Bicycle Mechanics - Tubes Going Flat Daily
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10-17-03, 05:57 AM
May be an old question I could not find, but I am hoping to find answers to help with problem.
I cannot keep tires inflated. I will inflate to recommended pressures before my ride and within 24 hours they will be either partially or completely flat.
I have 700x25 with 60mm presta valves.
I have tried 2 different brands of tubes ... Nashbar and Bontrager. I have tried "normal" weight and ultralight weight tires. Both me and the local LBS have installed new tubes.
The bike and wheels are only 3 months old.
An suggestions? Ideas?
10-17-03, 06:02 AM
Have a look at the tubes to ascertain exactly where the air is leaking out. It sounds to me like you've either got something very small and sharp embedded in the tyre (thus creating the small puncture), or possibly a spoke poking through the rim tape, which would cause a puncture on the inside of the tube.
If it's the former, the puncture will probably be on the outside (i.e. opposite side to the valve), you might think about replacing the tyre. If it's the latter (thus a puncture on the inside), you should replace the rim tape.
10-17-03, 06:33 AM
It happens on both front and rear tires. I have checked rim tape and tires. Have found no signs nor felt any place of concern.
The leaks are slow. After removing tube I have inflated it and listened for a leaking area. So far I have not found the the spot.
Can you over tighten the small valve on the prestas?
I did see a post about the value of the presta stem ring ... could tightening this be a cause of damage to the presta valve?
I've had same trouble with some tubes they have a slow leak yet you can't find it?
I know that If there Is something embeded In your tire It has to be found and removed or It will always cause problems?If the tube Is old replace couple years
It could be getting porous has well?Anything more then a couple patches on a tube replace also...There Is nothing worse then taking a tire off/on continuely.Good luck with it :eek:
10-17-03, 06:52 AM
Bad luck Oldillini.
The best way to find the leak is to remove and inflate the tube, then hold under water and look carefully for bubbles. With a very slow leak, this is the only sure way to find it.
It is hard to damage the presta valve by overtightening the air valve, but it is possible to bend the tiny stem and cause a mis-alignment in the seal. This could happen if one is not careful holding the pump head during inflation (i have done it myself...). You could use the bubble technique to check for leakage from the valve on a fully inflated wheel/tire and tube.
Hope that helps,
10-17-03, 06:54 AM
Remove your tubes. Put some air in, and immerse them in a bucket or bath of water. Weight them down under the surface. For a std puncture you will see a stream of bubbles. For a very slow one, you may have to leave them for an hr for an air bubble to accumultate.
Ive had cheapo inners go soft after a few days, but good ones hold their air at 90psi for about 2 weeks.
I had a similar kind of problem, and the leak was difficult to locate even when the tube was immersed. I had to pump more air in the tube and "flex" it a bit to get the leak visible. It was on the outside, suggesting that something poked through my outer tyre.
So I checked the corresponding spot from my outer tyre. There was no visible damage on the inside surface and I could not feel anything poking through. On the outside was a small hole, and in the bottom of that hole sat even smaller fragment of glass.
Apparently when the tyre was fully inflated the piece of glass would work its way through the tyre, puncturing the tube. When tube was deflated and removed, the glass would be entirely inside the tyre, making it very difficult to notice.
Good luck with the exercise and be patient. If everything else fails, replace the outer tyre (if the puncture is on that side of the tube, that is).
10-17-03, 08:23 AM
One of the worst problems I have is riding on the side of 4 lane roads where semi trucks travel. All those blown tire fragments you see lying around the sides of the road are full of little wires. These wires arn't much larger than one of my beard hairs. These wires are very hard to find, and even more difficult to locate the puncture site because of the tiny hole they make. The hole is very, very tiny, and often the tube has to be pumped up quite full to find the leak even in a sink of soapy water! :eek:
This is just something I have noticed around here. Good luck!
10-17-03, 09:12 AM
I don't really tighten my presta valves too tight. Just firm finger tight. You don't need to tighten them to make a seal; the air pressure does that. It's more to hold everything in place. Isn't there an O ring in there to make the seal? If you tighten the valve too much you could conceivably deform the little O ring causing a slow leak. Also, do you press the valve in a bit to release a little burst of air before attaching your pump? This blows out bits of grit that might be lurking. Grit on the O ring could interfere with a good seal. The little plastic caps that "serious" cyclists seem to eschew also help keep the valve cleaner.
Try running some cotton along the inside of your tires.
If there is anything protruding it will catch on it.
Both tires? I'd bet you have wire or something imbedded in tire casing.
From my misadventures over the summer, I was having the same exact problem. Flats every morning- it was driving me crazy. I thought my rim tape was fine too, but when I brought it in to a bike shop, the guy told me the rim tape was old and the spokes were protruding through the tape and causing the flats. He replaced the rim tape, and I haven't had a problem since- not one flat. I've done a lot of mileage on my bike. Perhaps if you've also done a lot of mileage, you should replace the rim tape. It's a cheap solution, and if it doesn't work, you haven't wasted that much money, and it never hurts to have new rim tape on your bike.
It sounds like your problem is not the tube as others have stated. Debris in both tires, while possible, is not so probable. The rim tape/spokes get my vote. This, or aliens. ;)
10-19-03, 03:13 PM
Problem persists but I have identified (at least on three tubes checked under water) the location. I am getting pin holes on the outside of the tube (tire side) opposite the valve stem. Same in all three that I have checked.
Still don't know why.
The tires have been removed and rotated around ... if something in the tire I moved it, but the holes are always in the same location on the tube.
Cannot be rim tape because the holes are not on the rim side.
The tubes were different brands, standard weight and ultralights.
Tires are Michelin Dynamics. Could it be tires?
Any ideas?? Maybe it is the aliens.
10-19-03, 04:05 PM
I see glass in there!!!! You have something inbeded in the tire, glass or small wire, that is still working on those tubes. You may have to take the tire off the rim and look for a tiny crack that has glass in it. Push it out form the inside of the tire with the tip of a phillips screw driver pressing against the under side of the offending slit. Those little wires are even harder to find and get out! :eek:
10-19-03, 04:28 PM
Try examining the tyre inside & out with a magnifying glass & a strong light, very frustrating though :( Those bits of hi-ten wire even penetrate Armadillo's some times :mad:
10-20-03, 08:49 PM
in my experience, rim tape problems generally cause much faster flats. definitely do the underwater thing - and if you spend too many hours looking for the issue, just replace your tires (especially if you have spares lying around like me).
You don't allways install the tyres the same way do you? perhaps with the valve hole at the lowest point?
Perhaps there is some loose glass/sharp stuff in the tyre and it allways punctures opersite the valve stem because you assemble or perhaps inflate the tyre with the valve stem at the bottom.
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