GIVE YOURSELF A BRAKE

Motor, Jun 2005 by Seyfert, Karl

Even something as seemingly routine as a brake job can turn into a profit-destroying comeback if just a few small steps are overlooked or incorrectly performed.

Today's high-tech world of auto repair may occasionally make you wish for a return to a simpler, less complicated time. More than once, I've heard a frustrated tech exclaim "Just give me a brake job to do once in a while and I'd be happy." Brake jobs and other basic maintenance like suspension service and tuneups were the bread & butter jobs that kept many shops in the black for generations. Indeed, entire service chains were established and flourished by catering exclusively to this type of work.

What's different now? Cars still have brake pads, shocks, struts and spark plugs. Yet hardly anyone even mentions these things anymore. Today, we seem consumed with concerns about diagnosing and repairing the electronic components that control an ever-increasing number of complicated vehicle systems. Learning how they work and how to repair them when they don't will continue to command a large percentage of our available brainpower.

If you had a brake job to do tomorrow, would you approach it with the same level of thoroughness and professionalism that you bring to other, more complicated repairs? Or would you rush through it distractedly, eager to return to the thorny diagnosis that s been occupying your thoughts for the past several hours? Too often, the second scenario leads to other unforeseen but perhaps completely avoidable problems.

This article isn't intended to show you how to do a complete brake job from start to finish. What it will do is highlight several of the small but veiy important steps that can be and often are overlooked in the rush to complete a "routine" brake job. The stuff we miss when we hurry more often than not results in an unwelcome and unprofitable comeback.

What follows is a short list of complaints that are sure to bring a customer back to your shop following a brake service. After we've identified the problems, we'll consider the steps that can be taken to cancel them out before the car leaves your shop.

Brake Squeal, Squeaks And Other Noises

One of the most annoying noises that any vehicle is capable of making is a high-pitched squeal or squeak when the brakes are applied. The squeal provides the driver with an audible cue that something isn't right, and may in fact be terribly wrong. And nothing will bring a customer back to your shop faster following a brake service, especially if the brakes didn't squeal before you worked on the car. An explanation that "they all do that" just isn't going to fly.

It's true that some brake noise is normal and, to a certain extent, unavoidable. But there are a number of small and reasonably simple things you can do to prevent abnormal brake noise.

First, examine the shims in place on the vehicle's original brake pads. They've already been subjected to a great deal of heat and may also be deterioriated due to exposure to the elements. If they look questionable, replace them. If you don't, you're inviting brake noise.

It may also be necessary to insulate the brake pad from the caliper with a spray or paste coating. The backs of the pads are coated prior to installation and this coating serves as a layer between the pad and caliper. Follow all manufacturer directions on where to apply and curing times. Many brake systems use a sandwich of materials (a shim) that's staked to the back of the pad. Pressure-sensitive adhesives may be used to secure the shim to the pad's backing plate. Clips may also be used to clamp the shim.

The type and quality of the brake pad material you install also can have an effect on brake noise complaints. Always use the recommended friction material when replacing brake pads and shoes. Using the incorrect type of material can cause noise and can affect the stopping ability of the vehicle.

The friction material used for pads and shoes can be identified by a code printed on the edge of the lining. This code identifies the manufacturer, the material and the cold and hot coefficients of friction. It does not indicate lining quality or hardness. When troubleshooting a brake problem, it's often a good idea to install new brake linings that match the OE friction specifications.

Carmakers may also specify different friction materials for the inboard and outboard pads, such as an organic pad on one side of the caliper and a semimetallic pad on the other. It's also common to see linings with a lower coefficient of friction on the rear brakes than on the front to minimize rear brake lockup, particularly on front-drive cars.

Noises other than squeals or squeaks, such as rattles or clunks, may have other causes, which will be covered in greater detail later.

Brake Pulsation

Brake noise and brake pedal pulsation often go hand in hand because they may have similar, related causes. On disc brake-equipped vehicles, brake pedal pulsation is caused by rotor thickness variation. As the brake pads attempt to follow this variation, brake noise may also result. Pedal pulsation can also be caused by machining variations on brake drums.