FBinNY 

Another possibility is a consequence of narrow rims.

Either imagine or sketch a cross section on a tire on a rim. It will have an hourglass shape, with a narrows between the large chamber in the tire and a much smaller one in the rim area.

So, when you start to fill the tire, the tube will stretch to fill the tire. Then as th we pressure increases the area spanning the narrows will stretch more as it blows down into the rim. That can over stretch the tube and cause a split.

If thars the case, you might see some stretch marks elsewhere on th we belly side.

There's no sure fix, but using fresh tubes helps, as does using as dry lube between tube and tire. I've also had luck stretching the tube like new balloons before installing (may be voodoo, but SEEMS to help). Also try Inflating to about 10psi and keeping th we tire to encourage the tube to slide within and start blowing down.

Outrider1

More patience than me. The bike is 26 years old. How about some used or even new wheels?

totheDude

Except, this tube lasted for over two weeks. Why would a pinch from tire lever fail after two weeks?

Also, these tires are quite loose, you don't actually need a tire lever, but I need to check with my son, who did the work, whether he actually used a tire lever or not.

maddog34

i told you what two things can cause that sort of failure, and how to avoid that sort of failure. You eliminated one possible cause, added important additional info, then want to discuss it? Quit dwelling on "Why" or "Who", and just Do, Dude.

has your son read all the responses to his flat tire issue? He's the one that actually needs the info.

grumpus

That looks too narrow - it wants to be butted up tight against the edge of the channel, any gap leaves an edge that can chafe the tube.

totheDude

OK, that tape is not available in 11 mm width. I would have to buy a larger size and trim it.

I am not going to do this. I doubt that the very small gaps do anything.

totheDude

Possible. That is my last resort. First, I will try better tubes.

totheDude

Maybe, but I think those were OEM wheels and tires.

FBinNY 

This has nothing to do with OEM or otherwise. It's purely about the shape of the space.

Also, another possibility also relates to how the tire is mounted. Many people try to install tubes straight out of the box, while they're still flat. If this applies, consider that the tube can get trapped under the tire as you lift it over the rim. Then as you inflate, it yanks free and can partially tear in the process.

Keep in mind that your tire and wheel combination isn't rare, with countless people having no issues. So, the n place to focus is what's unique sets you apart. So stay open to suggestions related to your specific installation routine.

grumpus

You'd be surprised how much of a problem a small gap like that can cause - not every time, but often enough.
Rubber tape usually works fine with that style of rim, and is available in 12mm. Velox or similar is really only needed for double-wall/box-section rims.

totheDude

Update: it lasted 21 days. We had another flat on Thursday. Same rear wheel, same side (facing the rim), and about 2 inch away from the valve stem, corresponding to a spoke bump.
Now ordered a better Kenda tube. The saga continues.

ThermionicScott 

Velox is available in 13mm width. You wouldn't need to trim it narrower, it's perfectly fine for the tape to climb up the walls of the spoke bed a bit if that's what it takes to completely cover it.

totheDude

Maybe it isn't very clear from the pics, but the rim has a narrower (~11 mm) lower section and a wider upper section. Adding another layer of tape could be a good thing. I will order some more.

ThermionicScott 

It's totally clear. I have many wheels exactly like this, and what I recommend works. No mystery flats for me.

P.S. Put another way: if the spoke bed is 10mm wide, and your tape is 10mm wide, it would be wide enough only if there are no spoke nipples. The tape needs to be slightly "too wide" to climb over the spoke nipples and still reach from one wall to the other. Hope that helps.

RC_Dub

Great info here. Two other things to try. Shave down / smooth the one troublesome spoke and add a some padding between the rim tape and the wheel. You can put a piece of electrical tape over the problem spoke before the rim tape.

79pmooney

Proper pre-tire mount tube inflate - really easy, requires no tools, can be done out on the road and it is impossible to put to too much air in. How? Inflate the tube with your lungs. I simply open the valve (this works for presta only unless you have a lot more lung power than I do), insert in mouth and blow hard. Close valve so I won't bump it and lose the air. (Once I've started the mount, wrapping my mouth around the rim and through the spokes is too hard. You might be more talented.)

This gives just the right amount of pre-inflate to easily insert tube and mount tire without pinching the tube and easier to avoid pinching if I have to use an iron to finish the mount. On some very tight tires I have to let some of that air out to do the last couple of inches of bead.

This might not be good advice for those who grew up in antiseptic environments. I grew up around cats, horses and 4 siblings. Hygienists would have been horrified but I love the results! Nothing on the valve stem is going to harm me. (But no, I don't share my stems with strangers.) On topic because this simple step has saved me so many pinch flats.

79pmooney

I've trimmed Velox a few times. When COVID hit, finding proper widths was a challenge. I simply bought "wide enough" and trimmed the brand new roll with a very sharp kitchen knife. Now I keep a too wide roll on hand simply so if I realize the night before an event that "this wheel" that I'd been planning on using has an issue, well that roll can fix it!

