- Offset: Offset refers to the distance between the centerline of the wheel and the mounting surface where the wheel attaches to the hub. It determines how the wheel and tire assembly sit in relation to the vehicle's suspension and body.
Positive Offset: When the mounting surface is towards the front face of the wheel (wheel's outer side) or towards the vehicle, it is called positive offset. This makes the wheel sit closer to the vehicle's suspension. Most modern cars have positive offset wheels.
Negative Offset: When the mounting surface is towards the rear face of the wheel (wheel's inner side) or away from the vehicle, it is called negative offset. This makes the wheel sit farther out from the vehicle's suspension. Some custom wheels or off-road vehicles may have negative offset wheels.
- Backspacing: Backspacing is the measurement from the mounting surface to the inside edge of the wheel. It determines the clearance between the wheel and suspension components, as well as the position of the tire in the wheel well.
- Backspacing Calculation: To calculate backspacing, measure the distance between the mounting surface and the back edge of the wheel (the side facing the suspension). It's important to note that backspacing is measured in inches.
- Relationship between Offset and Backspacing: Offset and backspacing are related to each other. You can calculate backspacing using the offset and width of the wheel:
- Backspacing = (Wheel width / 2) + (Offset / 25.4)
Keep in mind that wheel width is typically measured from bead seat to bead seat.
- Effect on Vehicle Handling and Appearance: Understanding offset and backspacing is crucial when selecting aftermarket wheels or considering wheel spacers. Here's a general idea of how these factors can affect your vehicle:
Positive Offset: Provides better stability and handling for most vehicles. It pushes the wheel inward and keeps it within the wheel well. Too much positive offset may cause clearance issues with suspension components.
Negative Offset: Widens the vehicle's track width, which can improve stability, particularly in off-road vehicles. However, it may require fender modifications to prevent tire rubbing against the vehicle body.