I was told tht the 18x 8.5 were a 48mm offset. Please don't flame me for asking this ? But what does the offset mean? Does it have anything to do with how far the spokes stick out from the lip? Or no
The hub mounting surface is even with the centerline of the wheel.
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.
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. We have test fitted thousands of different vehicles for proper fitment. Our extensive database allows our sales staff to offer you the perfect fit for your vehicle.
Again Information from TireRack.
17x9 wheel w/ 0 offset.
9" will be split directly in the middle.
+20 offset: 94.3mm of rim on the outside or street side; 134.3mm of rim will be on the inside.
You can figure out how it will clear by measuring suspension. from bottom of suspension to hub. from there you can see where your offset has to be. if you have 5" of room then you can run a 17x9 +15mm offset without rubbing on suspension.
Edit: I +1 you^^^ I was looking for this post i did a while back... Including same exact info... I wish people would search most days.
Also STICKIED IN THIS SECTION!: Official Fitment Info. Thread; Offsets,Spacers, Fender Work, Tire Setup and Alignment