Originally Posted by djpathfinder

Look at the back side of the wheel. The wheel specs should be stamp on the back. You'll see "18x8" somewhere. Then you should see either "ET" or "+" (or something like that) followed by 2 numbers (eg ET 30), which tells you (+30 mm) offset.

Like Semtex said you could still use the tires so long as overall diameter is around OEM spec (25.6", IIRC).