Wheel bolt patterns

[Simon Favre <simon@domain.elided>]

All the 101/105/115 series Alfas from the Giulietta through the last of
the US Spiders use the same bolt pattern: 4 x 108mm. The Alfettas were
different. To answer your specific question, the wheels on a 74 Spider
and 74 GTV are interchangeable.

Offset is measured between the mounting flange and the wheel centerline.
The size and offset you can put on a '74 GTV are the subject of some 
debate. ;=) IAP's web site offers wheels in 14x6, 15x6 and 15x7, with
offsets ranging from 15mm to 25mm: 

http://www.international-auto.com/j_home.html (You can download PDF files)

The following info on offset is from the Tire Rack web site:

http://www.tirerack.com/wheels/wheels.htm

Zero Offset
 The hub mounting surface is even with the
 centerline of the wheel. 

Positive
 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 and newer rear drive
 cars. 

Negative
 The hub mounting surface is toward the
 back or brake side of the wheels
 centerline. "Deep dish" wheels are typically
 a negative offset. 

George Hovis wrote:

>Can someone give a quick run-down on wheel bolt patterns and which wheels 
>are interchangeable.  I have a '74 GTV and a set of stock alloy wheels off 
>of a '77 Alfetta which I understand to be a different pattern.  Are the 
>wheels for the '74 GTV interchangeable with a '74 Spider, for example?  Is 
>the '74 pattern 4 x 108? 4 x 98?  4 x 100?  4 x something else?  If looking 
>to aftermarket wheels, what else does one need to know?  (Such as off-set, 
>what's that?)

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