It seems that some wheel companies like to keep the offset as a proprietary part of their wheel builds. They each have their own fit based on their own measurements. The last build sheet I received made no reference to offset.
I guess so. This is the 4th or 5th time I have asked this question on wheel threads. :confused
This is openly discussed on non FGT forums.
I could understand keeping a particular alloy secret but I would have to believe the owner would be told the backspace if he asked. Ford prints the Optional BBS backspace figures in the SVO catalog. For a 19" x 13" with a 335 Bridgestone, 1/2" added to the inside and 1" added to the outside works but that increases the torque on the suspension. I don't know if 3/4" to the inside and 3/4" to the outside clears the suspension.
For the Front, an 18" x 10" and a 265 Bridgestone adding 1/2" on the inside and outside works (clears everything) and keeps the suspension load the same.
I had HREs made for my Z8 10 years ago and they had the backspace data on the build sheets.
Sure would like to know how it flies on the 20" diameter wheels and tires.