I’m trying to get an old bike I had in storage up to riding condition. I’ve washed it and there is no foul odor from the bike normally, however when I pump the back tire, the air leak smells really pungent. This is not a problem for the front wheel.

Do you think something could have gotten inside the tire? Is there anything I can do to get rid of the smell without buying a new one?

  • 2
    Pungent chemical? If so, what, like solvents/petrol? Ammonia? Rubber? Dead animal?
    – Chris H
    Jul 5 at 18:09
  • 2
    I would describe it as closer to dead/rotten smell or perhaps akin to fecal matter. It is not noticeable at all in normal operation, but when I attach/detach a bike pump the slight air that leaks is quite strong
    – guest12445
    Jul 5 at 18:18
  • Something got inside the tire: extremely unlikely, the valve may leak air, but to get in substantial volumes and have some form of life inside you need something in liquid form (water with "dirty", for example) and this cannot really go through the valve. The air from some tubes simply smells more than others.
    – EarlGrey
    Jul 8 at 11:18

5 Answers 5


In my experience, the inside of inner tubes always smells bad, so there's a chance that while in storage, the air inside the inner tube has gone particularly pungent and will dissipate after use. I often cut punctured tubes into strips to use as rubber bands so I'm very familiar with the smell!

I would describe the smell as fishy, and I've come across the notion that fish bone meal is used to powder the insides of inner tubes, though that appears to be false based on this article where the author contacted inner tube manufacturers to ask about the smell: https://www.bikeradar.com/qa/revealed-why-inner-tubes-smell-of-fish/

  • 4
    +1 for mentioning the fish smell out of perfectly usable inner tubes. It happens on bicycles with 20 year old inner tubes, and it happens to my most ridden and most well kept for bicycles that had their last tube change less than a year ago.
    – jayded-bee
    Jul 6 at 10:57
  • 4
    "Trimethylamine, which has a strong fishy smell, was found in both rubbers for the first time. It probably originates from the anaerobic reduction of trimethylamine N-oxide and is another strong contributor to the overall odour." "result of enzymatic and microbial degradation as well as thermal effects." analyticalscience.wiley.com/do/10.1002/sepspec.1414134e183 See also, Volatile Organic Compound and offgassing.
    – Mazura
    Jul 7 at 0:49
  • 2
    It's funny to me, I have never related the inner tube smell to fish. I'm used to recicle inner tuber for many purposes but any time I cut one open I only perceive the smell of talcum and the same smell that has the air coming out of any tire (including car's) or even compressor tank. I don't mean to contradict, just point out that either some people are not sensitive to the chemical in question or not all "butyl" tubes are actually made of the same materials.
    – Jahaziel
    Jul 7 at 14:15

In my experience, rubber or rubber like components of a bike are better changed when bringing an "old" bike back to use condition.

Inner tubes degrade and become porous and prone to "spontaneous" puncture. Rim brake pads become hard or brittle and do not stop the bike adequately. Both of these are a safety concern.

I know this is subjective, but in my opinion, it is better to replace the tubes as they are cheap in most places. In any case, it is worth dismounting the tires and inspecting the inner, the tube and the rim tape, and make sure there are no foreign objects or anything that can cause a puncture.

Brake pads, on the other hand, are definitively not the part to skimp on (in case you have old ones still on the bike - and yes, I'm assuming you have rim brakes; I have never had an issue with disk brake pads due to age alone).

-- End of answer and beginning of anecdote --

I learned about those in an event where fortunately there was no consequence for me other than a scare.

I decided to ride a very old road bike down a steep and long road. I had tested the brakes on the flat and they seemed okay. The tubes held air just fine so I thought there was no high risk.

Turns out the dried brake pads had almost no power when in the downward slope and I had to squeeze the levers hard and continuously just in order to avoid overspeed, In fact, I could not bring the bike to a stop. Near the bottom of the hill, both tubes "exploded" due to rim heating (I guess). They both produced a "bang" sound similar to small fire crackers losing all air instantaneously.

Luckily they did not burst at the exact same time but one after the other and over a straight stretch of road, and also, there was very little traffic on that road at that particular time. I managed to keep control and could stop as I reached a level part of the road. I touched the rims and they where hot enough that I could not keep my fingers against them for long. When I got to evaluate the tubes they both had long gashes.

Another comment:

Tires are somewhat more forgiving and also can be more easily inspected, but they also become harder and thus they lose traction more easily. In the case of flat handlebars, grips may become also hard and thus less comfortable to use, or the opposite, they become a sticky goo, but, unless they are slipping off the handlebar, they aren't much of a safety concern.

Bottom line: If you are on a tight budget it is understandable to try and keep as much of the bike as possible, but seek to replace critical items as soon as possible as an accident can easily result in way more expense. If the bike is going to have commuter use, then a puncture or tube failure can result in being late for an appointment.


The easiest solution would be to replace the inner tube. If you'd like to avoid that cost and waste, it may be possible to squirt some liquid disinfectant inside the tube by first removing the valve core. I wouldn't recommend bleach because the chlorine might attack the rubber, and rubbing alcohol probably isn't a good idea for the same reason (as well as the fire/explosion hazard). Household disinfectant/cleaning spray would be a good choice.

Does that bike have tubeless tires or sealant-filled inner tubes by any chance? Tire sealant can sometimes rot and smell terrible. Perhaps the front wheel's sealant dried out before it could start rotting.

  • 3
    Even tubes can have sealant in - I've found a pre-slimed free on a bike I bought 2nd hand. It didn't seal the big gash but was unpleasant to handle
    – Chris H
    Jul 6 at 7:12
  • 2
    @ChrisH Thank you, edited that in.
    – MaplePanda
    Jul 7 at 15:17

I don't have an answer directly, but if I were in your position I'd take the wheel off the bike, take it outside.

Then I'd remove the tyre from the rim, the tube, and look at the rim strip too.

One of those is likely damaged in some way, or there's another source of the smell like a dead mouse. It could also be animal urine sprayed on the bike while parked though washing should have minimised that.

Last resort is to change the tube to a new one, and perhaps cut open the old one for inspection. I wonder if there was an organic-based sealant in the tube and it has rotted ?

Good luck!


Any bike left for some years will have stinking air in the tubes. It would be the exception if mold does not build up inside. The mistake is to inhale that air, or to let the air out indoors.

While pumping we insert humidity into the tube. Mold or other micro-organisms will almost surely build up slowly inside. Take a clear glass bottle; fill it with a drop of water; seal it for five years (in a dark place); then check how the glass looks like on the inside. That is what would also be inside the tires, except that if it's black mold, it will be less visible on the dark background (if you decide to slice it to inspect it).

If the rubber remains supple, there is no reason to change the tube, and it is not a health hazard as long as whatever is inside remains inside.

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