Your rotors are softer than your brake pads. Talk about a design flaw!

Dear Car Talk

Dear Car Talk | Aug 01, 1993

Dear Tom and Ray:

I am the owner of two General Motors cars which were purchased new. They are a 1990 Pontiac Grand Am and a 1991 Buick Skylark. Both have 2.5 liter, four cylinder engines. They each have about 20,000 miles on them. Although the brake pads on both are still good, the brake action is terrible. Both cars have a high pulsating type action when the brakes are applied. My mechanic says that the rotors are pitted and need replacing. he further states that the GM car rotors for these years are "junk," and almost all of them need replacing before 30,000 miles. Shouldn't they last longer than 30,000 miles?

RAY: Yes, they should. While it is possible to wear out a set of rotors in 20,000 or 30,000 miles, you'd have to drive like a real knucklehead in order to do it (by the way, if you want specific instructions, they're in our pamphlet, Ten Ways You May Be Ruining Your Car Without Even Knowing It. You can get your own copy by sending an SASE and $3 to ...). If you're flooring the gas and slamming on the brakes all the time, you can wear them out in LESS than 20,000 miles. But you're clearly NOT doing that kind of abusive driving, John, because if you were, your pads would be all worn out, too.

TOM: And yes, it is ridiculous for a set of disc rotors to wear out before the pads do. It's like a wheel wearing out before a tire. And if the rotors are warping or getting pitted even before the pads wear out, then they were poorly manufactured, or were made of sub-standard materials.

RAY: Here's why they're having a problem. Brake pads used to be made of asbestos, which was a great material for brake pads. It was hard enough to stop the car, but soft enough so it didn't screech. There was only one little problem with turned out to cause cancer in laboratory rats and automobile mechanics. And since people felt sorry for the rats, the government banned asbestos.

TOM: So manufacturers switched to metallic brake pads, which are much harder than asbestos. They're fine for stopping the car, but squealing brakes were driving people bonkers. So next, some car makers tried making softer rotors to compensate for the harder pads. That helps with the squealing, but as you well know, John, the rotors wear out faster.

RAY: So they haven't really come up with a good solution yet. And GM isn't the only company using softer rotors. We've had some highly touted Japanese cars come into our shop for rotors at 30,000 miles, too.

TOM: So what do we suggest? Well, a letter to the manufacturer might be in order. But I think a letter along with 40 pounds of warped disc rotors would make a much stronger statement. That should remind them that they still have work to do on this problem.

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