Wheel offset is a critical measurement that determines how far the wheel's mounting surface (the surface that contacts the hub of the car) is from the wheel's centerline. It plays a significant role in the wheel's position within the wheel well and can impact a vehicle's handling, aesthetics, and fitment. The offset is measured in millimeters and is typically stamped or engraved on the wheel, often in the form of ET (German "Einpresstiefe") followed by a number.
There are three primary types of wheel offsets:
Positive Offset: In a positive offset, the mounting surface is closer to the front (outboard) side of the wheel, meaning the wheel is positioned closer to the outside of the vehicle. This type of offset is common in most passenger cars and helps maintain stability and handling characteristics.
Zero Offset: With a zero offset, the mounting surface is at the wheel's centerline. This means the wheel is evenly positioned relative to the wheel well. Zero offset wheels are less common in modern vehicles but were more prevalent in older designs.
Negative Offset: In a negative offset, the mounting surface is closer to the back (inboard) side of the wheel, meaning the wheel is positioned further inside the vehicle's wheel well. Negative offset wheels are often seen in trucks and off-road vehicles, as they provide additional clearance for larger tires and suspension components. However, excessive negative offset can negatively impact handling and stability.
To measure the offset of a wheel, follow these steps:
Locate the Mounting Surface: Find the mounting surface of the wheel. It's the flat surface where the wheel makes contact with the vehicle's hub.
Measure to the Centerline: Measure from the center of the wheel (the point halfway between the inner and outer rims) to the mounting surface. This measurement, in millimeters, is the offset.
Determine the Offset Type: Depending on where the mounting surface falls concerning the wheel's centerline, you'll have a positive, zero, or negative offset.
For example, if you measure 25mm from the centerline to the mounting surface, the wheel has a positive offset of +25mm. Conversely, if you measure -10mm, it has a negative offset of -10mm.
It's crucial to understand the offset when selecting wheels for your vehicle, as it affects the wheel's position in the wheel well, tire clearance, and how the vehicle handles. When changing wheels, it's often recommended to stick as closely as possible to the factory-specified offset to maintain proper fitment and handling characteristics. However, if you're considering a different offset, consult with a wheel specialist at Factory Wheel Replacement or refer to your vehicle's specifications to ensure compatibility and safety.