. This may have nothing to do with your problem but I know I went through a couple of tubes because of this.
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Old 08-21-07, 03:18 PM   #14
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Quote:
Originally Posted by gbcb View Post
I can't figure out what I'm doing wrong. I bought three new tubes two weeks ago, Presta valves, sized 18c-25c, for use with my 23c Ultra Gatorskins. I pumped them up to about 100psi at night, and by the next day (no riding) my rear wheel was flat. I tried replacing the rear tube, and pumped it up to 100psi again.

I didn't ride this bike for about a week and a half after that. Then, before I took it out for another ride, I discovered both tires were down to 40psi. Pumped them up again, and they seemed to hold air... but the next morning, the front was down to 40psi again, and the rear was completely flat.

How can these tubes be giving up on me so quickly? Any ideas?
I have had this problem and its a leak... pump it up, put it in water and you will find where its leaking and patch it...
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Old 08-21-07, 07:37 PM   #15
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Yup, I've already done the bucket thing. No leaks that I can find. They're new Bontrager 18c-25c tubes with longer-than-usual (60mm?) Presta valves. The valve is straight, and the tires, rims, and tape are new. I'm screwing the Presta nut down. What else could it be? I'm completely baffled.
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Old 08-21-07, 09:03 PM   #16
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You got a bad batch of tubes?
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Old 08-21-07, 09:12 PM   #17
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There is that. But I still don't understand how they could lose air without a leak!
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Old 08-21-07, 10:09 PM   #18
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There is that. But I still don't understand how they could lose air without a leak!
All tubes lose air over time. I lose about 10psi/day. But you seem to be losing faster than that.
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Old 08-21-07, 11:24 PM   #19
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All tubes lose air over time. I lose about 10psi/day. But you seem to be losing faster than that.
Yeah, last night my rear tire was flat in 10 minutes. 10 psi/day sounds like a lot to me, but it's quite possible that I just don't know what I'm talking about
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Old 08-22-07, 12:31 AM   #20
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Are you pumping them up with helium?
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Old 08-22-07, 12:58 AM   #21
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Are you pumping them up with helium?
Nah, deuterium all the way.
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Old 08-22-07, 01:10 AM   #22
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I think that "skinny" tires/tubes seem to lose air quicker than thicker tires because the air volume is lower than a thicker tire.

Assuming that a tire roughly represents a torus, a 23mm tire would have about 1,680,000cubic mm of air, while a 28mm would have 2,512,000cubic mm of air, and a 32mm would have 3,301,000cubic mm of air. Losing the same amount of air in a 23mm and a 32mm tire will drop the pressure in the 23mm much farther than the 32mm because of the larger percentage of air lost. (I hope my calculations are correct)
You need to account for the greater surface area of the larger tires: air will escape faster through them.
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Old 08-22-07, 01:12 AM   #23
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You did screw the presta valve down tight after inflating? And put the little valve cap on it?
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Old 08-22-07, 01:13 AM   #24
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Yeah, last night my rear tire was flat in 10 minutes. 10 psi/day sounds like a lot to me, but it's quite possible that I just don't know what I'm talking about
Back to the bucket of water. You are clearly missing a hole somewhere. Make sure you check around the valve stem, as well.
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Old 08-22-07, 01:45 AM   #25
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You did screw the presta valve down tight after inflating? And put the little valve cap on it?
Yup. I checked that several times, but it was done properly. Or maybe not... how "tight" is "tight"?

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Back to the bucket of water. You are clearly missing a hole somewhere. Make sure you check around the valve stem, as well.
I guess so... Hope to have some time tonight!
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