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Turbo Grocery Getter
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Not sure if everyone understands offset, I know i didnt...

http://www.car-torque.net/forum/index.php?showtopic=1766

Offset:
(IMG:https://www.tirerack.com/images/wheels/tech/offset.gif)

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. 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.

The bolt pattern or bolt circle is the diameter of an imaginary circle formed by the centers of the wheel lugs. Bolt patterns can be 4, 5, 6, or 8 lug holes. A bolt circle of 4x100 would indicate a 4 lug pattern on a circle with a diameter of 100mm.
(IMG:http://www.tirerack.com/images/wheels/tech/4bolt.gif)
The diagram indicates the proper measuring methods. 6 lug wheels are measured like the 4 lug wheels.


The centerbore of a wheel is the size of the machined hole on the back of the wheel that centers the wheel properly on the hub of the car. This hole is machined to exactly match the hub so the wheels are precisely positioned, minimizing the chance of a vibration. With a hubcentric wheel, the lug hardware will not be supporting the weight of the vehicle, all they really do is press the wheel against the hub of the car. Some wheels use high quality, forged centering rings that lock into place in the back of the wheel. This is an acceptable alternative.


nathan
 
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