[tommycheng1728]

for a 8" wide wheel, all around, if 40 offset is good, is 45 offset better?

 

[Subdriver]

for a 8" wide wheel, all around, if 40 offset is good, is 45 offset better?

Not necessarily. Changing the offset moves the center of the wheel in relation to the axle centerline (e.g. out farther). This upsets the whole design of the suspension. In general, you want to keep the original centerline of the wheel where the designer intended.

Here is a short description:
http://www.tirerack.com/wheels/tech/techpage.jsp?techid=101