When you begin searching for a new set of wheels and tires, it’s imperative that you get precise measurements to make sure the combination fits properly. This is to avoid having them rub against the fender or other vehicle components, causing unnecessary damage and an uncomfortable ride. Two important measurements that describe a wheel’s position are Offset and backspacing. While many people believe that the two are the same, they each have their own characteristics and affect the outcome of your ride’s stance differently.
Offset measures the distance between a wheel’s mounting surface and the centerline, while backspacing measures the distance between the mounting surface and the innermost lip. Both help determine which wheels are compatible with your vehicle and are crucial to know when shopping for aftermarket wheels. After all, you don’t want to invest in an expensive setup just to find out that they do not install properly. And while they can be described in relation to one another, we are going to delve into what offset and backspacing are so that you can get the perfect fitment for your vehicle.
Wheel Offset
In order to properly understand wheel offset, you first need to know the basic parts of a wheel assembly. A wheel’s offset describes its position so that it can freely rotate and not rub against the fender or brakes. Millimeters are the standard unit of measurement for offset, and it can be either negative, zero, of positive. A negative offset refers to a mounting surface that is situated closer to the back of the wheel. It gives vehicles that deep-dish look; so, -44 is deeper than -18. While many owners like the aggressive look associated with a negative offset, it can be an issue on some vehicles. A zero, or neutral, offset means that the wheel face is right in the center of the rim. A positive offset describes a mounting surface that extends past the centerline closer to the face of the wheel. The higher the number, the less lip there is and the more forward the wheel face will be. For example, a +20mm offset means that the face of the wheel leans more toward the outside of the vehicle than a +1mm offset.
Wheel Backspacing
To get your current backspacing numbers, measure from the wheel’s mounting plate to its inner lip. If you are looking to buy aftermarket wheels but are leaving your suspension the same, aim to keep the measurement as close to the stock backspacing as you can. If you are lifted or plan to install a lift kit with the new wheels, make sure to check with the product manufacturer to get the correct backspacing requirements since it will likely differ from the factory measurement. With that said, backspacing is usually a positive number, but it can be negative in some instances like on dually pick-up trucks. The amount of backspacing can really alter wheel positioning, so it’s important to keep that in mind when shopping for wheels. The correct backspacing will allow for enough room for the brakes, suspension, and steering systems to operate seamlessly without interference from the wheel. And, clearly, a positive number means more backspace (wheel protrudes further into the wheel well), while a negative number reduces backspacing (wheel protrudes less into the wheel well).
Quick Calculations
Here are some tips for figuring out the backspacing, centerline, and offset of your wheels.
- Measure the space in your wheel wells relative to the wheel hub.
- Backspace = The distance from back of the wheel to the wheel’s mounting space.
- Centerline = The wheel width divided by 2.
- Offset = Backspace – centerline, which will be positive or negative.
- Convert to millimeters by x 25.4 or convert to inches by / 25.4.
Conclusion
As you can see, offset and backspacing can really make or break the look of your car or truck. They also have a bigger role than that as they allow the suspension system and tires to work together. Higher backspacing can cause clearance issues and the rubbing of control arms and such. Lower backspacing means decreased wheel travel, a larger turning radius, and possible fender rubbing or bumper trimming. Still not sure about which wheel fitment to get? Have an idea of the style you want and give our expert sales team a call at 1-480-966-3040 or via email at [email protected]. We can help pick out the best offset / backspacing combination for your application.
