Tyre suddenly leaks air at valve. HELP!

Last night I decided to increase the pressure in the tyre a little bit,
so I clamped the pump on and the pumps' own pressure gauge read 37psi as
I expected. I pumped expected to get a target of around 50psi, but once
it got to just about 42psi there was a sudden hissing of air, and within
seconds my tyre had gone completely flat!

I checked the pump was clamped on firmly and pumped it up again from
scratch, and again, and again, and then realised that the valve itself
is leaking. All attempts to reinflate the tyre have been disastrously
unsuccessful, since as soon as the pump is removed all the air escapes
through the valve within seconds.

If I push the valve partially into the tyre while pumping, it will hold
up to about 20psi before starting to leak slowly. Of course as soon as I
release the pressure (i.e. take the pump off) all that air escapes
again.

It is not a tyre puncture, since I can actually feel the air escaping
from the valve itself and the air escapes *in seconds*. The uni has only
ever been ridden indoors,

It is not a fault with the pump, since the valve hissing continues even
*after* I have removed the pump from the valve.

It is a 20x1.95 Maxxis Hookworm tyre that is rated up to 110psi, with a
(leaking) Schrader valve.

So what could it be? And more importantly can I do anything about it? Is
my one month old unicycle already damaged? I can't bear to be without
it!


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gkmac - Shy Nervous Newbie
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