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I put some extra air in my rear mountain bike tyre yesterday. It uses the SLIME inner tube. It wasn't flat nor had a puncture, I was just topping it up to make the tyre a bit harder.

I cycled to work on it and all was fine. When I came out of work however, the rear tyre was completely flat. It was absolutely fine when I got to work though.

It appears that since opening the valve to pump in some air, it's been slowly leaking back out of this valve. It wasn't a problem until I did this. It's a schrader valve if of any use/relevance.

Is there anything I can do? I pump the tyre up and it just deflates again through the SLIME inner tube valve (which has spat out a bit of it's green gunk incidentally). Just seems like a complete waste of money at £16 per inner tube if it just leaks via the valve (regardless of whether it's going to seal any punctures or not).

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FWIW I've tried slime tubes more than once and I have come to the conclusion that they are indeed a waste of money (and super messy to boot.) –  WTHarper Sep 12 '13 at 12:52
    
I've yet to really test whether it does the job they're meant to by sealing any punctures. I've yet to take the inner tube out since they've been installed. (I've literally just got one for my road bike as well so that's not music to my ears) :( –  zigojacko Sep 12 '13 at 12:59
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Virtually all Schrader tubes allow you to remove the inner "core". You can get a "valve core" tool (some valve caps have the tool built in) at any auto parts place. Remove the valve core, clean, and reinstall. (Probably you should do this while the valve is at the 3/9 o'clock position to minimize Slime leakage while the valve is out.) Or it may simply be that the core is loose. –  Daniel R Hicks Sep 12 '13 at 14:54

2 Answers 2

You might want to remove your schrader valve's stem (innards) with a stem removal tool and check the valve's rubber seat, located on the part that you remove. There may be debris lodged in the valve seat such as grit or sand or some dried slime that would cause it not to seat and seal properly. Also consider switching the valve stem core from another valve from say an old inner tube and see if that does the trick. Unless the valve was damaged or the old tube you take it from is real old, the valve stem core will usually last much longer than the actual tube. Many years ago when my bike had schraders, I'd keep a couple of valve cores from old tubes in my patch kit in case I experienced a valve problem when out on a trek.

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Just to clarify terminology a bit: the valve stem is the tubular part that goes through the hole in the rim. The stem is not removable, it is fixed to the inner rubber tube, the core is the removable part. All schraders have removable cores. Some prestas have, and an older style of valve, the dunlop, has a core that is removable by hand (no need for tools) –  Jahaziel Sep 13 '13 at 3:05

Some Schrader valves have removable innards. There are even special tools for them, also a small pliers might do. Maybe yours has gotten loose and is now leaking. Check whether the pin in the center of the valve is "hidden inside" the valve itself. If not, that's a very likely culprit.

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I did check this and the valve pin appeared to be just inside the flush of the valve ridge (which I would presume is about right)? I will check this out again though - thanks. –  zigojacko Sep 12 '13 at 12:57
    
Even so it could be a little lose, especially since the green gunk is leaking out. –  arne Sep 12 '13 at 13:01

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