tube tear at valve stem base — any ideas why and how to fix?

[J J]

Hi, I was inspired by Matthew's "Patch or Replace Tire" thread, but didn't want to usurp it with my question/issue, so I'm starting a new one. 

My tire went flat during a recent ride on my Hunq. Upon inspection I saw that there was a tear near where the valve stem attaches to the inner tube. No biggie. I replaced the tube with a spare, got back to riding, but within 15 minutes, another flat. Same tear in the same location. I replaced the tube with yet another spare. This was starting to feel weird. The same thing happened within a few more miles, another tube gone. 

I had no more spare tubes, but a buddy gave me one that is specced for narrower tires. I managed to get back home without incident.

The attached pic shows where the tear occurred in each instance.

But three flats on a single ride! I replaced the tubes the way I always do. Nothing dramatic about it. I used a pump to inflate two, and a C02 cartridge to inflate another. I snugged the valve nut like I always do, not too tight, not too loose. I handled the valve stem carefully, no jerking or bending it. The air pressure was about medium, not too high, not too low. 

I used three different types of tubes, one a Schwalbe, another was a no-name, and the other was a Teravail. I inspected the 50mm Schwalbe Marathon tire carefully and found nothing of concern, no glass, screws, metal, shards, etc. The Lesnik-built wheel itself had run fine for many, many miles with no issues, no flats, nothing, and is in excellent condition. I had been riding on smooth pavement when the flats occurred, and there was nothing remarkable on the road.

But suddenly, on that day, all inner tube hell broke loose. I'm stumped. I don't know what to do differently so I've been thinking about the saying (misattributed to Einstein): "Insanity is doing the same thing over and over again and expecting different results."

I'd be grateful for any ideas you might have or experiences you can share. 

Thanks!!

Jim

[Ryan]

I'll be interested to hear what others say about this...I should check my X0-1's inner tubes  which has been plagued with mysterious flats and at no time have I been able to find anything embedded in the tire or issues with the rim i.e. protruding spokes. In a lot of cases, I would make it home from the ride , but when I went on a ride the next day, the front or rear tire would be flat. Tires are 26 X 1.5 Compass McClure Pass and I've been cursing them , probably unfairly.

Interesting that the tube specced for a narrower tire got you home and I assume it's still not causing flats?

[J J]

Thanks, Ryan. Yes, the narrower tube got me home, but by that point it was only a short 1.5 miles away. I'm not confident that the narrow tube will be ok on a greater distance because I burned through three tubes of varying makes and specs. I'm riding different wheels until I sort this out.

[Brian Turner]

These type of flats are basically the only flats I've received in the past decade or so - mostly because I am very particular and adamant about checking my air pressures before riding. As such, it has caused me to retain tubes for probably longer than most folks, and I'm assuming that has in turn led to issues with the tubes degrading there at the base of the valve stems. That said, it is very odd that you had three such flats in the same ride... very curious. I'm sorry that happened to you, and hopefully you can find the source of the issue!

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[Ian]

I have had similar issues on a one bike. it turned out that the tires which where a tight fit developed a split. So as you inflate opens traps you tube and down she goes.

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[Patrick Moore]

#1: tubes degrade with age. My experience says "no," at least gauging "age" by single decades. Pre-sealant I routinely rode tubes with up to 3 dozen patches accumulated over many years and they worked as well as new tubes. If a tube was 50 years old I'd look at it more than quickly and casually, but "old" applied to tubes, IME, is a very generous term.

#2. Skinny tubes in fatter tires. For a while I used 23-25 mm tubes in 42 mm tires and they worked well. The skinnies were ultralights, too. "Well" instead of "perfectly" because my use involved sealants and OS regular did not seal as well in a skinny tube against a goathead puncture as well as it does a 40 mm tube, also extralight -- the stretching must make the hole a bit bigger.

But since punctures sans goatheads are, glass-strewn dowtown streets apart, so rare, skinnies in fatters can work well. (I've used 1" tubes in 2" tires and 26" tubes in 29" tires, briefly but successfully.

Back to the initial query: IME, bad manufacturing can be a cause of such splits, but the OP had the problem with several different makes.

[John P. in SF]

Hi.

If what is happening to you is what happened to me, your tire is rotating on the rim. 

This sometimes happened when I was using an undersized tube like Patrick M. mentioned, but it happened a lot to me when using modern tires on older rims, and less when using a tubeless compatible rim. Flats generally occurred when riding somewhere that involved heavy braking, and occurred on around three different bikes I have or have had. Like the one time I got a front flat at this spot.  I sometimes speculate that the rim heating up somehow aids with making the tire rotate, which then tears the stem, but that is just a guess.

