Knowledge Base / Wheel Fitment Guide
How to Read PCD, ET and Center Bore
Three numbers decide whether a wheel bolts on, sits right, and centres without shaking. Here is what each one actually does.
Three numbers decide whether a wheel bolts on, sits right, and centres without shaking. Here is what each one actually does.
PCD (pitch circle diameter) is the diameter of the circle the bolt holes sit on, plus the number of holes: 5×112 means five holes on a 112 mm circle.
It is the one number you cannot fix. Adapter plates exist, but they add width and load path you did not design for. If the PCD is wrong, the answer is a different wheel.
Offset is the distance from the hub mounting face to the wheel's centre line, in millimetres. Positive sits inboard, negative sticks out.
Two wheels of the same width and different ET sit differently: lower ET pushes the wheel outward. That changes arch clearance outside, strut clearance inside, and scrub radius — which is why an offset copied from a forum post on a different trim can rub.
The bore is the hole in the middle of the wheel that sits on the hub spigot. If it is larger than the hub, the wheel is located by the bolts alone — that is what centring rings try to mask.
We cut the bore to the hub. It costs nothing at the drawing stage and removes a whole category of vibration.
Read the numbers stamped on the inside of an OEM wheel, or look up the vehicle's specification.
Then tell us the car, the year and the brakes. We confirm the rest before anything is cut.