Originally Posted by
MarkA
It's basically a measure of how far from the center of the wheel that the wheel is mounted on your car. Or, to simplify, how far out the wheels/tires will stick.
For an explanation that comes from a full-scale car website but is still applicable to our stuff, read this:
http://www.tirerack.com/wheels/tech/...jsp?techid=101
In RC terms, stick with wheels made specifically for your car and you'll be happy.
+1 To what MarkA said.
If you use a small or negative offset the wheels can rub against your internals like shock bottoms etc when you turn, too large or positive and it can rub agains shell or be too wide for a specification.