Wheel Composition & Finish

Wheel Composition

Until recently, stock wheels were typically steel, a strong, durable material which is easily repaired. However, more and more new vehicles are equipped with aluminum alloy wheels by their manufacturers. Alloy wheels are extremely popular because of their appearance, and they also run cooler than steel wheels, due to the superior thermal conductivity of aluminum. 

Steel wheels are made from two pieces, a center and a barrel, and these are welded together around the inner diameter of the barrel. Steel wheels are typically painted black or silver, but for an improved appearance, they can also be chrome plated. These are known as chrome wheels or “chrome rims.”
Aluminum alloy wheels are available in a multitude of designs and are made using one of several different manufacturing methods. The first method for making these wheels involves a casting process in which melted aluminum alloy is poured or injected into a mold.  After the metal cools, these wheels are then machined to provide better balance and a smoother, more aesthetically pleasing surface. Afterwards, they will be sprayed with a clear or metallic coating coating. Several different casting processes allow wheel manufacturers to fill the mold with varying levels of casting pressure. Higher pressure processes are more costly, but they produce a wheel with superior strength. These wheels are sometimes specified with designators like HCM (high counter pressure), and they represent a premium quality product.

Billet wheels are another popular type of alloy wheel, which has been made possible by huge specialized machines, which are able to exert huge amounts of pressure to squeeze and roll a solid billet of aluminum alloy into the shape of a wheel. Also known as forged wheels, the alloy in these wheels has a stronger grain structure than cast alloy wheels, which allows them to have thinner and lighter profiles. Because the current trend has been moving towards much larger wheel sizes, forging permits much lighter wheels for these larger sizes, resulting in lower unsprung weight and better suspension characteristics and better handling during extreme steering maneuvers. 

Sometimes alloy wheels are made using a combination of casting and forging. This may involve a cast inner wheel and a forged barrel which are attached together by forging or with a circle of decorative rivets.  

Wheel Finish

Many different types of finishes are applied to wheels, including painted surfaces, clear coats, machined and polished finishes, and plated finishes. While the most common paint color is black, painted surfaces may also be silver, gunmetal, platinum, aluminum, two-toned, and paint may also match a particular vehicle’s body color. 'Machined' refers to the surface of alloy wheels which are finished using large milling machines and lathes. In some cases, these machined surfaces are ground and polished. Alloy wheels are even available with chrome plated finishes. Chrome actually begins with copper plating, followed by a plated layer of nickel. Besides the bright chrome which is most common, custom plating colors like “black chrome” are also available, as is gold plating.