I need help with tire size

I saw something a number of post back and I need to correct it. Most wheels are this backspace , unless they are custom.
15 x 7 = 4.25 backspace
15 x 6.5 = 4.25 backspace
This is a factory ralley wheel and it may apply to a steel wheel , I didn't measure those today.
This is why a 15 x 7 ralley wheel trim ring will not fit a 15 x 6.5 ralley wheel. The 1/2 inch difference
is all on the front side of the wheel. I got them off the shelf and measured them today , just to be sure.

Frank