Different Types of Polished Wheel Finishes
There are several different types of polished wheels out there; traditional, machine-polished and brushed. All are based on some technique of buffing the metal of the wheel to a high shine, but the methods, the results, and the necessary care and maintenance differ widely.
Along the spectrums of beautiful finish, durable finish and easy-to-care-for finish, polishing tends to straddle the gap between painted wheels and chrome supermodels. The advent of clearcoat for polished wheels especially has mostly turned these finishes from maintenance monsters into acceptable housepets.
Traditional, or ball polishing is applied by buffing the wheel, usually with progressively softer materials until the metal achieves a deep metallic glow. Older polished wheels were generally not clear coated, as it took a while to develop a clearcoat that could adhere properly to the extremely smooth polished surface. Polished wheels without a clearcoat would have to be washed, dried and waxed, usually every week, to keep air and water from corroding the metal. Even with all that many owners would find it necessary to do some repolishing with a ball polisher and fine compound every once in a while.
Lately, however, nearly all new polished wheels have a clearcoat, making possible some configurations that probably would not have been attempted back in the day. Many 3-piece wheels, for example, now sport polished lips that would have been nearly impossible to wax.
Repairing a polished finish is relatively simple, if generally somewhat expensive, as it must be repolished by hand. Fortunately, older polished wheels can now be clear coated after being repaired.
A machined finish is applied by spinning the wheel on a Computer Numeric Control (CNC) lathe. The lathe bit cuts a small amount of metal off the face of the wheel, flattening and polishing the surface to a high metallic shine. This process leaves tiny concentric lines in the finish, giving it an effect somewhat like the surface of a CD.
Most often, the wheel is painted a contrasting color before being lathed. The lathe polishes the high spots in the wheel while leaving paint in the low spots, an effect we call “paint in the pockets.” Or the lathe might only cut the outer flange and leave paint in the center of the wheel, called a “flange cut.”
Machined finishes can be repaired by putting them back on the CNC lathe – up to a point. Because the lathe operates by removing material, there obviously has to be enough material to remove. Repeated lathings will eventually reach a point where there is simply not enough metal left to safely refinish the wheel. Certain wheels with flanges that are thin, to begin with, may also be unsafe to lathe.
Several wheel makers, perhaps most notably TSW, have begun using a specialized machining process that TSW calls “Diamond Cut” in which the lathing is done at higher speed with a diamond-coated bit which produces a smooth, line-free finish that looks much like traditional ball polishing. It’s a beautiful finish, but it’s very difficult to repair due to the specialized equipment.
In 2009, Borbet debuted a new type of polished finish called “Borbet Brushed.” Using a hush-hush process that apparently involves brushing the metal surface in various ways, Borbet achieved a highly dimensional effect that could be varied to embed interesting patterns in the finish. However, since debuting at a German wheel show and sponsoring a wheel design contest, the finish has essentially dropped into a black hole and has never become available outside Europe. Borbet tells me that the finish was largely a casualty of the global recession and consequent collapse of the tuner market and that they intend to reintroduce the finish when economic conditions are better.
Whatever the type of polish, if it is clear coated, the wheel should be cleaned with a mild, non-acid, non-abrasive cleaner such as Simple Green and water.