Yup. This is just about as weird as I've seen so far: several tubes, of different brands, material, and levels of usage - all can hold air for days on end, but leak out all their air in a matter of hours when they're inside a wheel. Thick- or thin-skinned, patched up or patchless, brandname or off-brand - doesn't seem to matter. The bubble test reveals no flaws whatsoever.

Could anybody offer an explanation to this?

One tube, you might think of a bad valve. But not lots of them.

My guess is you're just not finding the leak. Put a little more air in the tubes when you have them sitting overnight, or when you are looking for leaks in a bucket of water (2x or 3x their "normal" size)

Those fine radial tire wires can seem almost invisible in the tire, but are like tiny needles.

I'm going with this. Often those very fine wires can be embedded in your tire and pierce the tube when it's inflated. I've found those wires by turning my tires inside out and very carefully examining them.

Yes, something inside your wheel/tire is putting holes in the tubes.

Pump the tube up MORE outside the tire. You want it FIRM. About as firm as those kids bouncy balls, you know the ones that are filled with air and make a weird sound when you kick them and they always fly off in the direction that they're spinning? (The kind used in the somewhat funny clip below.)

I know the clip is weird, but it was the only one I could think of with this type of ball in it.


Also, run your fingers along the inside of the tire. Along every inch. Also, is your wheel missing it's rim strip?

Okay, hold on - is this was the case, shouldn't any given tube be discharging faster when it's outside than installed? This is just it: at least two of the four tubes ive experienced this with will stay all nice and full for days - in one case, weeks - outside. Late last night, I put one of them in and pumped it up to 115 - yes, one hundred and fifteen - psi (Primo Comet rated at 110psi). By early this morning​ it was down to 25. This afternoon, I swapped it out for a brand new tube, and it, too, lost 30psi or so in a couple of hours!

The strip was in place the last time I checked, which was earlier today. And I've had these Primos on for barely a month - they're practically brand new! I'll take the tire off and repirt back, though...

Are they Presta stems? Did you tighten down the presta valve to close the valve?


Has anyone put a curse on you?

Edit~ is the hole in the rim for the stem clean with no burrs or a sharp edge? In the wheel the edge of the stem can be pushed into the hole differently than a tube off the rim. If it's a problem you should be able to tip the valve a lot when the tube is off the bike and get a small leak just from tipping the stem enough.

If it's a presta valve don't tighten down the nut that came on the tube, if there is one. That pulls the tube harder into the hole in the wheel. Just throw the nut away, plenty of tubes are sold with no threads to put a nut onto. IMO the nut just makes it a little easier to fill the tube when using a hand pump.

No. Not necessarily. I'm guessing that you're not pumping it up enough outside the tire for the holes to open themselves up.

I've run into this exact same problem. Tire on bike goes flat. Take tube out, pump it up, no obvious leaks, put it back in tire, goes flat.

So then I pump it up REALLY far outside the tire, and finally find a pinhole. So I look around the inside of the tire and sure enough, there's something pointy in there.

It's a simple system. You are missing something. Try changing the tire. Sometimes the rim strip can get pushed out of place when you mount the tire (I've seen it happen.) Sometimes if you use one of those hard plastic rim strips the edges of the stip can wear a hole in the tube.

Outside you have 1 or 2 PSI
Inside, you have 100+ PSI

The only reason for it to leak quickly when the tube is out of the tire is by over-inflating.

Not counting how well the tubes hold air before putting them in the tire, how well do they hold air after taking them out? Can you locate the new leak in the tubes?

It sounds like you have something causing a flat.. Those thin wires, perhaps a bad rim strip, or a piece of glass you haven't found.

Use some method to mark the valve on the tire (some people align with label or max pressure). Then when you take the tube out, inflate to 3x normal size, and find the hole in a bucket of water. Then go back and inspect the tire at about that point around the tire if on the outside, or inspect the rim if the hole is on the inside.

A cotton ball has also been suggested for finding things like those small wires. I haven't used it, but it is worth a try. Just run it around the inside of the tire and see if it snags onto something.

2manybikes - no, it's a Schrader valve; these are regular BMX wheels (albeit on a folding bike.) And the valve hole was all nice and smooth the last time I checked.

I've just changed out the Primo in question for one of the OE Kenda Kraniums, put in the tube with two patches in it, and pumped it up to 70psi (the Kranium is rated at 65psi max.) I'll see where it is in an hour or so.

So you pump up a tube outside of a tire to 70psi and it doesn't leak as fast as when it's installed inside the tire pumped to 70psi? I am trying to picture this.

And I'm trying to picture what it is that you're picturing - where did I ever say that I "pump up a tube outside of a tire to 70psi?"

i am assuming the wheel has no shards of metal to puncture the tube, especially, by where the tube valve hole is. if this is the case i would just purchase new tried and true rim strip and a new tube and tire and be done with it.

I used to use a cotton ball but have switched to a microfiber cloth; it is bigger so covers more area and seems to snag just as well. Also, turn your tire inside-out while checking; this puts the inside under tension and tends to open up small holes where things like to hide.

I would love to see you try to pump a tube up to 70 psi outside a tire.

From behind bullet proof glass.

there is something left in the tire puncturing the tube when you put it in.

Go find it and remove it.

Most likely measurement errors.

When you take the tubes out to examine, you cannot find the leak? Pump more air, and squeeze the tube while it's submerged.

Since you're getting flats on multiple tubes, it's most likely something sharp inside the tire. It could be something along or inside the rim.

Also possible but less likely(?) is poor technique when mounting the tire--either normal pinch flat or puncture from tire levers.

I'm not getting flats - what I'm getting is tubes not holding air when there are no (discernable) holes in them - i.e. none that I could find even when I tried to be as thorough as I could with the bubble test.

I also did a thorough check of the Primo in question; nothing odd in there.

The tube inside the Kenda is still where it was a couple of hours ago - 70psi.

Those are the really same thing.

I'll say this again: Your other tire has something stuck to the inside causing a flat.

If this were my bike I'd do two things. First, I'd put a new rim strip on/wrap a strip of tape around the rim to cover all of the nipples. Then I'd change tires. That almost 100% guarantees no flats if you install the tire/tube correctly.

A "flat" as at least I understand it in this context is "something punching a hole in the tube out of which the air would escape." Problem is, in this case 1. there are no holes that would show up in a bubble test, and 2. for now, at least one tube - the one with two patches in it - seems to be holding air just fine inside of another tire.

corrado33 - will use electric tape around the rim as soon as I'm done testing.