The Chrome Shadow Paint Process: BMW was among the first manufacturer to use this paint finish starting way back in 1998-1999. The alloy wheel is initially powder coated black and then baked under heat to allow it to flow and form a “skin like” base layer that is very durable. Once fully cured, a super thin layer of silver (chrome shadow) paint is sprayed over the powder coat base. The silver paint used by BMW comes from a company in Italy called Color DEC and is a lead based paint. Finally, a thin clear coat is applied as a final measure. The end result is a three-dimensional finish with a nice depth; one of the more striking features of the E39 M5.
Differences in OEM Finish: One of the difficult, if not down right annoying aspects of the chrome shadow line of wheels for the E39 M5 are known differences in the appearance of OEM factory wheels. Because the chrome shadow paint is sprayed in such thin layers it’s possible for there to be differences in shade depending on the technician performing the work at the factory. As an end result, there are entire batches of wheels that will come out slightly darker or lighter. The following pictures are both OEM wheels; the wheel on the left is the original that came on the car and one on the right was sourced 3-years ago through Bavarian Autosport.
Wheel Refinishing: With in the last 5-years several refurb operations from mobile to specialty shops have been offering refinishing services for the chrome shadow wheels. The quality of the end result has improved noticeably over that time. Many share the opinion that a good operation can produce a finish that is almost exact to the factory (98-99%) with some reporting a 100% perfect match. There are a couple of key issues to understand with regards to refinishing a wheel. The most accurate refinished wheels use a process that mirrors that of the factory; powder coated base followed by silver paint and clear coat layers. There are many shops that substitute a powder coating process for a lacquer base layer as its less time consuming and presumably less expensive. Furthermore, since the original chrome shadow paint used by BMW is lead based it’s illegal for it to be used in many areas (but not everywhere) in the U.S.A. As stated by Jclyman:
"The lead content issue is more interesting, though. It seems that lead paints are legal in some places here, but not in every jurisdiction. In Los Angeles, for example, definitely NOT allowed to be sold. It seems to vary. Not even regulated by the particularly county involved. Hit and miss, if you will. I expect that since the Shadow Chrome paint maker couldn't control where the paint WOULD be sold, it was easier NOT to import in here, at all. PPG (a major automotive paint producer) still sells lead based paints for sale to body shops in some places."
This means that many shops are using a paint similar to the one manufactured by ColorDEC but not the same exact one.
Most operations I know of in the U.S.A. will only repaint an entire wheel and will not do spot touch ups. Furthermore, most if not all suggest having all 4 wheels refinished simultaneously to ensure an accurate match from wheel to wheel. Having said that, I saw a mobile outfit based in the U.K. on this board: Wheels refurbished today (with pics!) which was able to do spot touch ups that were apparently 100% undetectable.
Wheel Refinishing Operations: There are shops all over the country that will refinish wheels. I was initially going to list the more notable ones but the quality of the finished product is a hotly contested topic. It would seem that the general consensus indicates an improvement in accuracy of the finish over the years but rarely is a shop able to match an OEM 100%. This is not to say it can’t be done, just that it shouldn’t be an underlying expectation.
