You can also get something like the "California Duster" (bought mine from local Wal Mart). I use it on my wheels every other day (or whenever the rims look dirty) and they keep them looking pretty clean (and a whole lot easier to clean when the car is washed). It is kinda hard using them on the 214's (my wife's 3 series 5 spoke are a breeze to wipe down), but they definitely help.

Used PS21 (both regular and gel) in the past. I wasn't that impressed with it. I did an equally good job with just using the left over soap water from washing the body of the car.

Just bought and received Chemical Guys "Wheel and Rim Cleaner Gel". Can't wait to try it out this weekend to see how it works.

On a side note:
After reading various detailing forums, I Rejexed my rims when I first got them (think it pretty much does the same thing as the Klasse). On 2 rims, I didn't apply the Rejex to the inside of the rim, while on the other 2 rims, I did. Everytime I wash, I only do the outside as I find it very difficult to clean the inside section (just ordered a few tools to see if I can retify that situation). So after 14,000 miles and about a year +, I'm tried cleaning in extremely dirty inside part of the rim. Rejex does seem to work in making it easier to clean (practically clean with just plain soap water). The non rejexed rims had more of the brake dust stuck on it (after the soap water). I'm sure a good degreaser would get that out.

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2008 X5 4.8
White w/ Black Interior w/ Bamboo Trim | Premium | Sports + 214" | Tech | Cold Weather | Rear Climate | Premium Sound | Active Vent Seats | Heads-Up | Comfort Access | 3rd Row | Aero Kit | Huper Optik Tint | Clear Reflectors