I have a 99 A6 and recently had to replace a cracked rim (the "wineglass" 9-spoke one). I found a used one that is possibly the dirtiest wheel I have ever seen. I have used a DuPont product that typically works for regular wheel cleaning but barely made a difference on this one. I wanted to get some advice from everyone before I try every wheel cleaning product on the shelf. Any thoughts or tips are greatly appreciated!

 

I am not familiar with the wheel you are describing but imagine that it is clear coated like most factory wheels have been for the past 20 years.

I would try some household detergents myself, even if possible soak the wheel for a period of time. If it is as bad as you say each cleaning pass will take off another layer and you will eventually see results. Made sure once it is clean to apply a good layer of wax to make future cleaning easier. If the build up is oily in anyway use some solvent sparingly as a last resort.

 

Heavily soiled - The front wheels are usually more soiled, as this is where most of the vehicle braking effectiveness is. For badly soiled surfaces use an undiluted citrus-based APC (P21S Total Auto Wash) let it dwell for 5-10 minutes and then use a very Fine Grade synthetic brass wool, do not use heavy pressure, then use detailer’s clay followed by a gel-type wheel surface cleaner (P21S Wheel Cleaner) apply a polymer surface protection to ensure easier future cleaning (Klasse All-In-One or ZoopSeal) (http://www.autogeek.net)

Sequestered metal brake dust, if left for any length of time on the wheels causes galvanic corrosion, which etches the surface and eventually dulls the wheel’s appearance if not removed on a regular basis. To remove brake dust stains use a mildly abrasive cleaner (Iz™ einszett Metal Polish “Chrompflege”, P21S Multi-Surface Finish or Autosol)