On some TV show (can't remember which one) they tried what presure can a regular car tyre handle. At 15bar the alloy failed, but not the tyre.
I have once inflated a golf 3 tyre to 6 bar and left it overnight (not on the vehicle of course), because it didn't want to mount itself properly in a nice way. I didn't care for the tyre or the rim, if it'd have exploded, it would have been funny.