Bicycle Mechanics - Tire deflates overnight: why?

I'm trying to understand the basics of bike maintenance and I need some help, please. I have a Specialized Tricross Comp bike. I recently changed my rear wheel from the stock Roval wheel to the stronger and slightly wider Mavic A719 wheel. The A719 accommodates tires from 28c-37c. I use the Continental Grand Prix 4 Season 28c tire on my A719 wheel.

Here's the problem: my Continental 28c tire keeps deflating. Four tubes were flat before I realized that I needed to put rim tape. Then, I put rim tape or, rather, what I think is equivalent: I wrapped electrical tape around the rims twice and then I used the slightly thicker Babolat tape - it's a little tougher than duct tape and used to protect the head of tennis racquets - another two times. There is no problem with the spokes puncturing my tires anymore and there are no creases in the rim tape. My inner tubes are no longer going flat.

But then why doesn't the tire pressure hold? I fill it to 115 psi at night. In the morning, the pressure is around 60 psi. After 24 hours, the pressure is at 30 psi. But, here's the thing - no air is leaking. The tube seems to be fine.

Does anyone have any suggestions for what might be wrong?

Thank you so much for your help!

From the amount of pressure you are loosing, it sounds like you have a slow puncture, some pressure loss could be expected overnight, say about 5-10 psi, but not the 55-75 psi you are noting.

Inflate the innertube, and put it in a bowl / bucket of water to see if there is a leak.

did you put the tube in a tub of water? And slowly rotate it through? Slow leaks are hard to find sometimes. While doing this, also check the valve.

You beat me to it!

Yea, and check the inside of the tire . OR little imbedded pieces will puncture the brand new tube.

Last time I had that happen, I found a tiny little piece of steel wire less than 1/8" embedded in the tire punching little holes!

Been there, with the tire puncture slow leak. those little steel wire fragments, from the disintegrated steel-belted tires cast off by 18-wheelers, can be the very devil to find. You have to turn your tire inside out, and drag your fingers or cotton batting across the exposed inner surface of the tire, feeling for the catch where the wire or goathead thorn barely pokes through.

If both tires are losing air (and the pressure can't go down without losing air) then you either have incredibly bad luck or more likely an identifiable problem that needs to be corrected.

Yes, you need to put the tube in water to find the leak, but first mark the tire/tube position on the rim when inflated (you can just mark the tire with perm marker next to the valve hole on the hidden portion of the bead and the tube next to the valve, both on the drive/right side). Then remove the tube and locate the hole. Finally place the tube next to the wheel/tire (drive side up of course). The hole should be in a spot corresponding to the cause if it is a hazard puncture. There are other types of flats, of course - see: http://sheldonbrown.com/flats.html, for the most common. Note that a slow leak can't always be located, but before you replace the tube you need to thoroughly inspect the inside of the rim, the valve hole and the tire bead and casing for anything that might cause a flat. Sometimes very thin wires will not show up as a problem unless the tire is under pressure or from the pressure of pushing from the inside with a cloth over your fingers around the entire inside of the casing (I always did it w/out the cloth but would not recommend that!).

When you remount I advise to mark the right side of the tube and then mount the tires so that the pressure rating is next to the valve (2nd option is the label next to valve). That makes inflation handy for you and mechanics, gives a consistent appearance, and makes diagnosis easier on the road.

If both tires are losing air (and the pressure can't go down without losing air) then you either have incredibly bad luck or more likely an identifiable problem that needs to be corrected.

Yes, you need to put the tube in water to find the leak, but first mark the tire/tube position on the rim when inflated (you can just mark the tire with perm marker next to the valve hole on the hidden portion of the bead and the tube next to the valve, both on the drive/right side). Then remove the tube and locate the hole. Finally place the tube next to the wheel/tire (drive side up of course). The hole should be in a spot corresponding to the cause if it is a hazard puncture. There are other types of flats, of course - see: http://sheldonbrown.com/flats.html, for the most common. Note that a slow leak can't always be located, but before you replace the tube you need to thoroughly inspect the inside of the rim, the valve hole and the tire bead and casing for anything that might cause a flat. Sometimes very thin wires will not show up as a problem unless the tire is under pressure or from the pressure of pushing from the inside with a cloth over your fingers around the entire inside of the casing (I always did it w/out the cloth but would not recommend that!).

When you remount I advise to mark the right side of the tube and then mount the tires so that the pressure rating is next to the valve (2nd option is the label next to valve). That makes inflation handy for you and mechanics, gives a consistent appearance, and makes diagnosis easier on the road.

Also, if I might add, run the cloth through the tire in all 4 directions (around clockwise, counterclockwise, zig-zag across), because sometimes a wire/thorn can be protruding at an angle that may not be caught by the cloth / cotton, or felt by your finger, in certain directions.

