I know this question has been asked 1000 times or more I'm gonna try for myself cause surfin this site with 3000 non membes and 50 members is slooooow.
I have a 08 Alpha Off road with key n shackle lift. I have a set of mt baja claws 33x13.5r18 (35's just look too big unless you have full sus. lift)
What is the proper offset and backspacing for the 18's? I found a great deal and the wheels are +12mm. and 5.22"

 

These are the specs for H3 I-5, but I am pretty sure they didn't change the wheels. The websites should help see if it rubs etc...

OEM tires: 265/75-16 (802x265mm). Big Hub.
32 x 10.5 x 16
Bolt OEM tires: 265/75-16 (802x265mm).
Bolt pattern: 6x139.7 (6x5.5).
Offset: +15 to +35 mm.
Tires up to 842x305mm.
Rims up to 26x10.0".
265/75R 16 = 32 X 10.50 X 16
265/70R 17 = 32 X 11.50 X 17
275/70R 17 = 32.50 X 11.00 X 17
285/60R 18 = 32 X 11 X 18


http://www.wheelsmaster.com/rt_specs...text2=Plus%201

http://www.dakota-truck.net/TIRECALC/tirecalc.html