I flatted the front wheel going up a climb the other day - I heard the pop and the PSSSSHH, and I could see a geyser of pale "steam" or vapour coming out the puncture.

I swapped out the tube for the spare and continued, but noticed the tube was wet inside the tyre. It hasn't rained on my bike for months.

When I got home I patched the tube, and noticed a lot of dampness around the hole. When inflated it bubbled like a mud pool. The tube also felt squishy and I couldn't push all the air out when stowing it later.

I guessed there was some water inside, so the tube was left hung up with the presta valve at the bottom and unwound.

8 hours later this is what it looked like underneath: 8-hours-later

Bigger photo of the pool - this is 10 hours of draining time: Quantity is about 5-6 dessert-spoons full (estimated) More tyre blood

The liquid was runny not viscous, and was clearer on top with the colour sunk to the bottom. The coloured bit looks like mud, or a suspended powder

The tube is labelled as "CST 700c 19-23" and a long number There is no mention of any sealant or puncture resistance to this tube.

Why does my tube have brown liquid in it?

EDIT: I removed the valve core and tried to purge the goop using a rolling motion. It didn't work so I junked the tube. I cut it open to see what was blocking the open valve, and it looked like this:

Not the best photo sorry, but its a jelly-like mass with many black dots like grains of sand. I suspect these are suspended fragments of butyl rubber from the inside of the tube. enter image description here

TL;DR? Squishy tubes are bad - buy a new one.

  • Possibly related to bicycles.stackexchange.com/questions/8010/… but that references a white liquid.
    – Criggie
    Commented Dec 8, 2015 at 8:46
  • 1
    Yep, that's plain old rusty water. The air compressor you used to fill the tire was improperly maintained, and water had accumulated in the air tank to the point where it was overflowing. Some of this water blew into the tire when you filled it. Air compressor tanks must be drained at regular intervals to prevent this. Commented Dec 8, 2015 at 20:49
  • @DanielRHicks Yes, I use a floor pump which was bought new because I got this road bike. Or a 40+ year old frame pump if I'm riding. I have no idea what the previous owner used but a compressor makes sense. Scarey thing PO worked at an aircraft workshop and I hope they didn't do the same to aircraft tyres!
    – Criggie
    Commented Dec 8, 2015 at 20:56
  • All I know is I wouldn't get anywhere near that compressor. Water has been in that tank a long time and it's rusting it from the interior. I wouldn't want to be anywhere nearby when the tank fails. Commented Jul 24, 2016 at 4:41
  • @CareyGregory agreed that would be bad. In this case, that was a proper CST brand tube with their brand of sealant pre-installed.
    – Criggie
    Commented Jul 24, 2016 at 5:37

2 Answers 2


I've seen that color before. If you are filling from a compressed air tank, make sure the tank has been bled recently. More frequently in humid areas air tanks will get condensation inside. Normal maintenance is to bled the water out of the tank. The condensation rusts the inside of the tank and can eventually cause tank failure. When you put an air line on them the air comes out but a little vaporized water goes too. That gets in your tubes and builds up over time if you use the same filling source. Avoid by placing an in-line filter on your air hoses as well. Test by blowing air over your hand from a safe distance. If it's wet or damp you have found the culprit.

Experience case: They didn't bleed the compressor at the beach shop I worked at. I bled it when we upgraded to prep it for storage. One gallon of water came out of that little six gallon tank. One-sixth of the volume for air was taken up by the water and it was the cloudy brown milky color too.

Also, respectfully agreed. White liquid is often stop flat liquid filled into a tube as a flat preventative. Stop flat can be neon green in color too.

  • 3
    Yeah, that clolur looks familiar from bleeding my old central heating system!
    – PeteH
    Commented Dec 8, 2015 at 10:09
  • 1
    Yep that looks like rust in water. Also something you might see coming out of the tubing of your bike if you're unlucky :( Commented Dec 8, 2015 at 12:00
  • 1
    A related thought: someone about to sell you a bike they weren't riding might have left their pump outside and pumped rusty water into the tyre when pumping it up to sell. It's amazing what people do when selling bikes. I bought one with a 24" tube on a 26" wheel. How they got it on I've no idea but it held. Admittedly that was a very cheap bike.
    – Chris H
    Commented Dec 8, 2015 at 19:58
  • 1
    @ChrisH - It would be very unusual for a hand pump to accumulate enough water in it to produce this problem. The pump would rust up and freeze pretty quickly if allowed to get that wet. Commented Dec 8, 2015 at 20:52
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    @DanielRHicks I can't disagree with that, it just seems marginally more likely than the alternative. With the moving parts of a pump being rubber on steel for the cylinder, and often a steel shaft in a plastic cap, it could probably be quite rusty and still pump, but getting that much water in does seem unlikely.
    – Chris H
    Commented Dec 8, 2015 at 22:08

I spoke with the bike's previous owner, and he confirmed that the tyre was never filled from a compressor, always used a floor pump or a minipump which takes air from the atmosphere, so little chance that water went in via the pump.

The tube was a self-sealing CST tube, worth around double the cost of a normal tube. The brown poop liquid IS the sealant liquid in this brand of tube. It was no more than a couple months old as well, fitted to sell the bike.

I'd guess self sealing road tubes are a bit useless based on this.

Accepting this answer because it came from the previous owner.

  • Maybe the self-sealing tube had been badly stored and/or had been kept on the shelf for too long. Tyre sealants have a (long) finite lifetime. When it failed, were you riding in unusual temperatures? Presumably there's a temperature range over which they work. It's also possible that the puncture was too big to seal before the high tyre pressure pushed quite a lot of sealant out.
    – Chris H
    Commented Dec 24, 2015 at 9:27
  • @chrish Good point - Even though the tube was freshly installed, it may have been on the shop shelf for years. I never saw what caused the puncture, but it was not a hot hot day, maybe 25 degrees C air temp, and a 12-14% climb angle, and a tailwind up the hill.
    – Criggie
    Commented Dec 24, 2015 at 9:53
  • 1
    If puncture resistant tires are an option, that's way better than any sealing fluid in the tube. At the very least, a fluid filled tube will be loosing some sealant after the puncture, and you cannot patch these tires as the sealant has the habit of unglueing the patches (at least that's my experience). So it's basically: Use the sealant filled tube until some punctures have accumulated and you get a flat tire anyway, replace the tube and repeat. A puncture resistant tire gives you much longer intervals between the punctures, and thus requires much, much less maintenance. Commented Jul 11, 2018 at 18:19
  • 1
    self sealing tubes have a pretty poor reputation. I've seen a 'slime' branded one leak a massive puddle of goop all over everywhere whilst failing to seal a small hole. Whereas in mountain biking tubeless tyres/sealant is very reliable and usually seals holes instantly.
    – Andy P
    Commented Jul 12, 2018 at 9:23

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