Wheel offset and backspacing help determine where your wheels and tires sit on your truck. The right fit gives them enough room inside the fender while keeping them clear of the brakes and suspension. Offset is measured in millimeters from the center of the wheel, while backspacing is measured in inches from the back edge of the wheel. Both measurements help show how far inward or outward the wheel will sit.
When these measurements are right, your wheels fit properly and have the clearance they need. When they are wrong, you may run into tire rubbing, added wear on wheel bearings, or other fitment problems.
Because fitment can vary from one truck to another, always confirm that a wheel matches your exact year, make and model. You should also factor in your suspension setup before ordering.
What Is Wheel Offset?
Wheel offset is the distance between the wheel’s mounting surface, where the wheel bolts to the hub, and the centerline of the wheel. It is measured in millimeters and is often stamped on the wheel as “ET” followed by a number.
There are three main types of wheel offset:
- Positive offset: The mounting surface sits closer to the outside of the wheel, pulling the wheel farther inward. This is common on factory trucks and daily drivers.
- Zero offset: The mounting surface lines up with the wheel centerline, creating a neutral position between tucked-in and pushed-out.
- Negative offset: The mounting surface sits closer to the inside of the wheel, pushing the wheel farther outward. This creates the wider “poke” look often seen on lifted and off-road trucks.
An easy rule to remember is that a more positive offset pulls the wheel inward, while a more negative offset pushes it outward.
What Is Backspacing?
Backspacing is the distance from the wheel’s mounting surface to the inner edge of the wheel, measured in inches. More backspacing moves the wheel farther inward toward the suspension, while less backspacing moves it outward toward the fender.
Backspacing and offset are closely related, but they measure wheel position from different points and use different units. That’s why you’ll often see both measurements used when discussing wheel fitment.
Offset vs. Backspacing: How They Relate
If you know the wheel width and offset, you can calculate backspacing with this formula:
Backspacing (inches) = (wheel width ÷ 2) + 0.5 + (offset ÷ 25.4)
The extra 0.5 inch accounts for the wheel lip, and dividing the offset by 25.4 converts millimeters to inches.
For example, an 8-inch-wide wheel with zero offset has 4.5 inches of backspacing: 8 ÷ 2, plus 0.5. A positive offset increases the backspacing, while a negative offset decreases it.
How Do You Read Wheel Size and Fitment Numbers?
Every wheel is marked with several measurements that help determine whether it will fit your truck. Here’s what the most common numbers mean:
- Diameter and width: A size like 18×9 means the wheel is 18 inches in diameter and 9 inches wide.
- Offset: Usually shown as “ET” followed by a positive or negative number in millimeters.
- Bolt pattern: A measurement like 6×139.7 that must match your truck’s bolt pattern.
- Hub bore: The diameter of the center hole in the wheel. If the bore is larger than your truck’s hub, hub-centric rings may be needed for proper fitment.
Wheel width and offset work together to determine backspacing, so both are important when checking fitment. For hub rings, lug nuts and other mounting hardware, browse wheel accessories.
How to Measure Backspacing Yourself
If a wheel isn’t clearly marked, you can measure its backspacing in about two minutes:
- Lay the wheel face-down on a flat surface.
- Place a straightedge across the back of the wheel.
- Measure straight down from the straightedge to the wheel’s mounting surface.
That measurement is the wheel’s backspacing. It’s a useful way to double-check fitment when you’re working with a used wheel or one without clear markings.
How Offset Affects Stance, Rubbing, and Handling
Offset affects more than how your truck looks. Moving a wheel too far inward or outward can create fitment and handling problems.
Wheels That Sit Too Far Out
Too little backspacing or too much negative offset pushes the wheel farther outward. This can create a wider stance, but it may also cause the tire to rub against the fender when turning or when the suspension compresses.
Wheels that sit farther out can also throw more mud, water, and road debris along the side of your truck. Fender flares can add extra coverage, while mud flaps can help reduce spray and debris.
Wheels That Sit Too Far In
Too much backspacing or too much positive offset pulls the wheel closer to the suspension. If there isn’t enough clearance, the tire may rub against the inner fender liner, control arms, or other suspension components. Larger brake components may also have less room behind the wheel.
Offset can also change how the truck feels when steering and place extra stress on wheel bearings and steering components. Staying close to the factory offset is generally the best way to preserve the clearance and handling your truck was designed for.
What Offset Works for a Lifted or Leveled Truck
Lifting or leveling a truck changes the space available for your wheels and tires, so wheel fitment should be considered along with your suspension setup.
A suspension lift kit can create room for larger tires and may change which wheel offsets work best for your setup. A leveling kit raises the front of the truck to reduce the factory rake and can also make room for a larger front tire.
If you’re moving to wider tires, the right offset will depend on the tire size, wheel width, and suspension setup. Rather than choosing wheels based on size alone, consider how the complete wheel, tire, and suspension combination will work together.
You can browse aftermarket wheels to find options for your truck.
A Quick Word on Wheel Spacers
Wheel spacers sit between the wheel and hub, moving the wheel farther outward. This effectively reduces the offset and can provide additional clearance between the wheel and suspension components without requiring a different set of wheels.
If you use spacers, choose quality hub-centric options, torque them to the manufacturer’s specifications, and recheck them as recommended. You can find spacers and other mounting hardware under wheel accessories.
Frequently Asked Questions
What’s the Difference Between Offset and Backspacing?
Offset and backspacing are two different measurements used to describe wheel fitment. Offset measures the position of the mounting surface relative to the wheel’s centerline in millimeters. Backspacing measures the distance from the mounting surface to the inner edge of the wheel in inches.
Does Wheel Offset Affect Handling?
Yes. Changing the offset can affect steering feel and place additional stress on wheel bearings and steering components. The farther you move from the factory offset, the more noticeable those changes may become.
What Offset Should I Run on a Leveled Truck?
There isn’t one offset that works for every leveled truck. The right choice depends on your truck, wheel width, tire size, and leveling setup. Check the complete wheel-and-tire combination for your specific vehicle before ordering.
Will Wider Wheels or Tires Rub?
They can. Whether a wider wheel or tire rubs depends on factors such as wheel width, offset, tire size, and suspension setup. Checking the complete fitment before ordering can help prevent clearance problems.
How Do I Measure Wheel Backspacing?
Lay the wheel face-down on a flat surface and place a straightedge across the back of the wheel. Measure from the straightedge down to the wheel’s mounting surface. That distance is the wheel’s backspacing.
Build It Right the First Time
Getting wheel fitment right comes down to choosing offset and backspacing that work with your truck, tires, and suspension setup. With the right combination, you can get the stance you want without sacrificing proper clearance or fitment. Omni Garage stocks thousands of wheels, tires, and accessories ready to ship, with free standard shipping on orders over $200 in the contiguous US and real, US-based support if you need help confirming a fitment.
Level Up Your Vehicle!
At Omni Garage, we make it our mission to help your vehicle reach its highest potential at the lowest price. Whether you’re upgrading your wheels, fitting larger tires, or building out your truck for the road or trail, we have the parts and accessories to help you get the setup right.
