What Is a Wheel Center Bore?
A center bore is a hole in the center of a wheel that fits over the car hub. The hub is part of the axle where the wheel is mounted. The primary function of the center bore is to prevent the wheel from wobbling on the axle. A center bore that’s too small can cause damage to the vehicle’s suspension​​.
How to Measure the Center Bore of Wheels?
Measuring the center bore of a wheel involves determining the size of the hole on the backside of the wheel. This measurement is in millimeters (mm) and is critical when shopping for wheels or hub-centric rings to ensure proper fit and vehicle compatibility. Here’s a simple guide to measuring the center bore of wheels:
- Locate the Center Bore: The center bore is the large hole in the middle of the wheel on the backside. It’s where the wheel fits onto the hub of the vehicle.
- Prepare Your Tools: You’ll need a precise measuring tool like a caliper for accurate measurement. Calipers can measure the diameter of circular objects accurately and are ideal for this purpose.
- Measure the Diameter: Place the caliper’s ends across the widest part of the center bore. Make sure to measure from one side of the bore directly to the opposite side. The technician should measure from the interior edges, as this will give you the diameter of the hole.
- Ensure Accuracy: It’s essential to measure the diameter in several spots around the bore to ensure accuracy. This is because the bore could be slightly out of round, and measuring in multiple places helps account for any irregularities.
- Record the Measurement: Write down the measurement in millimeters. If your caliper provides readings in inches, convert the measurement to millimeters for standardization (1 inch = 25.4 mm).
- Compare with Vehicle Specifications: Once you have the center bore measurement, compare it with the specifications of your vehicle’s hub. This comparison is crucial for ensuring that the wheel fits properly over the hub without issues like vibration or misalignment.
Importance of Matching Center Bore Size
The fit between the wheel’s center bore and the car’s hub is crucial. Wheel studs or bolts hold the wheel in place over the spigot (part of the hub), necessitating a perfect match between the wheel’s center bore and the spigot’s size. Mismatches can lead to improper wheel alignment and increased wear on components. Spigot rings are used to adapt the center bore size to fit different hubs. This ensures a snug and safe fit​​.
Hub-Centric vs. Lug-Centric Wheels
Manufacturers design the wheels either hub-centric or lug-centric. Hub-centric wheels rely on the fit between the wheel’s center bore and the vehicle’s hub for proper alignment and support.
Lug-centric wheels, on the other hand, do not depend on the center bore for alignment; instead, they use the lug nuts to secure and center the wheel. Manufacturers design some wheels to fit multiple vehicle models. They use centering ring systems to adjust the bore size for different hubs. These rings maintain the wheel’s precise position as the lug hardware is torqued down​​.
What Happens If the Center Bore Is Too Small or Too Large?
If a wheel’s center bore is too small, it won’t fit onto the hub of the vehicle. If try to fit forcefully, it puts strain on the suspension system and can damage it. On the other hand, if the center bore is too large, it is not possible to center the wheel on the hub. This can lead to vibrations while driving. In both cases, driving safety and vehicle performance are compromised.