You cannot pressure test a tube out the tire, so it sometimes make sense o fill the bathtub to about 10" of depth and put the wheel in at full pressure and see where bubbles are forming. Know that the air can migrate between the tube and tire, but if for example, you see a stream of fine bubbles near the valve, the source is close to there.

Get some decent rim tape for starters. Then try the suggestions here.

Also, if I might add, run the cloth through the tire in all 4 directions (around clockwise, counterclockwise, zig-zag across), because sometimes a wire/thorn can be protruding at an angle that may not be caught by the cloth / cotton, or felt by your finger, in certain directions.

Thanks so much, everyone, for your suggestions. I put the inflated tube in water in the bathtub and no bubbles came out of the tube. The tube is not punctured and the valve seems fine. Further, the tire is new. I ran my hand along the inside of the tire to make sure that there was nothing poking the tube: the inside of the tire is clean. I'm wondering if the 28c tire is too small for the rim (the Grand Prix 4 Season seems to me to run a little small); but it wouldn't explain why the tire deflates. Tomorrow, I will try to put the wheel in the bathtub and see if I see any bubbles. I would welcome so much any other suggestions!

..........I will try to put the wheel in the bathtub and see if I see any bubbles........

I think that's an excellent idea. Testing under full pressure can show a leaky valve that would be missed by just "dunking" the tube alone.

BTW, my 26C tires lose about 15-20? PSI over a day.

Are you using Presta valves? Are you closing them? Use real rim tape.

But, here's the thing - no air is leaking. The tube seems to be fine.


It IS leaking. It has to be.

But you have to be smarter at finding the leak. To leak that much in that amount of time it should be findable by the bubbles methods. It is possible that you have leaky tubes too. There are some made these days that leak no matter what. It has to do with the rubber compounding.

You will find your leak(s).

-SP

Last time I had that happen, I found a tiny little piece of steel wire less than 1/8" embedded in the tire punching little holes!

I had that very issue. One tiny black bit of metal embedded in the tire in such a way as it was almost impossible to see. Let the pressure out, no problems I could see. Inflate the tire? Instant leak. Look at that tred VERY carefully, because sometimes that wire can the hardest thing to find.

If all else fails to resolve the loss, may want to consider if you have a room mate or a neighbor (anyone with physical access to the bike at night) who is not happy with you or is just pranking you.

On the other hand I once dated a nice gal who had the same problem about a decade back. We eventually set up a video cam and found in the end that she was in the habit of not tightening down her presta tubes after filling them... Then all night her cat would wander around and bat at the valves getting a real kick out of the "hisses"... jump back and then sneak up on it again, bat it to get a hiss, repeat until exhausted cat fell asleep. Was one of the weirder bike solution sets I had ever witnessed. Problem was resolve as soon as the owner started tightening her Presta's which defeated the cats fun time... Whenever we had friends over, we would loosen the valves and urge the cat on to everyones amusement. This was before laser pointers came into vogue...

If it hasn't been mentioned, you can inflate the tube a lot, like 2-3 times it's normal diameter, before dunking it. It make the leak bigger and easier to find.

Are you using latex tubes? I doubt that you are, however, if you are, they loose about that much over night.

Just to be thorough... You're not inflating with CO2, are you?

Thank you so much for all your suggestions: you have all helped me out a lot. I inflated the tube as suggested until the tube ballooned. It was then that I found the puncture! I marked it. I took out a previously punctured tube, did the same thing, and marked it also. I then compared the two marks and, lo and behold!, the marks were in the same place. I then put both punctured tubes around the wheel and tried to find the problem on the rim. I could not find it. The puncture seems to be on the side of both tubes and not at the point where the tube touches the spoke.

The problem might be that, as I mentioned, I wrapped electrical tape and nice-fitting Babolat tape around the rim instead of quality rim tape. I cannot see any problem and the rim is smooth, but, when the tube is inflated to high pressure, there might be unwanted friction that causes the puncture. I've ordered rim tape and I will try it when it arrives. I hope that this will solve the problem.

In response to the questions asked:

* I do not use CO2 but a regular pump;
* The tubes that I use are mostly Axiom (Kenda) or Continental;
* The tires are new and not tampered with.

So, the current situation is that I know THAT my tubes are punctured but I do not yet know the source. I suspect that it is the rim tape, although it does not make sense that the puncture would then appear on the side of the tube rather than the bottom where it touches the spokes. I will seek help once more if quality rim tape does not solve the problem.

Thank you all so much - I truly mean that! I'm learning a lot from you.

I had one leak that I found by inflating the tire on the wheel to 30 pounds over the pressure I normally run and putting the wheel into the bathtub with a few inches of water in it. I found the leak was caused by a fine peice of wire that I could't see or feel.

