While the appearance of your wheels is important, ensuring they fit your vehicle properly is vital for both safety and performance. That's why understanding wheel size is crucial.

Wheel size is made up of four key dimensions: diameter, width, bolt pattern, and offset. Knowing these measurements will help you choose the right wheels for your vehicle. Let’s break them down using the example:

20x9 6x139.7 24

While this may look like a string of random numbers, it provides all the essential details about the wheel’s size. Here’s what it means:

Wheel Diameter: 20 inches
Wheel Width: 9 inches
Wheel Bolt Pattern: 6x139.7
Wheel Offset: 24 mm
Now, let’s dive deeper into each dimension to understand how they impact your wheel selection.

Wheel Diameter
The wheel diameter is the measurement across the face of the wheel, from bead seat to bead seat (where the tire and wheel connect), and is expressed in inches. In this example, the wheel diameter is 20 inches.

It’s important that the wheel and tire diameters match. For example, only a 20" tire will properly fit a 20" wheel. The wheel diameter is often stamped on the back of the wheel, typically on one of the spokes.

Wheel Width
Wheel width refers to the distance across the barrel of the wheel, also measured in inches from bead seat to bead seat. In this example, the width is 9 inches. Common wheel widths range from 6 to 14 inches.

Changing your wheel width can impact your tire's contact patch, which directly influences handling and performance.

Wheel Bolt Pattern
The bolt pattern consists of two numbers that describe how the wheel attaches to your vehicle. The first number indicates the number of bolt holes, while the second represents the diameter of the imaginary circle these bolt holes form. In our example, "6x139.7" means the wheel has 6 bolt holes arranged in a circle with a diameter of 139.7mm.

Bolt patterns vary, with common setups including 4-lug, 5-lug, 6-lug, and 8-lug patterns. The wheel's bolt pattern must match your vehicle's bolt pattern exactly for a secure and safe installation.

Wheel Offset
Offset measures the distance, in millimeters, from the wheel's mounting surface to its centerline. In this example, the offset is 24mm, meaning the mounting surface is 24mm closer to the front (outer) side of the wheel.

Offset can be:
Positive: The mounting surface is toward the front of the wheel.
Zero: The mounting surface is aligned with the wheel's centerline.
Negative: The mounting surface is toward the back of the wheel.
The correct offset is crucial for two reasons:

It prevents your wheels and tires from rubbing against brakes, suspension, or fenders.

It affects the vehicle’s stance, determining whether the wheels sit tucked inside the fenders or extend outward.

By understanding these key dimensions, you can ensure that the wheels you choose will fit your vehicle safely and look great.