I have a good one for you My house-mate took...

Dear Car Talk

Dear Car Talk | Jul 01, 2002

Dear Tom and Ray:

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: Geez, 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 bullet-proof 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 it was eventually 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.

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