Bought a used mountain bike for mom. The bike wasn't used in quite a while . Mom used it for 3 weeks , tire pressure was ok but it needed some air. So I pumped air in both the tires to max recommended psi on the tire.

After sometime , both the tires were flat. I did not hear any sound of leaking air right after I pumped it. I tried it again, this time I heard a hissing air leaking sound.

What could have happened ?Not sure if anything in the valve is stuck. How can I determine what is wrong ?

Thanks in advance.

  • 3
    Tubes are consumables - if you have any doubts just replace them.
    – Criggie
    Feb 12, 2018 at 6:26

3 Answers 3


When in doubt, it's much easier to just completely replace the inner tube. They are consumable (like brake pads) and will only cost you a couple of pounds/dollars.

This can be annoying and tricky at first but after a few tries should only take 5-10 minutes or so.

In my opinion, it's easier and quicker to just buy new tubes the next time you're passing a bike shop and spend 15 minutes replacing them than spending several hours identifying and repairing the old tubes - and having the psychological weight of whether or not your repair was fully successful looming over you whenever you ride.

What could have happened ?Not sure if anything in the valve is stuck. How can I determine what is wrong ?

A number of things. The tyre pressure could have been too high for the weight of the person riding it (you don't always need to inflate a tyre to the max pressure), the inner tube could have naturally weakened with age, the rider may have hit a pothole or thorns/nails without remembering it that pierced the tire and tube.

Ultimately; it doesn't matter. The tube is punctured AND old; get a new one and brush it up as bad luck. I doubt reverse engineering the problem at this stage will help you reduce punctures in the future.

  • Thanks for the advice. I have ordered the valves and valve replacement tool online , will give it a try first . If it does not work will have to go for tube replacement option. - Cheers.
    – zennni
    Feb 15, 2018 at 6:20
  • Fair enough. I always recommend tinkering with things just to understand them better, although I wouldn't do this every time. Enjoy!
    – Smeato
    Feb 15, 2018 at 16:06
  • So the new valves arrived. When I removed the old ones, they looked just like new. Anyway I installed the new ones and unfortunately they did not work -(. I tried to change tube many ages ago, it took quite some time , the tire kept coming out of rim and finally when I thought I was done , it turned out that I had ripped the tube inside , maybe because I was not using the right tool. Any YouTube video recommendation sort of like ' bike tube change for dummies' would be great ? thanks
    – zennni
    Feb 18, 2018 at 9:53
  • 1
    The Global Mountain Bike Network GMBN (and sister channel, GCN, for road cycling) are great resources for cyclists. I watch their videos all the time. Both do videos on all sorts of bike maintenance (plus training tips and other advice). Here is the GMBN tyre change video youtube.com/watch?v=qp-3SJK-qkg. GCN have one somewhere as well. Needless to say, tyre levers are an absolute must most for your toolbox.
    – Smeato
    Feb 18, 2018 at 18:08
  • That youtube link was helpful, will give it a try, thank you. Will give it a try.
    – zennni
    Feb 19, 2018 at 0:26

Well, either the valves are not closing properly (may have dirt in them) or there are a punctures in the inner tubes themselves.

You can get the tubes out and test them for leaks by inflating them a bit and submerging them in water, then either patch punctures or remove valve cores and clean out the valves - or - if the tubes are quite old (older than 5 years) you should probably just replace them.


Tires pumped up to max pressure may blow up at the spokes due to a poor rim tape. This does not happen immediately after or during the inflation process but it can take some time to develop. In one of my cases, I heard a blowout and hissing of air at 2 a.m. though I'd pumped them at 10 p.m.

Alternatively, it could be just a regular tire/tube puncture that took some time to develop, and a high pressure helped it to manifest itself. Which is good — now you can fix it at home, not on the road.

Open the tire, get the tube and inspect it. If it blew up at the rim, check the rim tape as well as it will blow up again with another tube if not fixed. If it is just a regular puncture, simply change the tube.

If you do not know how to change a tube in a tire, take your time and follow one of the numerous on-line guides.

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