My advice is to stop, put the tools down, see what other ideas people come up with, but don't touch anything until at least tomorrow when you've had time to think and weigh your options. You may not be beyond help, but one more mistake and you could be. With that said:
I guess you could tap it one or two sizes larger, but you may have to drill the disc brake mount hole slightly larger to accomodate the lager bolt. This would work, but may weaken the brake mount so don't do it, just think about it for now.
I also thought of another option which would be to install a longer bolt of the same size backed with nut. This shouldn't hurt anything if it all fits together and is probably a better option.
Another option which may work is to use a heli-coil which is basically a threaded coil that you screw in and I think cement into place after drilling and tapping out the hole larger. I've never been in so deep as to actually use one though.
And as I'm sure you now know aluminum is soft. When in doubt just use blue locktite, then snug is plenty tight.
Last edited by biknbrian; 01-12-08 at 01:53 PM.