Offset
The offset of a wheel is the distance from its hub mounting surface to the centerline of the wheel. The offset can be one of three types.

Zero Offset
The hub mounting surface is even with the centerline of the wheel.

Positive
The hub mounting surface is toward the front or wheel side of the wheel. Positive offset wheels are generally found on front wheel drive cars and newer rear drive cars.

Negative
The hub mounting surface is toward the back or brake side of the wheels centerline. "Deep dish" wheels are typically a negative offset.

If the offset of the wheel is not correct for the car, the handling can be adversely affected. When the width of the wheel changes, the offset also changes numerically. If the offset were to stay the same while you added width, the additional width would be split evenly between the inside and outside. For most cars, this won't work correctly.

See pic



This should help too http://www.1010tires.com/WheelOffsetCalculator.asp

And if all fails and this still sounds like mumbo-jumbo lets put it this way the larger the # the larger the lip of the wheel is going to be or stick out from your hub.

See pic's





I hope this helps and if this is a repost mods please deleat!
Thanks!

 

Oh yeah one more thing. My friend had 20x9 and 20x10's in the back with no probs. I would only go as far as 19 is this set up but thats just me.

 

nice avatar!

 

Yeah! I noticed that before reading the thread. Then thought MM started this post.