How to measure backspacing (ie what do i have)?

[robhurlburt]

Noob question here, just trying to learn:

So i found this online:
The easiest way to measure backspace is to lay the wheel face down onto the ground so the backside of the wheel is facing up. Take a straight edge and lay it diagonally across the inboard flange of the wheel. Take a tape measure and measure the distance from where the straight edge contacts the inboard flange to the hub mounting pad of the wheel. This measurement is backspace. The above photo shows three wheels with 2",3", & 4" backspace.

And this diagram:

Is the inboard flange the TOP of the lip, or is it the first bend? My gut is telling me its the top lip, but I want to be sure before i order another rim

Do I have 4in (top of lip):

Or 3.75in (sitting on flange):

 

[Ronbo]

Where it says 'Rear Spacing' is what you want.

 

[robhurlburt]

Where it says 'Rear Spacing' is what you want.

thanks ronbo! then i have 4in backspacing.