Wheel widening math? Can anyone help clear this up?

[98 svt]

I have a set of Saleen Lemans wheels that are 18x8.5"
The fronts are +30mm and the backspacing is 5 7/8"
The rears are +10mm and 5 1/8" backspacing I'm thinking of getting the rears widened by 1.5"
I'm wondering if I'd need a spacer in the back, and if so how much? I'm hoping it's minimal, if any.
Anyone that knows how to figure any of this out? I'm a math guy, and this always makes my head hurt when I think about it


Looks like LMR 18x10 Saleen wheels are +22mm and 6.38" backspacing

Am I right in thinking my 8.5s would end up being +10mm and 6 5/8"?

Sounds like the end result would be pretty close to the LMR 10" wheel.

 

[Dusten]

If you add the entire 1.5 to the inside of the wheel the backspacing will be 6-5/8

Offset is dependent on width and backspacing. It will go from 10 to about 22-23

 

[98 svt]

If you add the entire 1.5 to the inside of the wheel the backspacing will be 6-5/8

Offset is dependent on width and backspacing. It will go from 10 to about 22-23

So would that require a spacer? Sounds like it's pretty close to the LMR 18x10 Saleen.

 

[Dusten]

I have no idea. I know dick about wheels on sn95s

 

[98 svt]

I was able to get these pics from a Saleen owner. These are 8.5" rear wheels widened to 10.5" in the pics. I only want to go to 10". Looks like I'll have some room in there.
No spacers needed in the pics below.