Moving to a tubeless setup was the only cure I found.

[Jim Whorton]

I had the same thing John P describes, tire rotating in rim, tugging the tube along, causing the valve to tilt then tear at the base.  I also had it happen twice in a day until I decided I was running the tires at too low a pressure.  Increasing PSI solved the problem.  

Jim in Rochester NY

[iamkeith]

I began having this problem frequently, about 5 years ago.  Nothing else about my skills or habits or rims changed from the previous four decades, so I've concluded that there is likely a manufacturing issue.  Thinner/less/more brittle rubber at the base of the stem or something.  There have always been the occasional "slices" due to tube rotating around the rim, or due to too-sharp edge at the valve stem hole on an aluminum rim, but this is different, and happened like you describe, one tube after another.  I could be wrong, but I don't think it's possible to fix them.

Knowing that doesn't help solve your issue though.  Here's what I started doing, and it's pretty much solved the issue for me:

When you install a new tube, keep the knurled nut on the stem, snug it lightly, and install the tube with the nut INSIDE of the rim.  Keep the nut from the old tube, and intall on the outside of the rim, the normal way, and snug firmly.  This will ensure that only the metal stem will ever contact the sharp or abbrasive part of the hole in the rim, which is now sandwiched between two nuts.

[J J]

Thank you, @Brian Turner

@Ian, I rechecked the tire carefully for splits and structural damage. Nothing.

@Patrick Moore, tubes with 36 patches!?! I'm very impressed. That reminds me of the Ship of Theseus paradox: if a tube has so many patches, is it still the same tube, and if it is not, at what point (i.e., which number of patches), did it cease being the original tube and become something else? :) Didn't all that patching cause a lumpy ride? As far as tube sizes, I have historically been pretty lax about matching tube size with tire size, and I haven't had trouble over the years. Bigger and smaller, they worked ok. In this case, though, the tubes were in the right parameters for the tires, except for the last narrow one I used. All of the tubes were fresh and new, nothing old that could have deteriorated.

@John P in SF, I was going to ask how you prevent a tube from rotating on the rim until I saw that your solution was to go tubeless. Tubeless is a nonstarter for me at this point because I don't feel like buying yet another set of wheels. All of my wheels are tube only. Plus my inner tube habits die hard. Also, I wasn't doing any hard braking. The flats happened on level pavement at a moderate pace.

@Jim in Rochester NY, interesting that additional pressure solved your problem. I was running normal for me pressure, medium, like I always do.

@iamkeith, your idea of using the nuts inside and outside makes so much sense. I will try it. It's consistent with what Rich Lesnik suggested to me separately, that valve holes can be sharp and cut the tubes. He suggested that I check the tape near the hole. It's plausible in light of the fact that the tears were all in the same place on the various tubes. 

So I will try the two-nut method, attempt to file or sand sharp edges or burrs on the valve hole itself, and check the liner tape. 

I'll report back here. But first I need to restock my spare tube supply just in case!

Thanks so much to all of you (and to Rich!) for the feedback and help. I very much appreciate it. 

[Garth]

I suspect the metal at the valve hole also. I've never had such an issue as the Mavic rims I've been riding for the last 23 years came with plastic stem hole grommets so they could be used with either type of valve. Presta valve stems fit in very snugly, no play. Thus, enlarging the hole to Schrader and using the plastic grommets is always an option. The plastic grommets are slotted also, allowing them to expand as the presta valve must literally be pressed in, that's how good of a fit they are, as least the ones Mavic uses. 

If you try to deburr the presta hole first, a rotary tool at low speed with a tapered sanding bit ought to work well, as well as countersinking drill bits. Like these from HF ! https://www.harborfreight.com/power-tools/drill-driver-bits/woodboring-bits/countersink/countersink-and-deburring-tool-set-3-piece-61629.html

 I think even if I did that I'd still do the suggest double stem nut idea to hold it in place. 

[Anthony Beauchemin]

Sounds like a problem with the rim or rim tape. I'd replace the tape and inspect the valve hole for any burrs or things like that.

[J J]

Thanks, Garth and brainsarescary.

After riding about 50 miles on that wheel and tire, I’m happy to report that I did not experience another flat. I used the two-screw method, a valve screw inside and outside the rim, and I filed down the sharp edges of the valve stem hole with an off-brand Dremel-like rotary tool and a tapered sanding bit, per Garth’s suggestion. I also added a 2-inch long layer of bar tape (it’s what was handy) over the rim tape across the valve hole, and punched a hole in the tape. 

I believe I can conclude that the tube tear problem is solved. 

Thanks again to all for your help and feedback!

Jim