Go Here:
http://www.yokohamatire.com/utcustom.asp
and it has a useful explanation of offset and pictures to maybe make it clearer.
My only beef is that, I had a 17x7inch 6 spoke infiniti wheel from my friend, which im guessing is off of a 03-04 g35 sedan because the g35 coupes dont havem. i looked up the specs on it and it is +40mm. g35 coupe (which i own) is +30mm in front, +33mm in rear. I tried to install it and it did not sit flush on the hub. well i tightened the crap outta it, went and ran it and the nuts came loose! bad!!!!
so then i took it off, put my stock rim on it.
just no one wants to take a stab at my question, because no one wants to go smaller in the front, everyone wants wider. and plus i dont think anyone has ever done it before. just wondering.
i noticed the bolts don't go through the holes fully as they do on my stock rim. that's probably why the nuts came loose after driving.