Wheel Interchange Glossary
This is the WheelInterchange glossary for wheel fitment, wheel interchange, bolt patterns, wheel dimensions, hub dimensions, lug hardware, tire fitment, wheel adapters, spacers, and compatibility terminology. Entries are published gradually.
B
- Bolt Pattern
A bolt pattern, also called PCD or lug pattern, identifies the number of wheel fasteners and the diameter of the circle passing through their centers. It is commonly written in a format such as 5x114.3.
C
- Center Bore
Center bore, also called the wheel bore or center hole, is the diameter of the hole through the middle of a wheel. It is measured in millimeters and must be large enough to clear the vehicle’s hub.
D
- Daily Click Aggregate
A Daily Click Aggregate is a day-level summary of product-click events grouped by dimensions such as source page, tag, product, or product type. It shows how many clicks were recorded for each grouping on a given date.
- Direct Fit
Direct Fit means a wheel can mount on the target vehicle without an adapter, hub ring, or spacer, based on the available fitment evidence. It is also called a direct mount, but it still requires the wheel’s full fitment to be correct.
- Donor Vehicle
A donor vehicle is the vehicle from which a wheel, tire package, or wheel specification originates. In wheel interchange, its dimensions are compared with those of the target vehicle to determine compatibility.
H
- Hub-Centric Ring
A hub-centric ring, also called a hub ring or spigot ring, fits inside a wheel’s larger center bore to match the smaller hub pilot on the vehicle. It helps center the wheel on the hub during installation and operation.
T
- Tire Size
Tire size is a standardized designation that describes a tire’s section width, aspect ratio, internal construction, and the wheel diameter it fits. A marking such as 275/65R18 provides key dimensions for evaluating tire and wheel fitment.
W
- Wheel Adapter
A wheel adapter, also called a bolt-pattern adapter, is a component that changes the wheel-side mounting interface so a wheel with a different bolt pattern or PCD can be mounted to a vehicle hub. It can make an otherwise incompatible wheel usable, but it adds thickness and requires careful checking of hardware, clearance, and load suitability.
- Wheel Offset
Wheel offset is the distance in millimeters between a wheel’s centerline and its hub mounting surface. It determines how far the wheel sits inward or outward relative to the vehicle hub and is commonly marked as ET.