What are wheel backspacing and offset? What's the difference?
Unless you go through a lot of different wheels and tires or spend your free time with suspension engineering, the terms backspacing and offset probably do not come up very often. Thankfully, Classic Industries is here to help with simple explanations and a useful diagram.
What is Wheel Backspacing?
Backspacing is the simply the distance from the bolt circle mounting surface to the inside of the wheel. If the wheels are zero-offset, the mounting surface is the along the wheel's centerline, which means the backspacing should be 1/2 the width of the wheel.
What is Wheel Offset?
Wheel offset is the distance between the wheel's bolt circle mounting surface and the rim centerline. If the mounting surface sticks out farther than the centerline, the offset is positive. If the centerline is farther outboard than the mounting surface, the offset is negative. An easy way to understand this is to remember that the typical deep-dish wheel has negative offset.
Why are Backspacing and Offset Important?
It is important to consider backspacing and offset when purchasing wheels. If the backspacing is too different from the original design, you may encounter steering problems as a result of the altered geometry. In the same way, if the offset of the new wheel is significantly different than original, the load on the wheel bearings is affected and can cause them to wear out sooner.
What is Wheel Bolt Pattern?
Wheel bolt pattern is the configuration of the wheel bolts on the hub. It is annotated in "A x B" format, where A is the number of wheel bolts, and B is the distance between bolts (measured according to the diagram above).
For example, the '67-'69 Camaro has a wheel bolt pattern of 5 x 4.75". The Camaro has 5-lug hubs, with five wheel bolts and five lug nuts per wheel—hence the first number. The second number is obtained by measuring from the back side of the top hole to the center of the opposite hole. In this case, it results in a measurement of 4.75 inches.
Why is Wheel Bolt Pattern Important?
Your vehicle's wheel bolt pattern must be considered before purchasing wheels. If the wheels you purchase do not match your car's wheel bolt pattern, you will not be able to install them. To check your car's wheel bolt pattern, you can either measure your current wheels using the above method, or search for "[your car's year, make, and model] wheel bolt pattern" on any web search engine.
If you're looking for a new set of wheels for your car, Classic Industries has tons of options to choose from! Click here to start shopping.