Dear Tom and Ray:

Something that looks like black soot forms on my wheels -- especially the
front ones. I own a '96 Jeep Grand Cherokee Limited with 16-inch polished
aluminum gold-painted accent wheels. They are sort of "waffle-style," with
lots of cracks and crevices for this stuff to stick between, which makes
them a real challenge to clean.
My wife has a '95 Honda Accord with fancy aluminum wheels, and it has the
same problem. How come I don't remember seeing cars with this problem years
ago? Is this because of the materials that they're making brakes out of
now? -- Guan

TOM: It's brake dust, Guan. And it's not a new phenomenon. The reason you
see more of it now is because of all those fancy "waffle style" wheels on
the road.

RAY: Most cars used to have wheel covers, which kept the brake dust
contained and out of sight. But wheel covers have fallen out of fashion.
And now alloy wheels with slots and spokes and holes are all the rage, not
only because people think they look nice, but because they weigh less and
let more air in, which provides better cooling for the brakes. The downside
is that those same holes which let air in, let brake dust out.

TOM: The stuff is harmless, Guan. At least to your car. I mean, I wouldn't
sprinkle any on your corn flakes or anything. But aside from the all-
important aesthetic considerations, it's nothing to worry about.