I have been having trouble the last couple months with one of my
(new) Mickey Vs going completely flat over a period of 2-3 weeks.
It fills right back up though upon inflation.
I finally took the car back to the discount tire place where I
bought the tires and had them take it off and inspect it.
It turns out that the chrome (I have the after-market chromed
wheels) around the rim of the wheel where the tire bead sits had
some bubbling and flaking. 
This caused the bead not to stay
sealed against the wheel rim. The tech scraped off the loose
chrome in that area, applies some sealant, and re-mounted the
tire.
So far, no more leak! :)–
&:-)) Paul '88 XJ6 VP (and '90 XJS HE on way)
Garland, Texas, United States
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