Alloy wheels are much lighter than metal wheels or rims. High-performance alloy wheels are stronger than metal wheels in a blend of aluminium and other more rigid materials. This type of wheel is generally wider and taller than a standard metal wheel that is stock mounted on a vehicle. This allows less thickness of the tire sidewall and improves the handling of a vehicle while maintaining the same rolling ratio.
Set the wheel on a flat surface on the rim so it sits in the same position as when it is mounted on a vehicle.
Place the tip of a measuring tape from the top bead set area to the bottom bead set area on the outside of the wheel. The bead set area is where the tire sits inside the wheel and does not include the outer edge of the wheel. This is the diameter of the wheel.
Place the measuring tape tip across the width of the wheel, and measure from the bead set on one side to the bead set on the other side. This is the area where the tire fills the wheel in width not including the outer edges of the wheel. This is the wheel width.
Lay the wheel flat on the surface with the lug nut holes facing up. Count the number of lug nut holes in the rim.
Measure the lug nut pattern on an even-numbered wheel from the centre of one hole to the centre of the hole directly across from it.
Measure the lug nut pattern on an odd-numbered wheel from the centre of one hole to the back of the hole that is two holes away in either direction from the first hole.
Use the diameter and width measurements to purchase a tire to fit the alloy wheel. Use the lug nut pattern to compare to a vehicle's lug nut pattern and size to fit the alloy wheel.