What is "backspacing" and "offset"?

I have read in a lot of places on this site about "backspacing" and "offset". What is that?

 

Seek and you shall find...

https://www.rsracing.com/tech-wheel.html

 

They are two different measurements of the same thing. The distance from the surface of the wheel that mounts on the hub to the inner edge of the barrel of the wheel. An 8" wide wheel that has a 4" backspacing has 0 offset - the wheel mounting point is exactly in the middle of the wheel. And the offset is usually measured in mm and backspacing in inches.

 

Hi there;

I'm confused, I've seen the same explanation you give elsewhere, but was recently looking at wheels on the American Racing website. Many of their 16x8 wheels are reported as having 4.5 backspacing and 0 mm offset ! It does not add up ! For such numbers the wheel should be 16x9, right ? Any ideas ? I looked at some of their other sizes and found similar inconsistencies...

I'm looking for 16x8 wheels for my new Tacoma 2009, and would like to keep the OEM offset so as not to cause wheel bearing problems...and keep the same axle width... Any suggestions ?

 

Backspacing and offset are not the same thing. Backspacing is the distance from the back of the rim to the hub mounting surface. Offset is the distance between the hub mounting surface and the centerline of the wheel.

More info...
http://www.tirerack.com/wheels/tech/techpage.jsp?techid=101&currentpage=92

njaimo.... I agree! Those AR specs make no sense at all