Automotive Brakes: A Dummy's Guide

Advantage. Just a word that is pretty harmless alone, yet when a couple of other words are added with it, the situation can be in or out of a persons favor. Taking advantage of...or...taken advantage of...

Most of the times when a person is taken advantage of it is because they are ignorant or naïve to certain aspects of a situation. Hopefully this article can help a person from being taken advantage of at one of our favorite places to go...the automobile mechanic. Most of us would rather have a chipped tooth and need the services of a dentist rather than hear a noise coming from our automobile, because a dentist can show you exactly where the problem is in your mouth with an X-ray. Yet...a noise coming from a car? In most cases people have to take someone elses' word for a proper diagnosis of the problem.

In this article I will focus on one very important part of a persons vehicle, the brakes. When a person hears their brakes squealing one of the first thoughts that usually runs through their head is, "How much is this going to cost me?" A justifiable thought and the squeal you hear can come from a couple of different sources...brake pads that need to be replaced or brake pads that need to be cleaned.

Brake pads are designed with a piece of metal that is called a wear indicator. This is a piece of metal that sticks out of the pad and points somewhere near the rotor. The rotor is the round piece of metal that the brake pads squeeze against to stop the car. Usually the wear indicator will start making a chirping or squealing noise when the brake pads are worn to about 1/8 of an inch. Most pads when they are new are between 3/8 of an inch to ½ of an inch in width depending on the vehicle.

The way to tell if the noise is from worn pads or dirt is simple. Brake pads that are dirty usually only squeal when the brakes are applied...at any speed. Pads that are worn will commonly squeal at low and intermediate speeds in both reverse and forward motions. They will also squeal when coming to a stop.

Dirty brake pads are easy to clean and should be cleaned as soon as possible to avoid the risk of damaging the pads or warping the rotors. The procedure is to simply buy a spray can of brake parts cleaner (which can be found in practically any gas, convenience or department store), removing the wheel from the vehicle and spraying a generous amount of brake parts cleaner on both sides of the rotor and around the brake pads. Brake parts cleaner is not a very healthy fluid to get on skin, rubber, paint or clothes, so use caution when applying. Remember...buy brake PARTS cleaner...NOT BRAKE FLUID.

Now that I am on the subject of brake fluid, let me also say that low brake fluid in the brake fluid reservoir is another way to tell if your brake pads are worn. Brakes on most modern cars have calipers that run off of a pressure system. The calipers have pistons in them which push the pads against the rotors to stop the car. Because of the pressure and hydraulics involved in the system, the pistons do not retract much as the pads wear down. Therefore, the level of fluid in the reservoir will gradually decline as more and more of the fluid is being used to keep the pistons in the calipers in a safe relation to the size of the pad. I hope that makes sense. Just remember that the pistons are the things that push the pads against the rotor and the reason they push is because of the brake fluid. The brake fluid reservoir is a rectangular thing that is connected to a big round thing on the firewall of most cars. It is always marked as Brake Fluid and the reservoir is a somewhat clear color that makes it possible to visually see the level of the fluid.

Do not be alarmed if the fluid is low because it just means your brake pads are wearing down. DO...I repeat...DO be alarmed if your fluid level is low and your brake pedal is going all the way to the floor when you apply the brakes. It doesn't take a rocket scientist to figure out that, based on the previous paragraph, the fact that the brake system is a type of hydraulic system and that low pressure in any hydraulic system is a bad thing. If you have a brake leak...believe me...you will know it. Think of it as a garden hose with a leaky spray nozzle attached to it. The water company makes sure there is adequate water pressure for you to be able to turn your faucet on and spray water from a hose at what seems to be an infinite amount of time. But when you stop spraying the nozzle, it is the pressure of the water system that is the reason for the hose or nozzle to leak. This is sort of how a brake system in a car works. As long as there is pressure you are fine and unless you have an infinite amount of fluid in your car, you can see how noticeable a small leak would be in your brake system and how quickly you can run out if the smallest leak occurs. Again, if your brakes are working properly yet the fluid level is low in the reservoir the main reason for that is because your pads are wearing and filling the brake reservoir up just because it is low isn't always a good thing.

I will explain why in the second part of this article as well as giving some step by step instructions on how to change brake pads and rotors.