So for the second time in two weeks, I have returned to my commuter bike to find the rear tire flat. The first time I had a sense that I might have ridden through some glass shortly before arriving at my morning destination, so it didn't bother me too much. I repaired the flat, and at the recommendation of others, installed a set of tire liners as well. All seemed well. However, I got another flat yesterday, and when I went to repair it, I noted something that I thought was odd. The issue seems to be...

wait for it...

Inside the wheel. Yes, that's right -- when I removed the tire/tube from the wheel, the hole in the tube appeared to be closer to the rim side, (though it might be in the side wall-- I have to admit, I am not 100% confident in my ability to know how the tube sits in the wheel). It is clear that the hole is closer to the side of the tire with the valve stem, rather than 180 degrees opposite (what I believe would be the tread side). The hole was pretty small -- no more than a large pinprick when the tube is inflated.

I dutifully inspected the entire tire (turning it completely inside out, as well as looking closely at the outside) to ensure that there was nothing protruding or poking through anywhere. I used my hands for the same purpose, running the complete circumference, and trying to do a tactile inspection of every surface. I then did the same thing with the rim, ensuring that the spoke cover was complete, in place and unmolested, and ensuring that there was nothing adhering to the inside of the rim. Everything seemed clean, tidy and as it should be.

I went ahead an installed a new tube, paying special attention both to the installation of the liner and the tube itself, ensuring there was no pinch or binding. I carefully inflated the tube/tire, going slow to ensure everything was seated correctly. This morning, the tire remained fully inflated, so everything seems fine. I rode my "long day" 9 miles, paying special attention to the road / path surface, looking for (and taking pains to avoid) debris, etc... I arrived at my destination still appearing to be fully inflated. I have to say, though: I spent the whole ride nervously waiting for the tire to lose pressure, and even feeling some phantom wobbles (at least, I hope they were phantom) The wheels seemed correctly installed, tight, true, etc...

In addition to replacing the tube, I went ahead and patched the hole in the old tube, so today I am carrying two spares and a patch kit. As I mentioned -- I'm feeling pretty nervous. The real test will be when I get back to the bike this afternoon, as both previous times I have arrived without knowing there was a problem with my tire at all. However, both times I had a sense that I might have ridden through some road detritus shortly before my arrival. Today I was extra careful to avoid debris (within my reasonable ability to avoid stuff) but I don't have a completely 'clean' commute.

Anyway, I am curious if anyone reading this can point to something I'm completely missing as a) the source of the puncture or b) in my repair process? The only other thing I could think of this morning as I was riding in was a broken or damaged spoke that was pressing through the spoke liner, but which didn't leave any obvious damage. Is that even possible?

Any advice or tips are appreciated, as I really don't want to have to repair a flat every week!

1) What kind of rim strip (spoke cover) do you have? Those factory installed plastic or thin rubber strips are garbage and should be replaced. I suggest a cotton rim strip like Velox or even the Forte (Performance Bike house brand) works great.

2) Remove the rim strip and look for long spokes. If you've got one poking up 1mm or so past the head of the nipple and you have a weaksauce rim strip, this is likely a point of failure. Easy way to find which ones to check, match up the hole in the tube with the rim location and start searching there.

3) Check for burrs around the inner rim holes. There might be some little bit of metal left from drilling the spoke holes, just covered up by the rim strip.

Thanks! The rim strip is the factory plastic one, and though it feels pretty robust, I'll definitely give it a careful inspection and I'll probably get a replacement next time I'm at Performance Bike, if the Forte one is adequate, as I am happy to remove a potential failure point. I definitely need to check the spokes, and will this evening. Actually, my wife's bike needs new rim strips anyway (to replace the 30 year old originals), so perhaps I'll get some and do a swap (she rarely rides, and never for more than a few miles -- she can live with the flimsier ones).

As to burrs, I didn't see or feel any when I did my inspection before replacing the tube, but I will give it a closer look when I check the spokes and the rim strip.

Thanks for the advice - I do appreciate it.

CliftonGK1 offerered some good tips there. Another tip is to use a cotton ball; slowly run it along the inner tire and rim surfaces - it should snag on anything that's protruding enough to puncture your tube.

Great tip! Thanks.

I've seen so many posts here on recurring flat tires. I've dealt with it at times as well. In the end it will just keep happening until you find the root cause. It can be maddening. Mine have been:

1) burr on the rim. Finally fixed with sandpaper.
2) small hole in the tire which I couldn't see or feel - finally revealed by comparing hole location in two consecutive flat tubes, then close inspection of that area of the tire after pumping it up to full pressure with a new tube, and discovering a tiny tubal protrusion through the hole. I applied a boot to the inside of the tire and it was fine after that.
3) My last learning experience was discovering that a 23cc tube will NOT work perfectly fine in a 28cc tire. This manifested itself as a slow leak. I could ride 18 miles on a perfectly firm tire, only to find it flat 8 hours later when I wanted to ride home. I held the inflated tube underwater and discovered tiny bubbles coming from the rubber seam in the tube - in two consecutive tubes. A subsequent visit to the bike shop revealed that tubes were sold in 28cc sizes. Duh.

Funny you should mention the tube size. I ride an "asphalt" bike (a Kona Dew Plus) which has wider tires -- 700X35 -- but I have a sneaky suspicion that the tube I put in last week was a 700x28-32 instead. I was careful this time and picked up a 700x35-38, so that might also be a factor.

I will also try the full inflation inspection if I get another -- I definitely think there could be a tiny hidden something.

I'm sorry that you've had back luck, but I would like to come in and say that I have been riding 35mm tires with inner tubes rated for 18-25mm for, well, it must be years now. I've had flats in that time, but nothing that couldn't be attributed to punctures or pinch flats.

In my experiences, inner tubes stretch enough to make up for differences in tire size, and I would doubt that the extra 3mm would cause you a flat tire.

I recently had the same issues and noticed the kind of holes you describe on the rim side of the tubes. I replaced the plastic rim tape with cloth and have not had a flat since then.

For those of us without a nearby bike shop, I've found the 3M Nexcare 3/4" fabric tape to be a pretty good substitute. Two layers, covered with a single layer of electrical tape is doing a good job on at least one of my bikes. I have seen the adhesive on the Nexcare soften enough to soak through the fabric backer in really hot weather, so the electrical tape keeps the tube from getting glued to the rim.

I get inpatient on group rides. Everyone is in a hurry. That is when I get pinch flats.. Insert the tube carefully. I pull the tube away from the liner multiple times. As I stuff the tube, be sure it is positioned outward and not twisted about the crease of the bead and rim's edge. I also inflate multiple times to assure it is not twisted.
On my commute bike , I keep my tires new and change liners as needed. Nothing scared me more than having flats in the way to work. My boss would have loved to blame tardiness on my bike, being he disliked me coming to work via the bike. The oddity. California traffic. It was the car where i 'd have the greater worries about not making work on time.

Figure out how often you can afford to be late, then take the car that often and be late every time.