How OK going up the spoke bed is depends on both the rim and tire. I've had tires and rims where any "climb meant a ridiculous fight to get the wheel on and other combos where I could use much wider rim tapes.and never even notice. (I just thought this up so bear with me but - you could consider rim tape to be like socks. The rim is the shoe, the tire, your foot. So many rim/shoe and tire/fooot combos. Best tape/sock for each combo varies a lot and some simply don't work.)

totheDude

OK, school year started yesterday.
And.... front tire flat just on the first day. Cause: a burst patch. So we replaced the tube with a new Kenda (Chinese, see pic). Tire was inflated to 40 psi.
This morning we have a flat on the same tire we replaced the night before!!
This is clean cut, again on the inner side (towards the rim):



Now I don't know what else to do. Replace tires? Replace rims? Try different tubes?

Iride01 

Did you drill that hole from presta size to be able to use tubes with a Schrader valve? Can't tell from the pic but the edges of the hole look quite sharp and might need some relief. Though that doesn't explain the other flats.

What size tire are you running now and what PSI are you keeping in it? Your valve stem always sticks perpendicular to the rim and points to the hub doesn't it? If not then probably too low a pressure for your rides. Some of the other pics I wonder if your tube is simply moving around inside the tire/rim as your ride. Which again would be too low a pressure.

Though another pic looks like the tube is pushing into the spoke hole. And if that's not from the tape moving to the side, then that might be too much pressure for that instance.

FBinNY 

Thakns for the photo. Your tube is showing EXACTLY what's happenning.

Please take a moment to read my earlier post #26. Now either imagine or sketch the following.

The narrows between the tire and rim's air spaces is the issue. The tube stretches a lot as it blows down into the gap. Your problem is that the area near the valve can't, leaving an unpressurized zone under the tube on either side of the valve.

The reinforced area near the valve can handle that, but the tube just beyond cannot so it blows down, and then back into the gap below the reinforcement.

Over the years I've used various fixes with reasonable success.

The best - and easiest - fix is to be super diligent about pushing the valve back out after mounting. You might fit the tube to the rim without the tire and measuring how much the valve sticks out after mounting, and use that to confirm that you've seated the valve.

2 - Schrader valves on narrow rims are especially problematic, so seriously consider going to PrestaShop.

3 - If neither of the above are an option, you can make a pair of tapered wedges to fit on either side of the valve to create a transition from tube above the narrows to the base of the rim.

4 - Use a dead tube to make a longer reinforced area extending 2" or so on either side of the valve, then bond it to the tube with rubber cement.

Hopefully, diligent valve seating will fo the trick. Otherwise move to other options according to preference and skills. Keep in mind that you're looking for a 100% reliable solution because you only have one spare if you flat on the road, and will be walking if you blow it.

79pmooney

I haven't gone back and read every one of your posts so forgive me if I've missed something.

Are these tires the ones that came on the bike when you bought it? I seem to recall you saying they had a loose fit. If so, buy new ones. If your shop has Panaracer Paselas that would be an excellent place to start. This bike is a commuter, not a weekend project. Kenda tubes are low end tubes. Better presta valve tubes (using the adopter for the valve hole; a shop will know or just about anybody else here - my last schraeder wheel was back in a distant millennium) will improve your odds a lot. I seem to recall the name IRC as being good quality, not very fancy tubes. Be sure the tube is the proper size for the tire. Smaller tubes stretch to a better ride and feel but a tube with a light stretch to conform to the tire is more reliable and will handle unusual stretch requirements better. (Like around the valve.)

Do not use tire irons to mount the tires. Make sure all the bead except the inches you are actually muscling are in the center channel of the rim. Watch that tube and don't pinch it! I push the valve in a lot when I am working the bead into the center so that bead doesn't pinch the tube. Pull it out before inflation (which I often have to do just to get the pump on). I pump up partway, then spin the tire and watch the molded line on the tire just above the rim to ensure it does not wander up and down. (Your bead is doing the same wander.) At that low pressure, you can manipulate the tire with your hands to even out the bead. When good, pump up.

Clincher tires are all about fit and details. They only work when all parts work together.

soyabean

Since you don't know what else to do, this is where you go visit your local bike shop and have them take care of it once and for all.

FBinNY 

While it's likely that a shop mechanic can mount a tube so this doesn't happen, it's only a partial solution.

The OP needs to learn how to avoid this issue CONSISTENTLY. Otherwise, he'll only be OK until he gets his next flat.

So, either he learns to do this, or be ready to call Uber whenever he rides more than a mile from home.

It's a simple case of getting a fish vs. learning to fish.

totheDude

No need to drill. I think this bike came originally with Schrader valves. As you can see, the cut is some distance away from the stem, so this was not the cause of the flats.

Tire size is 26x2. We do our best to have the stems be perfectly perpendicular to the rim, but that's not always possible. Your guess that the tube maybe moving around is a good one. The tire feels big for the rim. In terms of pressure, at first we always inflated to the top value on the tire (55 psi), but more recently we reduced near the bottom value, 35 to 40 psi.

totheDude

I think you maybe on to something. An incompatibility between the tires, the rims, and the tube.