Originally Posted by HondaKiller

If its not the valve stem, and it passes a water test, then your rim is bent. A bent rim can cause an undetectable slow leak. They have this red goo they can line the tire with when they put it on rim that will stop the slow leak from a tweaked/bent rim. It's nasty stuff though, once you put it on its nasty getting it off the rim when its time for new tires. I would suggest buying a new rim if that is the case.