How to measure a wheel hub

Vehicle wheels consist of different elements, including the wheel hub. Not all wheels will fit all vehicles in the same class.

Therefore, it’s critical to know how to measure a wheel hub accurately. This includes measurements of:

• Wheel hub bolt pattern, and
• Wheel hub bore size.

Measuring the Wheel Hub

The wheel hub is the central rotating part that holds the wheel in place. It contains bearings and connections for ABS and tracking sensors. To measure the wheel hub, you first need to remove the wheel.

You can do this with a wrench, once you have lifted the vehicle using a jack or hydraulic lift.

Next, to access the wheel hub, you’ll need to remove the brake drum. Loosen it to remove it from the wheel.

You’ll then see the exposed wheel hub, ready for measurement. Measure across the middle of the wheel hub to get the diameter.

How to Measure Wheel Hub Bolt Pattern

The wheel hub bolt pattern is the number of bolts lugs on the hub and the diameter of the circle in which they are arranged.

The pitch circle diameter (PCD) is the number of wheel bolts and the diameter of an imaginary circle if you drew it through the middle of each of the bolts in the pattern.

If you are swapping wheels, your new wheel will need an identical PCD to the one you’re replacing.

To get the PCD you must measure the wheel bolt pattern:

• In five-bolt patterns, start from the middle of one lug and measure to the outside of the next but one lug
• In four or six-bolt patterns, measure from the middle of one lug to the outside of the opposite lug in the pattern.

The PCD value you get will be the number of lugs multiplied by the ring diameter, for example: 5 x 104.

How to Measure Wheel Hub Bore Size

The wheel hub size needs to match the centre bore of the wheel perfectly. The centre bore is the hole in the middle of the back of the wheel.

Wheels do come in different hub and centre bore sizes.

Generally, callipers won’t fit inside a wheel, so you will need a ruler or tape measure for this.

Normally the centre bore is covered by a cap, but you can easily pop this off to see the hole underneath.

How to Get the Right Fit

You have three measurements for fitting a new wheel hub:

• Wheel hub
• Bolt pattern
• Bore size.

You cannot fit a new wheel if the hub diameter is wider than the bore size.

However, if the bore size is larger than the hub diameter you can use wheel spigot rings.

Typically made from polycarbonate or aluminium, these rings are designed to fit between the car wheel hub and the rim to ensure the bore size works with the hub’s dimensions.

By selecting the right size of spigot ring, you can still mount the wheel safely even if its central bore is too big for the wheel hub.

Find Your Perfect Wheel Hub

For more information about wheel hub assemblies, replacement kits and services for HGV’s and other commercial vehicles, please call us on 0161 370 3344 or fill in our contact form and we’ll be in touch as soon as possible.