Clutches, Brakes Wear Out Faster

Question: I have just replaced my clutch after only 28,000 miles. My mechanic told me that clutch discs no longer contain asbestos and are not lasting as long. Is this true?--P.M.

Question: I own a 1986 Nissan Pulsar with 36,000 miles on it and I am on my third clutch. The Nissan dealer says nothing is wrong, but I have to pay for it each time. I wonder if others are having the same problem.--S.M.

Question: I have just gone through a set of brakes after only 15,000 miles. What gives?--J.N.

Answer: The reliable clutches and brakes that motorists had come to expect are more or less a thing of the past, owing to a variety of factors. While clutches and brakes can still be quite good and can last a very long time, they can just as easily can be a maintenance nightmare.

One of the leading causes of reduced brake and clutch performance is the downsizing of brakes and clutches by manufacturers, in an effort to save space and weight. A small clutch or brake must still perform the same amount of work, so it simply wears out more quickly.

In the past, for example, clutch discs were 11 inches or more in diameter; some were as large as 16 inches. Today, clutches are more likely to be 10.5 inches. That puts more stress and heat on the clutch lining and wears it out more quickly.

Brakes have also been significantly reduced in size. In the 1970s, brake rotors were typically 12 inches in diameter. Today, they are 9.5 inches. The same thing has happened to drums. The Ford Escort underwent a substantial reduction in the size of its drum.

In the past, brakes would often last 50,000 miles. Today, brakes may wear out at 20,000 to 25,000 miles. Presumably, these cars get better gas mileage and are saving motorists money in that area, but when you are facing a stiff brake repair bill, it is easy to forget the small amounts you save weekly on gas.

Brakes and clutches work on the same principle. A clutch consists of a disk--with friction material on each side--that is pressed between the flywheel and a pressure plate. When the pressure plate is pulled away, the clutch disk floats away from the flywheel and disconnects the engine from the transmission. Brakes work with two friction pads that squeeze against a metal disk to create friction and stop a car.

It is true that asbestos, the material that has long been used for clutch plates and brake pads, is being phased out. Asbestos is a cause of cancer and poses a significant health risk to mechanics who change brakes every day. Under federal regulations, production of asbestos brakes and clutch linings will be eliminated by 1993, the use of asbestos linings by car manufacturers will be eliminated by 1995, and all automotive use of asbestos will be outlawed in 1997.

But asbestos can be replaced with newer materials, which may hold up longer than asbestos; these brakes are often referred to as organic brakes, although they generally do include some asbestos. There are also semimetallic brakes, which do not contain asbestos and are quite hard and capable of longer wear than brakes containing asbestos, though they cost more.

One problem with semimetallic clutches and brakes, however, is that they tend to require greater care. For example, newer disk brakes have low drag calipers, in which the brake pads are retracted fully away from the brake disc.