wheel offset v.s. backspacing. Same?

okay, sorry to always ask questions but I need some help on this. Bruce Andersons book on pg 215 tells me that the offset of my 16X7 fuchs is 23.3 mm. If I take the wheel off and measure the distance from the mounting surface to a straight edge layed across the inner side of the rim I get 125 mm, which is what the performance catalog pg 64 tells me I should measure. What is the difference?

------------------
85 Carrera Targa

Please recalculate:

Offset and backspacing are two different measurements which give you the same information. If a rim is 8" wide, the centerline is at 4". Offset is the distance from the centerline of the rim to the back of the mounting pad of the wheel ie where the back of the wheel touches the hub of the car. Offset can be positive or negative depending on whether the back surface of the mounting pad is offcenter towards the outside of the wheel or the inside.

If you laid the wheel face down on the ground, and laid a straightedge across the back lip of the wheel and measured down to the back of the mounting pad, that is backspacing. Did I confuse you--its hard to put into words, easy to see in a drawing.

orb, terry,
THANK YOU.

------------------
85 Carrera Targa