Explain "offset"

What does it mean when a rim says +27mm offset or -27mm offset? I am used to seeing terms of '4" backspace' rather than offset. Can someone tell me how to convert offset to backspace?

 

[Okrazie1]

Here's some info on offset that might help you out.

 

[RTStork]

Thanks, that helped some, but I still need to know how to convert offset to backspace.

 

[tbomb]

well, offset is the measurement from the point from the hub mounting surface to the center of the wheel, measured in mm.

backspacing is the distance from the hub mounting surface to the back edge of the wheel, measured in inches.

first convert inches to mm or mm to inches (25.4 mm = 1 inch.) then you basically just add 1/2 the width of the wheel to the offset and you get the backspacing.

example:

8" wide wheel with 25 mm (~1") offset. backspacing = 25mm + 4" = 1" + 4" = 5" backspacing.

 

[RTStork]

Thanks! Thats exactly what I needed!

 

[tbomb]

heh, no prob