Locating what’s causing my flat

Hi all from Pittsburgh where there’s no longer chance I frost at night and we’re not on lock down but still can’t go to restaurant or salon.

I’m struggling on what I thought would be straightforward

bike’s got a flat

so I took out the tube, filled it a bit and put it under water

found a leak and patched it
Did not find any protrusion in the tire by using the “ run your finger along the inside”

put back in

goes flat after week

take tube out again and put under water but can find no more leaks and no protrusion in the inner tire

so is there a better way to check a tube for leaks

And a better way to check tire for puncture points

otherwise I guess I’ll replace the tire and the tube

thanks !


Legendary Member
Are you able to turn the tyre inside out?
Anything in the tyre has a better chance of showing through on the inside.

Any damage to the valve, where it meets the rim? Any blockage in the valve?


1:- Run a bit of cotton wool around the inside of the tyre. It may snag on a very small point that you didn't feel.
2:- Go around the outside of the tyre looking for small cuts. If you find one then pinch the tyre to open it up and check there's nothing in it. If there is then you need to pick it out.
3:- With a very slow puncture it can be helpful to put a lot of air in the inner tube to help find the hole. I use roughly double the diameter as a good guide. Also double check it's not leaking out of the valve.
4:- When you put the tyre back on, line a mark on the tyre with the valve. This way when you next puncture you can use the distance between the valve and the hole in the inner tube to measure between the mark on the tyre and what probably caused the puncture. It does make finding the cause easier.

Luck .......... ^_^
Also, if you have a puncture whilst out and about, take one side of the tyre off, try not to let it move, leave the tube in, attached by the valve, then re inflate the tube, and work your way round until you locate the hole. If the tyre hasn’t moved, you then know exactly where the issue causing the puncture is, even if it’s dark. You can use a bit of the content of your drinks bottle to help find the hole if needs be as well. It could be an issue with the rim / rim tape / spoke holes / spokes too, not always the tube / tyre / pointy object.


With a very slow punctures and using the bowl of water method to find the hole, you'll only see a very tiny single air bubble escape every few seconds. So go round the tube very slowly and make sure the water is still as you check each section. Pull and stretch the tube in all directions as well as you go round. Examine very carefully the area you have already patched. Sometimes it doesn't seal fully, but just enough to keep air in when under the water.

Good luck


Über Member
When checking put the valve under water as well, sometimes they leak!

Good luck!

Ajax Bay

East Devon
All the above.
Eliminate patch failure cause by replacing with new tube.
Consider where on the tube the puncture was. If on the inside of the toroid then very likely this is a spoke hole edge issue - and that has been exposed by the rimtape slipping sideways at that point. You'll only discover this by taking the tyre off completely and checking the rimtape.
Solution: remove the rim tape; with a bit of emery paper remove any rough edges of any of the spoke holes and the valve hole; order some replacement rim tape; refit current rim tape so you can ride; replace rim tape at early opportunity; replace rim tape in the other wheel too.
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If you'd marked the tyre at the valve before taking the second tube out then identified the puncture, you could have checked the tube against the tyre for the possible cause. That way you would at least be looking in close to the right place (unless of course it was caused by a spoke).
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Grumpy Old Barstool
Oop North (ish)
it's a elimination process,

Tube goes down, patch tube
Tube goes down, new tube
Tube goes down, new tube, new tyre
Tube goes down, new tube, new tyre, new wheel
Tube goes down, new tube, new tyre, new wheel, new bike,
Tube goes down, new tube, new tyre, new wheel, new bike, new hobby
Hope that helps :laugh:
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