Wheel Backspacing VS Wheel Offset: Charts and Table Included

If you want to get a new set of wheels, then you need to familiarize yourself with the terms backspacing and offset. They measure specific parts of a wheel and they determine a wheel’s position relative to the vehicle. If you don’t account for these measurements, your new wheel and tire combination might rub against your vehicle’s fender or other components.

What Is Wheel Offset?

The offset of a wheel is determined by measuring the distance between its centerline and the mounting surface. A wheel’s centerline can be identified by measuring the wheel’s width and simply dividing it into two equal parts. Meanwhile, the mounting surface is the part of the wheel that makes contact with your vehicle’s wheel hub. Millimeters are the standard unit of measurement for offset. You’ll often see that they can either be positive, zero, or negative.

A positive offset means the mounting surface extends beyond the centerline and closer to the wheel’s face. Having a negative offset means the mounting surface is located farther back on the wheel. Zero offset indicates that the mounting surface of the wheel is on the centerline.

Assuming that you don’t modify your vehicle’s suspension, the wheel offset will affect how much of the wheel will be sticking out from your fender. Wheel offset will also have a pronounced effect on your vehicle’s look. Having a higher positive offset will result in a wheel with a flatter face. Meanwhile, a lower negative offset will have a deep lip.

What Is Wheel Backspacing?

Backspace is the distance from the inside edge of the wheel to the mounting surface. Unlike the offset measurement, backspacing measurement is often done in inches. Backspacing is an old method to determine how far the vehicle’s mounting pad extends into the wheel. More backspace means the wheel hub is located deeper into the wheel. However, this puts the wheel closer to suspension components, increasing the chance of rubbing.

Correct backspacing should provide enough space for the suspension, brakes, and steering system to function without interference from the wheel. Having a positive offset increases backspace, while a negative offset decreases backspace.

Do Wheel Spacers Add or Subtract Wheel Offset?

People who get wheels with different offset measurements can add spacers. But what do spacers do? Wheel spacers are just a low-cost method of creating room between the wheel and your vehicle’s steering components and brakes.

Using wheel spacers will push the mounting point further out, allowing wheels with a negative offset to fit into the wheel well. Spacers can also allow owners to install larger tires because they move the wheel away from the hub. Spacers can also simply make the wheels sit wider. However, installing spacers can also increase the stress on wheel hub components.

You shouldn’t confuse wheel spacers with wheel adapters. Wheel adapters change the bolt patterns of the wheel hub so that wheels can fit. Wheel spacers simply add clearance between the wheel and the hub.

Finding Your Wheel’s Backspacing and Offset

To find your wheel’s backspace measurement, simply measure the distance from the inner edge of your wheel to the mounting surface. Once you have the backspace measurement, you can calculate your offset measurement. But first, you must determine your wheel’s centerline by dividing the wheel width in half. To find your wheel width, simply find the specified tire mounting width indicated on the wheel. Once you have your wheel width, it’s common practice to add an inch to it to account for the wheel’s outer lips before dividing it by two.

In the graph below, you’ll find the corresponding offset for a wheel with a backspace of 3.5” and a wheel width of 5.5”. Calculating for the centerline involves adding an inch to the wheel width of 5.5” which gives us a value of 6.5”. Dividing this number by two gives us a centerline of 3.25”. To find the offset, subtract the centerline of 3.25” from the wheel backspace measurement of 3.5” . This will give us a measurement of 0.25”. Since offset is typically represented in millimeters (mm), we need to convert it to inches by multiplying this figure by 25.4. This will give us a value of 6.35.

You can find the offset measurements of wheels with different backspace and wheel width values below:

Dangers of Incorrect Wheel Offset

Now that you understand how wheel offset affects how the wheel sits against your vehicle’s body, you might be tempted to pick wheels that are offset to suit your preferred vehicle look.  However, you need to be careful when doing so. Having too much positive or negative wheel offset has negative consequences, and you never want to sacrifice safety for style. If you plan to change your wheels’ offset, enlist a trusted mechanic’s help to avoid any complications. Otherwise, you might face these issues later on:

Too Much Positive Offset

Too much positive offset might allow the inner edges of your wheels and tires to rub against your vehicle’s suspension or body. This will wear these parts down and will eventually make driving your vehicle unsafe. Too much positive offset can also interfere with brake parts, which is disastrous in emergency situations. The tires might fail from the constant wear, leading to poor handling and instability when driving.

Too Much Negative Offset

On the other end of the spectrum, too much negative offset can lead to increased steering wheel kickback, meaning your vehicle’s steering wheel will shake or vibrate excessively when its tires hit a bump. Excessive negative offset can also put additional stress on the entire suspension system and lead to poor handling.

Running Different Wheel Offsets for Winter Tires

Take note that steering wheel offsets will affect your tires as well. If you have positive offset wheels and need to switch to winter tires, make sure they match the wheel’s offset. Using tires that don’t match your wheel offset will likely make them stick out past your vehicle’s fenders or wheel wells. That type of offset is illegal in certain areas, not to mention the added road salt, dirt, and chemicals that’ll get on your wheels where the fenders can’t protect them.

Wheel offsets are no doubt a fun aesthetic change you can make to your vehicle. Just don’t forget to make sure they’re done the right way and are legal in your area.