Q. Dear Tom and Ray:

What can be done about brake dust? It gets all over wheel rims and tires and streaks with black smudges when the dust gets wet. Someone suggested little plastic discs that go between the brakes and the wheels, but I'm afraid to use these because they probably reduce the airflow to the brakes. Any thoughts?

-- Henry

A. TOM: Brake dust is one of the great scourges of the late 20th century, Henry. It's like malaria was in the late 19th century.

RAY: Or those hideous powdered wigs in the late 18th century.

TOM: For those of you who have never heard of brake dust, it's just the natural powdered residue that comes off the brake pads as they get worn down.

RAY: On certain cars, because of the design of the wheel and the airflow around the brakes, that dust ends up all over your nice, expensive alloy wheels. My wife drives a Volvo, and the brake dust on that car is terrible. Unless you're willing to wash your wheels once a week, there's not much you can do about it.

TOM: You can buy some special goop that's designed to clean the dust off alloy wheels, but according to my brother even that stuff doesn't do Jack.

RAY: Nope. The dust just bounces off of it, like bullets off Superman.

TOM: And you're right not to use the dust deflectors, because they do trap heat and could cause your discs to warp.

RAY: So we don't have a good solution for brake dust, Henry (as you've doubtlessly already noticed). I'm thinking about just painting my wife's alloy wheels black. That won't do anything to stop the dust, but at least it'll hide it better, and I won't have to look at it.

Dear Tom and Ray:

I have a '94 Honda Accord station wagon. Last year, I stalled because the brake pedal became hard and slowed the car to where I couldn't keep driving. While I waited for a tow, the brake pedal came back to normal. It happened again recently, and this time smoke was coming out of the brake. The mechanic told me it's the caliper. Another mechanic told me there is no problem with my caliper. Again, the car returned to normal after two hours. What do you think is the problem?

-- Tito

RAY: Well, if mechanic No. 2 actually inspected the calipers and determined that the slides and pistons are all moving freely and easily, then he's probably right--it's unlikely to be a caliper problem.

TOM: Plus, a bad caliper won't make the pedal get hard.

RAY: So I'd suspect the power-brake booster. The booster is a device that provides the boost, or "power," to your power brakes. It multiplies the effort of your foot on the brake pedal and applies that force to the piston of the master cylinder.

TOM: If the booster is faulty, it could provide pressure to the brakes even when your foot is off the pedal. The result would be that it would seem as if you were stepping on the brakes even when you weren't.

RAY: Here's how you test it. Next time you experience this condition, pull over and yank your Sears 16,598-piece tool kit out of the trunk. Or grab a pair of locking pliers. Unbolt the brake master cylinder from the booster. If brake pressure is immediately released and the car moves freely, then your problem is the booster.

TOM: If separating the booster from the master cylinder does not solve the problem, then you may have a faulty master cylinder.

RAY: But assuming your mechanic has accurately inspected the caliper, I'd put money on the booster, Tito.

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(C) 1999 by Tom and Ray Magliozzi and Doug Berman