Exactly how much deviation can you have with tire size?

[BATMANs]

before the TCS or ABS starts to freak out?

I like the run 215/40/17 in the front and 275 or 285 35 or 40 series on 18" wheels in the back.

If anyone knows the % deviation I can plug it in this formula:

http://rx7.org/public/tiresize.shtml