Gazim:
Your "source" is correct, the distance from the mounting surface to the center of the wheel is referred to as "offset". Backspacing and offset are related but seldom the same. When you are measuring to see if something is gonna rub, backspacing is usually the number to use. Don't forget there is about 1" of tire bulge also.
BigChevy3600:
From the mounting surface to the centerline of wheel is referred to as "offset". Tires do not have backspace, "wheels" have backspace. ;-)
Ghostrider:
The link you provided refers to "offset", not backspacing. :-)
Gazim wanted to know how to measure "backspacing". :-)
hotshoe36:
You are correct! Remember that "offset" could be a negetive number. It usually is not, but could be. "Offset sometimes is 0 (zero) which means the mounting surface is exactly in the middle of the wheel.
Finally Gazim,
Sorry I am being so long winded. To measure backspacing, lay the rim (without tire) on the floor or table and lay a straight stick across the backside of the rim and measure down to the mounting surface. Wallah, backspacing. This number plus 1" for tire bulge plus another 1" is what will be needed to keep the tire from rubbing the frame. Ask me how I know. Remember If the WHEEL is too wide the front side could rub on the outer fenders, not usually a problem but somethin to consider if the wheels are much wider than about 8 inches. Also, I am speaking in generalites here, not all vehicles were created equal.
Short story: Fella brings me 2 wheels, one ugly steel and another pretty aftermarket one and asked me what the difference was. I measured the rim diameter, width, backspacing, bolt pattern and told him there was no difference except that one was prettier than the other.
Hope I helped out and didn't confuse anybody. Just speaking from experience.
