Question: I have a good one for you. My house-mate took her car into the shop for new brakes because hers had started to grind. The mechanic replaced her brakes. About a week later, the brakes started to make noise again. She took the car back. Then it happened again. The third time she took the car back to him, he took off a wheel and showed her the brake pads.
"See these specks of gold?" he asked. "They're rubbing on the rotors and making the noise. We have to order you some pads without so much gold in them."
When she got home, she told me the story, and I said, "Bo-o-o-o-gus!" Then I thought, what do I know about brake pads? I can't see putting a low-melting-point precious metal in brake pads. So I searched a million Web sites trying to find out what brake pads are made of, and came up empty. So, guys, what are brake pads made of? — Angela
Ray: Wow, Angela. See what you've done? Before he even finished reading your letter, my brother ran out behind the shop to start panning for brake pads.
Tom: The "gold" is actually bronze and copper, Angela. And you're right. There is no gold in them thar brake pads.
Ray: Brake pads are made of an amalgam of bronze, copper, iron and steel wool, all usually held together with Kevlar — the stuff they make bulletproof vests out of — or some other bonding agent.
Tom: They used to use asbestos, which seemed like a perfect material for brake pads: It was fireproof, hard enough to last a long time and soft enough that it didn't screech. But asbestos was found to have one major disadvantage: It killed people. So eventually it was dropped in favor of this mix of metals.
Ray: The metals are hard enough to last a long time, but they do have the disadvantage of being so hard that they're noisy — especially at first, until they mate with the rotors.
Tom: So when we put them in, we make sure to drive the customer's car for a while and work the brakes to get them well on their way to being broken in.
Ray: We also turn up the radio, loosen the fan belt and remove some of the weather stripping around the doors to add some masking noises, just to make sure the brake noise doesn't bother the customer.
Tom: So your roommate has a few choices. One is to wait a few weeks until the new pads seat and see if they quiet down by then. Assuming she got some good-quality pads, like Bendix, Raybestos or Wagner, they probably will quiet down.
Ray: Another option is to go with softer pads, which you can get for some cars. That's what the mechanic has ordered. They will probably reduce the noise, too, but they might not last as long as the metallic pads.
Question:I just got the sad news that my air-conditioning condenser is gone, and it's going to cost me $900 to replace. When I told my husband, he said that I should have known that car air conditioners have to be run at least once a month throughout the year to keep the seals in good shape. Well, I DIDN'T know that! I did an informal poll at work, and no one else knew it, either. Is it true? — Jane
Tom: Well, it's sort of like what the Jewish grandmother says about chicken soup: "It couldn't hurt."
Ray: But it wouldn't have helped you, Jane. The reason you run the AC every so often in the off-season is so the moving parts of the compressor don't seize and so the seals stay soft and pliant.
Tom: But your compressor didn't fail, Jane. Your condenser did. And there's nothing in the condenser that moves. The condenser is located in front of the radiator, and it simply cools and condenses the AC's refrigerant. My guess is that some sort of roadway debris hit it and knocked a hole in it, or it just rotted out. And running the AC in the winter would have done nothing to prevent that.
Ray: Many cars automatically turn on the AC when you use the front-window defroster. And in those cars, you obviously never have to think about it, because you'll inevitably use the AC all year round. But some cars don't have that feature. And on those cars, it can't hurt to turn on the AC once a month or so during the winter.
Tom: And don't worry about freezing. You can turn the heat up full blast with the AC on. That doesn't cause any problems at all. And it'll keep you from suffering from "heiniethermia."
The Magliozzi brothers' radio show, "Car Talk," can be heard Saturdays at 10 a.m. and Sundays at noon on KUER FM 90.1, and on KCPW 88.3/105.1 FM Saturdays at 9 a.m. and Sundays at 10 a.m. If you have a question about cars, write to Click and Clack Talk Cars c/o King Features Syndicate, 235 E. 45th St., New York, NY 10017. You can e-mail them by visiting the Car Talk section of the Web site www.cars.com.