What's offset, and what fits?

[SilverGlow]

I figured this was newb enough to ask here: what exactly is the offset measure on rims, and what range will fit on our car (for 17s)? Right now i'm checkin out 40 mm...

[celiboy07]

40 no problem. I say stay between 30 and 42. The lower the offset, the further it pushes the wheel out. The higher, the closer inside to the wheel well it will push it in.