offset vs. backspacing

[jake72ss]

how does offset translate into backspacing?
I would like to install zr1 replica wheels on my 72 chevelle, there are 2 offsets available 36 and 50mm i think. just trying to figure out which one
will work the best and where I can get the needed adapters.

Thanks,
Jake

[Nine Ball]

Google brings up a few simple conversion calculators.

http://www.autolounge.net/calculators/tirespacing.html

Offset is measured from the wheel width centerline to the backside of the mounting pad. 0 offset means the lug pad is dead center of the width of the wheel. Then you can have + or - values, depending on which direction the lug pad is located relative to center. + positive offset means the lug pad is towards the outside of the wheel, beyond the center line. Negative offset is when the lug pad is below the center line, towards the backside of the wheel.

Backspacing is measured from the backside of the wheel lip to the backside of the lug pad.

[alowerlevel]

http://www.rims-n-tires.com/rt_specs.jsp