Thank you so much for all your suggestions: you have all helped me out a lot. I inflated the tube as suggested until the tube ballooned. It was then that I found the puncture! I marked it. I took out a previously punctured tube, did the same thing, and marked it also. I then compared the two marks and, lo and behold!, the marks were in the same place. I then put both punctured tubes around the wheel and tried to find the problem on the rim. I could not find it. The puncture seems to be on the side of both tubes and not at the point where the tube touches the spoke.

The problem might be that, as I mentioned, I wrapped electrical tape and nice-fitting Babolat tape around the rim instead of quality rim tape. I cannot see any problem and the rim is smooth, but, when the tube is inflated to high pressure, there might be unwanted friction that causes the puncture. I've ordered rim tape and I will try it when it arrives. I hope that this will solve the problem.

In response to the questions asked:

* I do not use CO2 but a regular pump;
* The tubes that I use are mostly Axiom (Kenda) or Continental;
* The tires are new and not tampered with.

So, the current situation is that I know THAT my tubes are punctured but I do not yet know the source. I suspect that it is the rim tape, although it does not make sense that the puncture would then appear on the side of the tube rather than the bottom where it touches the spokes. I will seek help once more if quality rim tape does not solve the problem.

Thank you all so much - I truly mean that! I'm learning a lot from you.

When inspecting the interior of the tire how do you do it? As some have suggested run a piece of cotton around the inside of the tire, or a piece of stocking/pantyhose.

Also, if you don't already do this. When mounting the tire and tube align the valve steam with the label on the tire. That way it'll be easier to locate what caused the hole.

...On the other hand I once dated a nice gal who had the same problem about a decade back. We eventually set up a video cam and found in the end that she was in the habit of not tightening down her presta tubes after filling them... Then all night her cat would wander around and bat at the valves getting a real kick out of the "hisses"... jump back and then sneak up on it again, bat it to get a hiss, repeat until exhausted cat fell asleep. Was one of the weirder bike solution sets I had ever witnessed. Problem was resolve as soon as the owner started tightening her Presta's which defeated the cats fun time... Whenever we had friends over, we would loosen the valves and urge the cat on to everyones amusement. This was before laser pointers came into vogue...
Oh dear! I had to wipe away tears from laughing so hard! :roflmao::injured: That made my day!

I can totally see my cat doing that. He already dribbles the kitchen cabinet doors like a basketball, and I'm just thankful he hasn't (yet) taken to unrolling the T.P. or repeatedly flushing the toilet.

When inspecting the inside of the tire, stretching the tire inside-out will help, by making hidden problems embedded in the tube stand out better, as the rubber stretches away from the object.

Leak on the side of the tube.... are you pinching it when reinstalling the tire? You might be ending the mounting process at the same place every time..

If you have Schrader valves, check the stems.

If all else fails to resolve the loss, may want to consider if you have a room mate or a neighbor (anyone with physical access to the bike at night) who is not happy with you or is just pranking you.

On the other hand I once dated a nice gal who had the same problem about a decade back. We eventually set up a video cam and found in the end that she was in the habit of not tightening down her presta tubes after filling them... Then all night her cat would wander around and bat at the valves getting a real kick out of the "hisses"... jump back and then sneak up on it again, bat it to get a hiss, repeat until exhausted cat fell asleep. Was one of the weirder bike solution sets I had ever witnessed. Problem was resolve as soon as the owner started tightening her Presta's which defeated the cats fun time... Whenever we had friends over, we would loosen the valves and urge the cat on to everyones amusement. This was before laser pointers came into vogue...

When I was last at the Seattle aquarium with my then still little kids, the guide told the story of the disappearing fish or maybe shellfish in the tanks. They had one tank with an octopus in it. What they discovered by video was that the octopus would leave its tank every night and eat the fish from the other tanks and go back to its own tank afterward.

Also not all tubes are equal. Leak down is going to happen, but some brands of tube leak down more than others. We are told that there are only 4 or 5 tube manuf in the world. However I have found that Bontrager brand tubes seem to have far less air loss than other brands.

When I was last at the Seattle aquarium with my then still little kids, the guide told the story of the disappearing fish or maybe shellfish in the tanks. They had one tank with an octopus in it. What they discovered by video was that the octopus would leave its tank every night and eat the fish from the other tanks and go back to its own tank afterward.

Hey, octopuses/octopi like a midnight snack too . . .

When I was last at the Seattle aquarium with my then still little kids, the guide told the story of the disappearing fish or maybe shellfish in the tanks. They had one tank with an octopus in it. What they discovered by video was that the octopus would leave its tank every night and eat the fish from the other tanks and go back to its own tank afterward.

So the OP needs to video his bike nightly to check for octopi infestation in his house? Never would have thought of that. Makes more sense than a bit of wire or glass in tire or a prank minded feline. ;)