So I came out of work to find a flat tire. I pumped it up and found the leak is coming from the valve stem in full force. I replaced the core, hoping that was it, only to find out that it is coming from the rim where the nut is holding the valve stem in place. There is rust at the base of the nut, and rust just above the nut on the stem. (I am assuming from the moisture from the air coming out.) Is this fixable? or does this mean I need a new rim? (I have read some people say they have a small leak there, and they put a washer on, cut a metal valve cap and used it as a nut). But that sounds a little sketchy for me, since this leak makes my tire go from full to flat just as fast as if I had removed the valve core.