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.

1. 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.

2. 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.

3. Wheel Bolt Pattern

The bolt pattern, or lug pattern, refers to the number of bolt holes in a wheel and the diameter of an imaginary circle drawn through the center of each hole. It's specific to each vehicle and typically consists of 4, 5, 6, or 8 lug holes for most cars, trucks, and SUVs.

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.

To measure the bolt pattern on a wheel with an even number of holes, simply measure from the center of one bolt hole to the center of the hole directly across from it. For wheels with an odd number of holes, you'll need a special bolt gauge. You can estimate the measurement by measuring from the center of one bolt to the space between the two bolts across from it, but keep in mind this will only be an approximation.

4. 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.

Most modern wheels have a positive offset. The right offset ensures proper wheel placement in the wheel well, so choosing the correct offset is critical to avoid rubbing and ensure smooth operation.

Additional Fitment Considerations:

Wheel Backspacing -
Backspacing measures the distance from the back edge of the wheel to its mounting surface. To measure backspacing, lay the wheel face down, place a straight edge across the inner lip, and measure the distance from the mounting surface to the straight edge.

While backspacing is related to offset, it isn't the same thing. Backspacing combines offset with wheel width, which is especially important when considering wider wheels. If you're upsizing, the offset may need to change to ensure proper clearance and prevent tire or rim rubbing.

Plus Sizing -
If you're thinking of upgrading to larger wheels and tires, this process is known as plus sizing. For example, you might move from a 16-inch wheel to a 17-inch, 18-inch, or even 20-inch wheel. Plus sizing requires choosing tires with a shorter sidewall (lower profile) to keep the overall diameter of the wheel and tire combination as close to the stock size as possible.

If you're interested in plus sizing your wheels and tires, give us a call. Our wheel specialists are ready to help you find the perfect combination for your vehicle.

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 and fitment is crucial.