Hey fellas. New to this forum. I was part of another F-150 forum but seems very inactive. I hope this forum is different, lol. Anyway my question is this.

I am looking to get some new rims in the future to go with the tires I just got. I have purchased some Cooper STT Pro tires (295/70/18) to be mounted on my factory rims on my 2014 F150. I looked up the specs of the factory rims and they go as follows.
7.5" wide x 18" with 44mm positive offset. I researched a lot and found I will have no rubbing issues with my current 2.5" leveling kit.

When looking for new rims, I want to make sure I maintain the same backspace but move my offset out a bit. I just want to try to keep the same turning radius. The rims in question have a 20mm positive offset so essentially would push my tires out about an inch. (24mm)
When calculating backspace on my factory rims, I did it by taking the width(7.5) and dividing it in half to get the number with a 0 offset. Then I added 44mm to that giving me 5.48" back space. Is this the correct way to figure out my factory backspace?
With that being said, on my new rims with the 20mm positive offset and the rim being 8.5", would my backspace be 5"?
Got this result by taking half the rim width (4.25") with a 0 offset then adding the 20mm to it, giving me 5.01"
With this smaller backspace, essentially my rim would be about 1/2" closer to the suspension?
I hope I explained it clear enough. Just don't want to buy rims that don't fit properly.
Oh also the centerhub on factory says 86.5mm and the rims I want are 87.1
I'll assume the 1/2mm larger is the proper fit without having to use rings?

 

You have to add 1" to the width to account for the lips of the wheels.

So, for a 18x9 wheel for example, with 20MM positive offset:

9+1=10

10/2 = 5" centerline of the wheel

20mm = 0.8"

5" + 0.8" = 5.8" backspacing

 

That's exactly what I did. Thank you for the confirmation

EDIT. After re reading, I did everything except add the 1".
The stock rim is 7.5". Are you saying I need to calculate like this? (7.5+1)/2+1.732 = 5.982
1.732 is my 44mm positive offset.

So the rim I want is 8.5" with 20mm positive offset
(8.5+1)/2+.787 = 5.537

A difference of .445?

 

You should check out Custom Offsets they have pics and specs of pretty much any setup you could imagine.

 

That site is awesome. Appreciate the hookup.
In case anyone is interested, here is the link
https://www.customwheeloffset.com