My friends bike is turning into quite the troublesome mode of transportation...

He's been getting flats at the rate of nearly one per week. Sometimes it will be fine for awhile, and then last tube he managed one whole ride out of (next time he went to hop on it was flat, its done that twice). He's replaced the tires with armadillo tires, and we've checked for anything stuck in the tire, has a thick cloth rim guard with no spoke nipples sticking up, and no dings in the rim lip or inside....

I have no idea what could be causing these constant flats. He's put on tires himself, he's had tires at the bike shop put on. So it's not just shoddy installation either.

Any ideas? Absolutely stumped over here.

He uses it as a commuter bike, and its getting used daily, but i take the same paths as him with zero flats.

I had a rash of flats on one bike some time back. The wheels on this bike took tubes with Schrader valves. The valve hole in the rim tape was just a wee little bit too small, and the valves on the tubes I was using were tapered. This would not allow the tube near the valve to fully seat against the rim. As a result of the tube not being supported by the rim near the valve, the tube would blow out right beside the valve. Sometimes it would take less than an hour, sometimes it would take up to two weeks, but the tube would always blow out and always right beside the valve. This never happened while the bike was being ridden, always while it was parked.

Since figuring out and correcting that problem I haven't had any further flats on that bike.

Hmm, I just looked at the rim tape, and it seems to be a-okay around the valvestem hole. We've also replaced the rim tape throughout this whole process also.

Although we did have a tear near the valvestem during one of the last few tires, but on dunking the last one in the sink, we couldn't find any bubbles even....

Are the holes always in the same place corresponding to the tire or the rim? Is he buying the tubes from the same place? (might be a bad batch)

Possible valve stem problems? Have you tightened the valves inside the stems (Schrader)? I have been using "thorn-proof" tubes of late (much thicker rubber) and have had no flats since putting them on.

Is he running enough pressure? Too little and he could be pinch-flatting.

What kind of holes are in the tubes? Single holes? Doubles?

Have you checked the tube to see if they're puncturing on the tyre side or the rim side?

Is anyone being rough with the valve when pumping up the tyre?

Whenever I pull out a punctured tube I put a little air in the tube and lay it against the tyre to see if there's something in the tyre at that spot.

I allways put a little bit of air in the tube then put it in the tire so it is in nice and smooth and without a single pinch. Some people tend to drive on car tires until the little wires are poking out and breaking off. They are tiny and you cant see them so you have to feel inside the tire for them and they hurt when you find them!

Hmm, we weren't checking the earlier tubes, but the last two don't have holes in the same place. We've had multiple different shops put the tires on, and one of them I've volunteered at and seemed to be very knowledgeable. So i dont think it's pinches or anything.

Even more odd is I cannot for the life of me find a hole on the last tube. Its sitting in the living room with a bit of air in it still and I just cannot find a hole in it. He was riding it, came home, went to hop on about an hour and a half later and it was flat. Strangest thing.
And presta valves. So i know its not just the valves being loose. They're closed all the way down currently.
The last hole I noted was on rimside though.
The rim itself has been the only constant throughout this, and I can't find anything on the rim that would cause this...

Are you sure somebody is not causing the flat as a windup?

Also as mechanicalron mentioned, tiny wires can do it. I had one that was around 2mm and only found it after it flatted me 3 times. I had to use my tiny swiss army knife tweezers to get it out. I missed it time after time, it was in one of the knobby bits of the tire on my MTB. It only pushed through when pressure was put on it from the outside.

If you can find a hole in a tube, put air in the tube and hold it under water. Air bubbles will lead you to the hole in no time.

It is also hard to find a leak in the tube if it is at the valve stem glue area. The tube can sit there for hours with no leakage until the stem is moved slightly.


Try aligning the tire decal with the stem hole of the wheel when installing. After a flat, when you pull the tube and find the hole, then you can set the stem against the tire decal and find out if something is in the tire at that spot.

Gave a bike to a co-worker a few years back and same problem. I intentionally installed armadillos and he flatted all the time. Ended up being air pressure to low and jumping curbs. When I had time at work I would pump up the pressure to keep him good for a week or two.

Best of luck

This is easy to fix. Don't complicate things. When you have a flat, pull the tube out and leave the tire on the rim. Inflate the tube until you find the leak. When you see where the hole is, deflate the tube and match the hole with the spot on the tire using the stem as a guide. You may find a hole in the tire, a sliver of metal embedded, or a spot on the inside where the rim tape is allowing metal spurs to rub through.

When I was in the Navy and stationed in Guam, I had a co-worker who would ride his bike to work every day and park his bike in the breakroom. He also had a problem with flats. He tried everything; replaced the rim tape, replaced the tube, replaced the tire and eventually replaced the entire wheel with no success. As it turns out, another co-worker was letting the air out of his tire everyday. Sometimes the simplest answer is often the correct one (Occam's Razor).

fill the tube with air, then hang it around your neck like a giant necklace. rotate slowly clockwise until you hear the hissing sound. you will hear it.

Thanks for the replies all. We'll keep cracking at it, and I've tried dunking the tire in the sink with still no luck.

We'll keep checking. Seriously stumped over here. I'll report back if I find anything.

Are you using tire levers to put the tire back on? Pinchy pinchy!

Just an observation.... You've said (or at least implied) the flats are:

• not caused by puncture (at least since the Armadillos)
• not caused by bad rim tape
• not caused by improper installation

It seems to me that only leaves pinch flats from low tire pressure (as barturtle suggested). Either it's that or one of the above listed assumptions is wrong.

See, thats why I'm stumped. Pinch flats generally will deflate pretty quickly correct? Its logically the only thing left, but I ride the same paths as him, and I'd like to think he's aired up correctly. He should be running the Armadillo's at about ~120 right?

I do ride the same paths as him, but obviously I cannot say that he's not going over curbs with any certainty. I'd like to not blame the guy as he's been touchy about it lately, but he's one of the few constants in this situation

120 psi should be plenty to avoid pinch flats, so I'd say it's got to be one of the others. I'd look very closely for something embedded in the tire. I had a problem a while ago where there was a piece of glass in my tire deep enough that I couldn't feel it from either side, but it managed to poke out just enough to cut the tube when I was riding -- usually resulting in a slow leak. Finally, I started sticking an awl into all the cuts in the tread and eventually found the one with glass in it.

It occurred to me on the way in to work this morning that you should probably check the inside of the rim for spurs, up along the sides away from the rim tape. Run a cotton ball around the inside of the rim on both sides and see if it catches on anything. Maybe double check along the rim tape while you're at it.

For what it's worth, after I got a lot of flats in the spring with all the winter road debris I installed Tuffy tire liners on the commuters. I haven't had a flat since.

Switch the front and rear tires and see if the flatting follows the tire or not.

Goat head thorns?



It's been my experience that those mofos can get through "puncture resistant" Continental Contact tires, even with Mr. Tuffy liners installed. I've had it happen that I'll run over them, puncture the tube, then they fall/get knocked off the tire before I realize they're there. I hate those g'dmn things.

Of course, that wouldn't explain the rim-side punctures.