Backspacing explanation

[Member # 77]

Since I was confused on Backspacing of a rim I thought I would post this for all the other rookies on the forum.

Thanks to jdpolzin for setting me straight on it.


How to Measure Wheel BackSpace:

Items required to measure wheel backspace:
Tape measure
Straight edge
Wheel w/o tire (preferred)

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.


Info came from:
https://www.rsracing.com/tech-wheel.html#backspace

 

[Dennis Kirban]

Good explaination......

What throws people off trying to figure it out is the fact the tire bead rides in the 7 inch space on the factory 15 by 7 rim however, the overall width of the rim the lip to lip is really 8 inches...

Your diagram works....having produced various wheels for chevy mopar buicks over the years took me awhile to comprend the theory. (math was never my strong suit)

I member when we first made the GNX style rims in the 16 by 8 style. No one had any idea where the center had to be so they would clear front and rear. I had several made with various offsets took my 87 GN to a tire place and said mount this tire on these rims until we find one that fits front and rear.....

Course that doesn't always work since most of our cars are not even sitting on the frames straight and 1986 models and back had different springs making the front end sit lower....

Sorry to ramble on just pointing out a few more tips on the subject.....

denniskirban@yahoo.com

 

[longball]

Backspacing info

Thanks for sharing. Backspacing rookie here........