Wheel Backspacing and Offset Explained

Wheel Backspacing and Offset Explained

Last Updated September 29, 2016

The Fundamentals

Typically with aftermarket wheels, a common question is “will XXXmm wide tires rub if I’m lowered,” or something along those lines. Yes, the width of the tire is part of it, but the offset of the wheel also plays a large part in how the wheel will sit inside the wheel-well as well. That’s why it’s important to understand the fundamentals when it comes to wheel backspacing and offset so you’re able to pick up the right rims for your Mustang!

Mustang Bolt Patterns

Perhaps the easiest concept to explain in this article would be bolt patterns. Bolt patterns are simply the spacing between each bolt hole on the wheel for your hub. On pretty much any Mustang minus 4-lug models, the bolt pattern is 5 x 114.3mm or 5 x 4.5”. The 5 stands for five lug and the 114.3mm or 4.5” is the distance between the center of each bolt.

Mustang Wheel Offset

Mustang Wheels At CJ Pony Parts Black Chrome Rovos Durbans (+23mm)

The most basic definition of wheel offset is the distance, usually in millimeters, from the wheel-mounting surface or hub to the centerline of the wheel. Typically most OEM wheels have a positive offset putting the hub towards the outside of the car and flush with the outer rim.

In more recent years, a popular look for any Mustang has been the deep concave look. This look is achieved by a negative offset which places the hub further in the barrel of the wheel which makes for a killer look! A good example of this would be a lot of the Velgen Wheels and Rovos Wheels on 1994+ Mustangs.

There are three different types of wheel offset:

  • Positive Offset: Your wheels will mount further inward since the hub-mounting surface is towards the outer rim of the wheel. This will give you better clearance on the outside edge of the tire and fender, but less clearance between the inside of the wheel and the shock or strut. On cars with independent rear suspension (IRS), you really need to watch the offset and overall width of your rear wheels for this reason.
  • Zero Offset: This occurs when the outside of either side of the wheel to the hub-mounting surface is equal. Another way of looking at this is that the hub of the wheel sits directly in the center of the barrel.
  • Negative Offset: A lot of Mustang owners prefer to have a negative offset with their aftermarket wheels. By pushing the hub-mounting surface towards the inside of the wheel, you’ll naturally get the deep concave profile while pushing your tires out closer to the fender for a flush look.

Mustang Wheels At CJ Pony Parts
Positive vs Zero vs Negative Wheel Offset

Mustang Wheel Backspacing

Mustang Wheels At CJ Pony Parts S197 Wheels On An SN95 Mustang

If you understand the concept of wheel offset, then the definition of backspacing will be a breeze! This is due to the fact that wheel backspacing is essentially dictated by the offset.

The measurement for wheel backspacing is the distance, in inches, between the inside of the wheel, or brake side, to the hub mounting surface. Backspacing of a wheel is significant because it will tell you the clearance of a given wheel and how much it will stick out from your fender.

For example, if you put an SN95 wheel on an S197 it will stick out from the fender and may even rub due to different backspacing. And vice versa, because an S197 wheel will look skinny on an SN95 due to the fact it will sink further in.

Picking The Right Wheels

When you’re in the process of researching and choosing the right aftermarket wheels for your Mustang, be sure to learn the meaning of offset and backspacing before purchasing. So many people out there find a great deal, mount and balance with tires and then become disappointed when they finally get them on the car to find out that they sit too far in or out from where they imagined.

Be smart and do your research before buying, it’ll make you that much happier once you finally do get the wheels you’re after to know they’ll sit perfectly on your Mustang!

Wheel Backspacing and Offset Explained

Understanding the concept of wheel offset and backspacing can be confusing for someone who may be just starting to look for an aftermarket set of wheels and tires. Each Mustang generation has a particular set of offset and backspacing numbers that work best with the fitment around that car’s suspension wheel-well.

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Regardless of what style, finish and size wheel you’re looking for, CJ Pony Parts has the selection you need to outfit your S550 with the rims and tires that will set your car apart from the rest! Be sure to give us a call or order online and don’t hesitate to let us know if you have any questions. We are always happy to help!