I'm looking to buy some new tires for my ride and am wondering about rubbing issues, I have 265/35/18 in the rear already, they dont rub at all, however Im not sure of what the offset of the wheel I have is, and dont know how to tell, being that I bought em off someone else....so it looks like the falken 615's arent sold in a 265 size, only a 275/35/18, anyone know how fitment would be in the rear with this size?

You can get 275/35/18 with a 45-50 offset and a 9.5in wheel:

http://www.flickr.com/photos/tevaburns/sets/72157594463515029/

http://farm1.static.flickr.com/224/507084149_84f06b3b07.jpg

is there a way to find out the offset by looking at the wheel?

It's stamped on the wheel.

you could always measure the distance from the inside edge of the wheel

place a piece of wood across the back of the wheel and then put a ruler vertically in the middle touching the center section. If the wheel is 9.5" wide the overall width will be 10.5" so if a wheel has 0 offset your measurement will end up being 5.25"

you can use this measurement to determine the wheel's offset