Wheel Offset / Track Width Adjustment

Hello, rim size 7.5 x 17 inches, offset 35 mm, widened by 20 mm.
Was wäre die richtige Größe ohne Verbreiterung so es die gibt? ET 55 or 15?
When the rim is flush with the edge of the fender.
It's measured from the center of the rim to the mounting surface, so without wheel spacers, the offset would have to move 20 mm further inward, resulting in an offset of 15 mm.
Can anyone confirm this?

http://de.wikipedia.org/wiki/Einpresstiefe

Positive ET essentially refers to a narrower track width, while negative ET indicates a wider track width. An ET of 0 means that the center of the tire is precisely aligned with the mounting surface on the brake disc or drum.

teileklaus wrote:

so, ET 15 mm?

Okay!
If something is attached to the rim, it means the offset is smaller.
If something protrudes from the rim, the offset is larger.