Can someone translate these wheel measurements to Back Space

[waynieZ]

Like the title says can someone translate these wheels to back space so I can figure spacers to use them for rollers? Or is there a conversion chart someone knows of?
The rear are 18x10 with a positive 42mm offset from center, the front are 18x8.5 with +36mm

My car is configured for 18X8 front and 19X12 rear both with 5" back space.

Thanks

[1Bad68Cat]

Like the title says can someone translate these wheels to back space so I can figure spacers to use them for rollers? Or is there a conversion chart someone knows of?
The rear are 18x10 with a positive 42mm offset from center, the front are 18x8.5 with +36mm

My car is configured for 18X8 front and 19X12 rear both with 5" back space.

Thanks

I assume if you include the bead/lip of the wheel, the wheels are actually 11 and 9.5 wide. Therefore on the front the BS is 9.5/2+(36/25.4)=6.17. The rears are 11/2+(42/25.4)=7.15

[kevin_l]

CCW has a great little calculator

http://www.ccwheel.com/technical-converter.php

[waynieZ]

Thank you guys this stuff make my head spin.