Usually, it is written IS and a number or ET and a number.
According to my catalogue...
Regular 530i has +20 offset, 8" wide wheels.
M5 has +45 offset in front and +25 offset in rear, 8" wide in the front, 9" wide in the rear.
And offset is relative to the width of the wheel.
But for winter, you don't have to run staggered.
Last edited by crxgsr; 08-29-2010 at 10:35 AM.