Wheel Center Bore Sizes and Hub Fitment Guide

What Is Wheel Center Bore and Why Does It Matter?

The wheel center bore (also called hub bore or hub pilot diameter) is the large hole at the center of a wheel that fits over the hub's mounting lip on the vehicle. This machined lip centers the wheel when it is installed. If the center bore matches the hub diameter exactly, it is called a hub-centric fitment. The wheel is supported by the hub, which reduces stress on the lug studs or bolts and helps prevent vibration.

If the wheel's center bore is larger than the vehicle's hub, you can use hub-centric rings (spigot rings) to fill the gap. These rings have an inner diameter that matches the hub and an outer diameter that matches the wheel bore, effectively making the wheel hub-centric. If the bore is smaller, the wheel will not fit without machining or adapters, which is generally unsafe and not recommended.

Center bore is always measured in millimeters. For example, many Honda vehicles have a 64.1 mm hub bore, while many BMWs use 72.6 mm. Getting this dimension correct is essential for safe and smooth driving.

How to Find and Measure Wheel Center Bore

How to Check Wheel Center Bore on a Wheel You Have

If you have a wheel off the car, you can measure the center bore directly. The most accurate method uses a digital caliper. Place the caliper's inside measuring jaws into the hole from the back side of the wheel (where it contacts the hub). Expand the jaws until they touch opposite edges of the bore, then read the measurement in millimeters. Take several measurements at different points to ensure the bore is round.

If you only have a tape measure, you can get a rough idea by measuring across the hole at its widest point. However, tape measures are not precise enough for critical fitment—use a caliper whenever possible. Alternatively, you may find the center bore stamped on the wheel, but this is not always present.

How to Find Wheel Hub Bore on Your Vehicle

To find your vehicle's hub bore, you can measure the hub mounting lip on the car. Remove the wheel and measure the outer diameter of the lip that protrudes through the wheel. Use a caliper for accuracy. If you cannot measure directly, refer to a vehicle-specific center bore chart or your owner's manual. Many manufacturers publish this specification.

Using Hub Centric Rings: Sizing and Selection

When using hub-centric rings, you need two measurements: the inner diameter of the ring must match your vehicle's hub bore, and the outer diameter must match your wheel's center bore. For example, if your car has a 56.1 mm hub and your aftermarket wheel has a 73.1 mm bore, you need a ring with 56.1 mm inner diameter and 73.1 mm outer diameter. Rings are typically made of plastic or aluminum and are inexpensive. Always confirm the dimensions before ordering.

Vehicle-Specific Center Bore Sizes

Here are common hub bore sizes for popular brands. Note that some models within a brand may differ, so always verify for your specific vehicle.

For the Subaru BRZ and Toyota GR86, the hub bore is 56.1 mm, so if you buy aftermarket wheels with a larger bore (e.g., 73.1 mm), you need hub centric rings with 56.1 mm inner diameter and the wheel's outer bore diameter.

How to Measure Rim Center Bore Step by Step

1. Place the wheel face down on a soft surface to protect the finish.
2. Set your digital caliper to measure inside dimensions.
3. Insert the jaws into the center hole from the back side (the side that mounts against the hub).
4. Open the jaws until they touch opposite points on the bore wall. Ensure the caliper is perpendicular to the hole for an accurate reading.
5. Read the measurement in millimeters. Repeat at several angles to check for roundness; if measurements vary, the bore may be damaged or not perfectly round.
6. Compare your measurement to your vehicle's hub bore. If the wheel bore is larger, choose appropriate hub-centric rings.

Understanding Hub-Centric vs. Lug-Centric Wheels

Hub-centric wheels have a center bore that exactly matches the hub diameter. The wheel is centered by the hub, and the lug nuts or bolts simply clamp the wheel in place. This is the factory setup for most modern cars and provides the most reliable centering.

Lug-centric wheels have a larger, non-matching center bore and rely on the lug nuts or bolts to center the wheel. This is common on many aftermarket wheels. While lug-centric can work, it requires careful torqueing in a star pattern and may be more prone to vibration if not perfectly centered. Using hub-centric rings converts a lug-centric setup to hub-centric, improving safety and smoothness.

Common Mistakes and Tips

• Never force a wheel with a too-small center bore onto a hub; it can damage both components and is unsafe.
• Always measure in millimeters; mixing units leads to errors.
• If using hub-centric rings, ensure they fit snugly in the wheel and hub; loose rings can cause vibration.
• Check for corrosion on the hub and wheel bore; clean surfaces before mounting.
• Re-torque wheels after 50–100 miles of driving when installing new wheels or rings.