What Is Centre Bore on Alloy Wheels?
When you're choosing new alloy wheels, you'll often see specifications such as PCD, ET, width and centre bore.
PCD and ET get most of the attention, but centre bore is just as important when it comes to getting the correct wheel fitment.
At OMI Alloy Wheels, it's one of the measurements we consider when matching aftermarket wheels to a vehicle.
So, what exactly is centre bore, and what happens if it's different from your car's hub?
What Does Centre Bore Mean?
The centre bore is the circular hole in the middle of an alloy wheel.
It is designed to locate over the raised section of the vehicle's wheel hub.
When the wheel's centre bore matches the vehicle's hub correctly, the wheel is hub-centric.
In simple terms, think of the centre bore as the part that helps the wheel locate correctly onto the car.
Why Is Centre Bore Important?
The wheel needs to sit correctly and centrally on the vehicle.
If the wheel's centre bore is too small, it won't fit over the vehicle's hub.
If the wheel's centre bore is larger than the vehicle's hub, the wheel can potentially be used with the appropriate spigot ring or hub-centric ring to fill the gap and correctly centre the wheel.
This is particularly common with aftermarket wheels because manufacturers may use a larger centre bore so that the same wheel can be used across multiple vehicle applications.
What Is a Spigot Ring?
A spigot ring, also known as a hub-centric ring or centre ring, is a small ring that fits between the wheel's centre bore and the vehicle's hub.
For example, imagine:
Wheel centre bore: 72.6mm
Vehicle hub: 66.1mm
A correctly sized spigot ring can fill that difference so the wheel is properly located on the hub.
The size of a spigot ring is normally given as the outer diameter × inner diameter, corresponding to the wheel bore and vehicle hub.
Do All Alloy Wheels Need Spigot Rings?
No.
If the wheel is designed specifically for the vehicle and the centre bore matches the hub, you don't need a spigot ring.
However, if you're using a multi-fitment aftermarket wheel with a larger centre bore, the appropriate ring may be required.
The important thing is to check the actual specifications of the wheel and vehicle rather than assuming one is needed.
What Happens If the Centre Bore Is Too Small?
This is straightforward:
The wheel won't fit over the hub.
You can't simply force the wheel onto the vehicle.
The wheel's centre bore must be large enough to accommodate the vehicle's hub.
A centre bore that is too small means you need a different wheel or an appropriately engineered solution — it's not something to ignore.
What Happens If the Centre Bore Is Too Large?
If the wheel has a larger centre bore than the vehicle hub, the wheel isn't automatically useless.
This is where a suitable spigot ring can be used to reduce the gap and help centre the wheel correctly.
Without the correct centring arrangement, some aftermarket setups can experience vibration, particularly at higher speeds.
It's therefore important that the wheel is correctly centred and properly balanced.
Is Centre Bore the Same as PCD?
No.
They're two completely different measurements.
PCD describes the wheel's mounting-hole pattern.
Centre bore describes the diameter of the hole in the middle of the wheel.
For example, a wheel specification might look like:
19x8.5 ET45 5x112 66.6
This could mean:
- 19 = wheel diameter
- 8.5 = wheel width
- ET45 = offset
- 5x112 = PCD
- 66.6mm = centre bore
You need to consider the whole specification, not just one measurement.
Can Two Wheels With the Same PCD Have Different Centre Bores?
Absolutely.
This is another reason why wheel fitment can be confusing.
Two wheels might both be:
19-inch
and both have:
5x112 PCD
but have different centre bores.
That doesn't necessarily mean one is wrong — aftermarket wheels can be designed with larger multi-fitment bores and used with the correct spigot rings where appropriate.
Does Centre Bore Affect the Price of Alloy Wheels?
Generally, centre bore isn't one of the main reasons one wheel costs significantly more than another.
The biggest factors we see affecting alloy wheel prices are things such as:
- Size
- Design
- Brand
- Finish
- Manufacturing method
- Construction
For example, our OEM-style wheels can start around £130 per wheel for 17-inch, £140 for 18-inch and £150 for 19-inch, including VAT.
Premium flow-formed wheels can cost considerably more, while fully forged wheels can reach around £3,000 for a set of four.
The difference comes down to much more than the centre bore.
Why You Shouldn't Guess Your Wheel Fitment
This is probably the most important takeaway.
When you're buying aftermarket wheels, don't just search:
“19-inch wheels for my car.”
You need to establish the complete fitment.
That means checking:
- Wheel diameter
- Wheel width
- PCD
- ET/offset
- Centre bore
- Brake clearance
- Suitable tyre size
- Correct wheel nuts or bolts
If you're unsure, it's much better to ask someone who understands wheel fitment than to buy a set and discover afterwards that something isn't correct.
How Can OMI Help Me Choose the Right Wheels?
This is where we try to make things easy for customers.
Send us a picture of your car.
Tell us:
- What size you're interested in
- What colour you want
- Whether there's a particular design you like
We can then help you find suitable wheels rather than expecting you to understand every technical specification yourself.
And if you're looking at a particular wheel, we can help you understand the fitment and what else you'll need.
Final Thoughts
Centre bore might seem like a small measurement, but it's an important part of choosing the correct alloy wheel.
Remember:
PCD tells you the bolt pattern.
ET tells you the offset.
Centre bore tells you how the wheel locates onto the vehicle hub.
All three — along with wheel diameter and width — need to work together.
And if you're buying aftermarket wheels with a larger centre bore, the correct spigot ring may be required to ensure the wheel is properly centred.
If you're unsure what wheels will fit your car, send OMI a picture of the vehicle and tell us what size and colour you're looking for.
We'll help you find the right designs and fitment.