This info came from
https://www.rsracing.com/tech-wheel.html#" target="_blank" rel="nofollow">
https://www.rsracing.com/tech-wheel.html#backspace Hope it may help.Backspace to Offset Conversion Chart The table below is a quick reference for finding offset, pick the rim width and follow the row over to the backspace of your wheel. Measuring Wheel Offset To calculate offset you'll need the following measurements:
Wheel backspace Wheel Width Wheel Center line (outboard flange to inboard flange measurement / 2) Subtract:
Wheel center line from Wheel backspace to get offset. If backspace is less than the wheel centerline the offset is negative If backspace is greater than the wheel centerline the offset is positive Tip:
To convert from inches to mm multiply by 25.4 To convert from mm to inches divide by 25.4 This info is at
https://www.rsracing.com/tech-wheel.html#" target="_blank" rel="nofollow">
https://www.rsracing.com/tech-wheel.html#backspace They have a great guide on wheel info.