QUOTE(Aaron Cox @ Mar 26 2007, 07:50 PM)
let me interject a little. offset is
a pretty useless number, as it varies by width....
Backspacing
is constant. backspacing is from the inner lip of the wheel to the
mounting face. on a 914, you want between 112-120mm backspacing.
every
fuch wheel has almost the same backspacing even though the width
changes. pretty cool.
so if you know the max back spacing you can
run on your car (before wheel hits inner fender well) You can then pick
a custom wheel to fit your car in ANY width you would like.
just
easier to calculate IMO,
those look so sick on your car
gint!
Actually, I disagree.
Offset in it's simplest form is the distance from the wheel's
centerline to the hub mating surface regardless of the wheel's width.
And I like to have all of the numbers. I have no issue with calculating
the offset in order to know what I'm dealing with. But that's just
me...
Details:
Factory 5.5" 4x130 Fuchs wheel
- Overall
wheel width - 6.250"
- Wheel width (between the inner beads) 5.5"
- Backspace
4.6875"
- Offset 1.5625"+ (39.6mm)
Performance Superlite
15x7 4x130 wheel
- Overall width 8"
- Wheel width (between
the inner beads) 7"
- Backspace 5"
- Offset 1"+ (25.4mm)
Edit:
I
cheesed the Fuchs measurements. They have been corrected 3/28/07.
Factory 4 lug (4x130 bolt pattern) Fuchs wheel has an positive offset of
39.6mm.
Good information about wheel backspace
and offset from Yokohama's web siteQUOTE
High
Performance Wheels
The following are various high performance wheel
measurements that play an important role in determining tire and wheel
fitment:
Wheel Backspace
This is the distance from the back
edge of the wheel to the hub mounting surface. To determine the wheel
backspace:
1. Position the wheel face down.
2. Lay a
straight-edge across the back of the wheel. Measure the distance from
the straight-edge to the wheel's hub mounting surface.
Wheel
Offset
The wheel's offset is the distance from its hub mounting
surface to the centerline of the wheel. The offset of a wheel can be one
of three settings:
* Zero offset: The hub mounting surface
is even with the centerline of the wheel.
* Positive offset: The
hub mounting surface is toward the front or wheel side of the wheel.
Positive offset wheels are generally found on front-wheel drive cars.
* Negative offset: The hub mounting surface is toward the back or
brake side of the wheel's centerline. "Deep dish" wheels are typically
negative offset. Offset can be calculated by positioning the wheel on a
flat surface and measuring its overall width and backspace as shown
below. Divide the overall width by two, then subtract this result from
the backspace value.
Offset = Backspace - (Rim Width ÷ 2)
Click
to view attachment
Here's a
drawing from Fikse that I especially like.QUOTE