[Excuse my English. I’m German and don’t know all the specific technical terms.]

Today, I tried to inflate my tire, but while taking off the cap, the entire valve rotated with it, as if it wasn’t attached to the tube anymore. But there was still pressure in the tire. So I thought I’d take a look inside.

But the tire seemed glued to the rim. So strongly, that I felt like I almost had to damage the rim, just to get it off.

After opening it, I was horrified, and saw something I have never seen in my 30 years of bicycling: There was no tube anymore on the inside of that tire! It seemed like “tubeless“, and on the inside of the tire and on the rim was a thick, viscous slime, that may as well qualify as type of glue! On the bottom stood a kind of “water”, in a “puddle” of about 1/2 by 3 inches, that smelt of nothing to me, but according to a bicycle technician, smelt pretty badly. Where I had squeezed the tire, it stuck together as if that part was under a vacuum.

Mind you that this bicycle has never seen any “tubeless” liquids. A week ago, there still was a fully functioning tube inside there!

How, for all in the world, is something like that possible??

No bicycle technician that I asked had even seen something like this.


UPDATE: I managed to take pictures!
(adb + scrcpy, in case you wondered.)

Yes… what you see “is” a normal butyl rubber tube. At least what it turned into.

Important: The viscous substance seems to have further degraded, as it looks dryer now and there is more liquid at the bottom. (The brown area.)

Bottom Bottom right Bottom left Overview

Details that may be useful

• The tire is pretty old, and almost a bit crumbly dry, but otherwise fine. Even now, it seems like the tire is re-usable. (After extreme cleaning measures, of course.)
• The tube was fixed by me, about 2 months ago. It got its third, and for me last patch, with a standard tube fixing kit that you get everywhere here, of the same brand I’ve been using for decades. (Containing a tiny tube of vulcanizer, a bit of sandpaper, a couple of patches, some tire levers, etc). I’ve done this many, many times before. It was quite hot on that day (30°C/86°F), and I rode my bike 13km/~8mi to the nearest lake right after. Up until 12 days ago, I used it several times, and everything was fine.
• Then, 12 days ago, I inflated the tire well, the last time, at a machine at a gas station around the corner. I rode 26km/16mi right after. At half the distance, I left my bike attached to a bridge railing in the evening sun for several hours. I rode home after, with no trouble. But I wasn’t really sure the tube was completely fixed and still as hard as it was at the start.
• Since then, the bike just hung on a “bicycle lift” under the roof / on the wall of my hallway.
• I haven’t put any strange chemicals onto or inside the tire or bike. Only a bit of grease for the axle (and only there), and last year I did clean the entire bike with a bicycle cleaning spray and hosed it off thoroughly afterwards.

Additional information

• The bike has never been never close to any cars for longer than a few seconds (while riding on the road) for at least a few years.
• It could not have been standing in a spillage, as I assume then the outside of the tire would be affected, and it is still exactly as it was. (Even now, as I write this.)
• That bridge is in a zone where no cars are allowed and no cars can even get to, due to large boulders blocking the only way. It is going across a highway and mainly exists for wild animals to be able to pass that highway. But people and bicycle riders use it too. It’s a calm and safe place, away from any industry and partially a protected nature zone. So if anything happened there, somebody would have to specifically have injected it through the valve, in front of passing people. I think other explanations are more likely. :)
• The “transformation” might have been already started earlier than we think, but it definitely was still a normal tube and a normal tire when I put that patch on.
• All I keep thinking is “Was something wrong with the vulcanizer?” Because I now remember that the first time, the thin layer was “drying” so quickly in that hot sun, that the patch’s fringes didn’t even stick to the tube. I had to add a bit (a thin film) more ’round the edges, and press it on. I didn’t check it anymore after that, as the instructions said you could already inflate it right after, and I was in a hurry.

