ET question

with an ET of 40
Is "ET" backspacing? Is that in mm?

Post some photos and part numbers of what you are looking at and have now.

Did some digging..

ET is german term for backspacing

"Offset is usually stamped or engraved into the wheel and is measured in millimetres of 'ET' [ET is the short form of the German word 'Einpresstiefe' which literally translates as 'insertion depth'] Positive Offset wheels have their mounting face toward the front face of the wheel"


offset-en-min.png

So yes if you go from +40 to -9 you would be moving the centerline of the wheel 49mm outword. (About 2 inches)