The back of one of the wheels in my garage has "ET20" stamped on the inside of the wheel. I assume this is the offset?

But, what does it imply? Millimeters? Positive offset or what?

Thanx, folks ... appreciate your help.

 

20 millimeters from the center line.

My guess is negative (or towards the outside of the wheel).

 

offset is the measurement between the middle of the wheel from a perpendicular line, to the point where
the wheel touches the hub.
Yes it is inversly proportional.
In other words, the higher the offset in mm, the deeper the wheel is going to mount in the wheel well.
In a carrera S, 4S, or turbo body, the offset is 40 mm.
If you mount a narrow body turbo twist wheel with an offset of 65 mm, the wheel will sit 25mm inside. (and the tyre size is the same in this example)
So there will be a lack of 25 mm.
hope my answer was not as complicated as it sounds

 

 

hi you gotta love this place there is an answer for every question

 

Yeah .... you are correct. I love this place!

Thanx for the answer to my question, guys. Great explanation of offset and what it all means.

Cheer ... and happy T'sgiving, too.

 

+1 and usually pretty timely too.

Mahalo Kelly... for the diagram.

 

correct

It is the distance in mm from the plane of the middle of the wheel to the mounting face.



Almost all Porsche 911/964/993 wheels use a + o/s

negative o/s was used on the '60s US muscle car wheels, it gives the deep dish look.

here is a +10.6mm 8, note the almost flush lug holes


Here is the same wheel w/ +23.3mm ET, note the sunken lug holes because the center section is moved out board 12.7mm


and a +57 8