As others have noted the wheel needs to come off, the cap installed, and the
wheel and cap re-installed together. Now to be sure were are talking about
the rear! The rear brakes make little dust and what dust that does escape
will come out the back of the drum. Dust also wipes off unless left on long
enough for the corrosive effects to damage the finish.

The staining is more likely due to grease or maybe even brake fluid. Take a
good look at the axle nut. Is it wet? If so that is your problem. The grease
is working it's way out of the bearings due to combination of being over
greased or it is breaking down. Worse though if it is working out from
between the nut and the hub that is an indication the hub-nut assembly is
loose of the face of the hub is worn allowing the space for the grease-oil
to work out. This needs to be addressed as a loose hub will eventually cause
other problems including the spline failure leaving you stranded.

Now for cleaning the wheel there a number of wheel cleaners that work very
well. Auto cleaner-waxes also work very well. Keeping the wheels waxed make
future cleaning real easy.

Dennis

-----Original Message-----
From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf Of
David M
Sent: Saturday, March 30, 2013 4:10 PM
To: vanagon@GERRY.VANAGON.COM
Subject: Brake dust on alloy wheel ?

I have the 14in VW alloy wheels on my 1987. A few weeks ago I had a rear
tire changed and when the shop did it they omitted to reinstall the plastic
center cap. Since I could not figure out how to re-install it, I just left
it off and did not think twice about it. When filling up for gas, I now
noticed that that alloy wheel (and none of the other three) is covered in
blackish gray stain. I'm assuming this is brake dust? Does the center cap
really prevent this or is it just a concidence? And just how to I get this
wheel looking shiny aluminum again. I tried using toothpaste and it had
little effect. How do I reinstall the center cap? Thanks.

-David (1987 Wolfsburg GL, Tempe AZ)