Hub bore (Center bore) size - a definitive guide

What is called a wheel center bore?

A wheel center bore is a hole in the middle of the wheel that fits over the hub of your car. The hub is the part of the car's axle that the wheel attaches to. The purpose of the wheel center bore is to keep the wheel from wobbling on the axle. If the wheel center bore is too small, it can cause vibration and may damage your suspension. If it's too big, then your wheel may not fit properly on your car and could come loose while you're driving

Hub bore is usually measured in millimeters. To find out what size you need, measure the distance across the hub where the wheel attaches. You can also look up the specifications for your car to find the correct size.

So, the machined hole in the middle of a wheel that centers it properly on a vehicle's axle is known as its center bore. It's critical for a wheel to be "Hub Centric," because it lowers the risk of shimmy.

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Hub Centric vs. Lug Centric center bore

In case a driver does not know, there are two different types of hub bores - hub-centric and lug-centric. Hub-centric wheels have a pilot hole in the center that is the same size as your vehicle's hub. This allows the wheel to be centered on the hub before the lugs are tightened. Lug-centric wheels do not have a pilot hole and rely on the lug nuts to center the wheel on the hub.

Is one better than the other? That is up for debate. Some say that lug-centric wheels are more likely to come loose because they rely on the lug nuts to keep them in place. Others say that hub-centric wheels are more likely to become unbalanced because they are not held in place by the lugs. Ultimately, it is up to the driver to decide which type of wheel they prefer.

The hub-centric design is used most often in automotive applications because it better resists impact loads common to driving on typical roads. The alternative, lug-centric designs are less expensive and sufficient for lower-speed or lower-impact uses.

At the same time, note, that the majority of aftermarket wheels are lug-centric, meaning that their center bores fit a variety of vehicles. The lug holes on the wheel are drilled at an angle (60 degrees), so the lug nuts also have this same angled design.

The relation between wheel center bore and hub diameter

Hub diameter is a measurement of the central hole of a wheel that it mounts onto the vehicle. A smaller hub diameter leaves more room for bigger brakes, while a larger hub diameter is stronger. The most common hub diameters are 72.6mm, 66.1mm, and 54.1mm. So, if your car has a hub diameter of 72.6mm, then you need a wheel with a hub bore of 72.6mm.

What are hub-centric rings (spigot rings)?

In case you heard of spigot rings and wondered what they are, here is the explanation. Hub-centric rings, also known as spigot rings, are used to adapt a wheel with a larger bore to a smaller hub. In other words, they fill the gap between the hub and the wheel.

Spigot rings are made of different materials, such as aluminum, steel, or plastic. There are two main types of hub-centric rings:

  • those that go inside the wheel (Type 1);
  • those that go outside the wheel (Type 2).

So, hub-centric rings are sturdy and durable, made from either plastic or metal. They fit into the center bore of your wheel so that it can be mounted correctly and safely onto your car. Without spigot rings, wheels can be attached improperly to cars which often leads to vibrating or unstable wheels. Also, when these rings are selected improperly, they may damage the wheel or the car because of the friction and heat that is produced.

How do you measure hub-centric ring size?

In order to measure hub-centric ring size, you need to know the inner and outer diameters of the ring. The outer diameter is the measurement of the ring where it sits on the wheel. The inner diameter is the measurement of the hole in the center of the ring.

In order to find out what size you need, first, measure the distance across the hub where the wheel attaches. Then, look up the specifications for your car to find the correct size. You can also ask a professional at a tire or automotive shop for help.

Thus, the hub-centric ring is placed between your wheel bore and hub. For example, if the diameter of the wheel hub is 67.1 mm, and the wheel center bore is 73 mm, a centric ring with an I.D. of 67.1 mm and O.D. of 73 mm would be needed to fill that space in between. So for this application, you would need part number TOC73-6710 which is deciphered as:

  • TOC - type of centric ring (Type outside clip)
  • 73 - hub diameter in millimeters
  • 6710 - inside diameter in tenths of a millimeter

As you can see, there are a lot of different sizes and types of hub-centric rings. It is important to make sure that you select the correct ones for your car and your wheels. Failure to do so could result in damage to your car or your wheels.

To sum up, knowing the hub bore size of your wheel is important when choosing spacers or rings. It's also helpful to know the difference between hub-centric and lug-centric wheels. Ultimately, it is up to the driver to decide which type of wheel they prefer. The fitting spigot rings will make sure that your wheel is mounted correctly and safely.

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