3-Piece Custom Forged Wheels Construction Explained
Custom fitting 3-piece wheels may seem daunting at first, but by taking the time to get the right measurements, you can take most of the guess work out with confidence knowing your new wheels will fit as you envision.
Below we review some of the terms involved when building 3-piece wheels and provide a detailed diagram for you to follow:
Wheel Diameter (D) – Usually measured in inches, this is the specified measurement of the diameter of the wheel.
Wheel Width (W) – Also measured in inches, this measurement determines the width of the wheel from the bead of the outer lip to the bead of the inner barrel.
Pitch Circle Diameter (PCD) – The bolt pattern and diameter of the circle that passes through the center of each bolt position. In the example 5×112, “5” represents the number of bolts and “112” is the diameter in millimeters.
Centerbore (CB) – The diameter, usually measured in millimeters, of the hole in the center of the wheel that mounts to the hub of vehicle. If the centerbore matches the measurement of the hub, this is referred to as hubcentric. If the centerbore is greater than the measurement of the hub, then you will require “hubcentric rings” in order for proper fitment.
Centerline – This is the exact center of the wheel that divides the width of the wheel evenly.
Offset (+/-) – Measured in millimeters, this measurement can be either positive or negative. It is the measurement from the hub mounting surface to the wheels centerline. Negative offset will push the wheel face out towards the fender. Positive offset will pull the wheel face inward away from the fender.
Center Load – On a 3-piece wheel, you have the Lip, the barrel and the face of the wheel. Center load is where the face of the wheel is sandwiched between the lip and the barrel of the wheel.
Front Load – On a 3-piece wheel, front load is when the face of the wheel is mounted in front of the lip and barrel of the wheel
Outer Size (OS) – This measurement is the size of the LIP of the wheel on a 3-piece wheel.
Inner Size (IS) – This measurement is the size of the BARREL of the wheel on a 3-piece wheel.
Backspacing (BS) – This measurement is taken from the mounting surface of the wheel to the inner part of the wheel. This measurement determines the clearance of any suspension parts of the vehicle from the wheel barrel.
Backpad (BP) – This measures the thickness of metal behind the face where the wheel mounts to the hub. This specification determines clearance for the brake calipers.
Wheel Profile – This is the flatness of the wheel face. Normal being completely flat, concave having a negative convex of the surface of the face of the wheel and deep-concave having an even more pronounced negative convex surface of the face of the wheel.