The offset, measured in millimeters, can be negative or positive, and is the distance from the hub-mounting surface to the rim’s true center line. A positive offset means the hub-mounting surface is closer to the outside edge of the wheel, i.e. the wheel wraps around the hub and brake hardware more deeply; a negative offset means the hub-mounting surface is closer to the inside edge of the wheel and wheel sticks outwards more than inwards.
Negative Offset wheels have their mounting face toward the rear of the wheel – powerful rear-wheel drive cars often have wheels with negative offset. This is the contributing factors of being a bigger “lips” rim.
When selecting aftermarket wheels, a wheel with too little positive offset will be closer to the fender, and one with too much positive offset will be closer to the suspension components. Wheel width, offset and tire size all determine the way a particular wheel/tire combination will work on a given car.
To maintain handling characteristics and avoid undue loads on bushings and ball joints, the car manufacturer’s original offset should be maintained when choosing new wheels unless there are overriding clearance issues.
The hub mounting surface is even with the center line of the wheel.
The hub mounting surface is located in the front half of the wheel closer to the wheel face. This tucks the entire wheel in toward the brakes and vehicle suspension. Positive offset wheels are generally found on front-wheel drive cars and newer rear-wheel drive cars.
The hub mounting surface is located in the back half of the wheel closer to the back lip flange. This moves the wheel out away from the vehicle brakes and suspension. “Deep dish” wheels and wheels for lifted trucks are typically a negative offset.