  • 4
    If indeed the tire/tube was a conventional tube-style combo, and no chemicals were injected into the tube (and if the bike was not, eg, stored on a concrete floor where chemical solvents were spilled), what you describe is impossible. There is a vague possibility that, when you inflated the tire at the gas station, the pump there somehow contained some chemicals that were injected into the tire. (One slightly plausible scenario for this would be if another cyclist "inflated" a tubeless just before you and fluid from his tire got pushed into the pump.) Commented Jun 30, 2022 at 22:00
  • 4
    I've seen this once before many years ago but in my case not an inner tube. I had tyres on a scalextric car that inexplicably turned into runny goop. Stored in the same place as many other cars that were all fine. I never found a satisfactory answer so very interested to see responses to this thread. Is it possible for rubber to have detrimental impurities added accidentally during manufacture?
    – Andy P
    Commented Jun 30, 2022 at 22:17
  • 6
    Was it a Latex tube? Oil and fat dissolves Latex, perhaps the gas station pump injected oil into the tube (most pumps output tiny amounts of oil). Although the tube's material should be stabilized by additives. You could test this hypothesis by pumping up a Latex glove at that pump ;-)
    – Erlkoenig
    Commented Jul 1, 2022 at 5:16
  • 6
    “Then, 12 days ago, I inflated the tire well, the last time, at a machine at a gas station around the corner.” - did you only use the gas station “machine” on the tire/tube that failed? If so, that could be a clue that the compressed air line might have gotten some contaminants into your tire. Some air systems can have an oiler in-line (used to constantly lubricate air tools) and there may have been the source of the contamination. Butyl or latex tubes are organically based, and the right petroleum products can possibly destroy/dissolve them under the right conditions.
    – Ted Hohl
    Commented Jul 1, 2022 at 5:28
  • 2
    @TedHohl: It was a butyl rubber based tube though. The hint with the lubricant in the “machine” (what’s the correct English term btw?) is a good one. Why didn’t I think of that? Of course there will always a bit of oil in such systems! … But still, if it attacked all butyl rubber, then it would attack the car tires too, no? And as I said, the tire itself seems to be intact and even holding pressure now that it has been made “tubeless” against its will. ;) (The leakage was likely though the valve that was just barely held in place by the goop.)
    – anon
    Commented Jul 2, 2022 at 19:50

3 Answers 3


People saying "rubber won't simply melt" are wrong. We have rubber feet on old Workstations at work which behave the same way. They start becoming viscous like tar. Sadly I don't know when this initially started happening, but colleagues assured me its been going on and a lot of feet are missing entirely because of this (machines are now slightly older than 20 years).

I googled it once, apparently its bacteria eating the rubber.

Natural vulcanised rubber is probably vulnerable to this more than nitril butyl whatever.

Edit: Maybe the anerobic environment inside the tire (at least when this has been going on it probably will be anaerobic) is actually a better environment for this than in open air.

  • Fair enough, but in this case, this seemed to have happened relatively fast. And we would have thought the bacteria would also eat the tire casing. This case was and still is truly a mystery.
    – Weiwen Ng
    Commented Mar 7 at 16:29

looks like it melted. do you live in a hot area? rubber can either melt or lose its elasticity and hardens and cracks. but this just looks like its melted. how long did it go with out being touched? did you use any preventative slimes or puncture protections. my bet is whatever was in it broke down over time and slowly eroded and melted through heat and moisture and tempeture changes.

  • 1
    Hi, welcome to bicycles! If you have follow-up questions for the OP, you should post them as comments, not as an answer that doesn't really provide anything but a random guess. "It broke down" is pretty obvious, and doesn't contribute much if you don't propose a mechanism. You might want to read How to Answer and take the tour.
    – DavidW
    Commented Sep 1, 2022 at 18:44
  • 2
    The melting point of a butyl tube is in the region of 170°C. It's unlikely it melted through heat alone
    – Andy P
    Commented Sep 2, 2022 at 10:05

It's old. Rubber melts. You should replace your rubber every few years, even if you don't ride it.

  • 3
    Apart from when it doesn't and lasts 50+ years
    – Noise
    Commented Jul 1, 2022 at 19:15
  • Yes, there are exceptions to this rule. Would use a 50 year old tire on regular rides?
    – sanjuro
    Commented Jul 1, 2022 at 19:32
  • 9
    The point is that rubber won’t simply melt into a liquid with age.
    – Weiwen Ng
    Commented Jul 1, 2022 at 20:19
  • 3
    I think you underestimate the extent to which this is “melted”. All the repairmen I asked were thinking of something normal. It’s not. It’s literally like viscous glue straight from the glue tube! And it’s sticky like that too. Also, I’ve got a lot of ancient tubes lying around, which go around ropes to protect branches when hanging things from them. All they do, is get brittle, and flake away. Which is matching my experience of what actually happens to old rubber, so …
    – anon
    Commented Jul 2, 2022 at 19:25

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