Understanding the need for automotive brakes is not a difficult concept and I'm sure we can all conjure up a gruesome, horrifying picture of what could happen if our car did not have brakes, or worse, if those brakes failed when we least expected it.
Most of us, however, have a limited understanding of is happening when we step on the brake pedal, and therefore, we are even more clueless as to what our mechanic is saying when he's telling us that our rotors need turning - or worse, that they need to be replaced.
In this article, we will take a simplified look at the parts of your car's braking system and how it all works.
First, we'll look at the brake pedal.
This is the mechanical part of the system.
Alone, obviously, such a small apparatus of metal and rubber could not stop a speeding car by being pushed just a few inches.
That pedal, however is just a small part of larger picture.
Underneath your car, the brake pedal attaches to a hydraulic system that has much more power and responsiveness than a mechanical system can supply.
Hydraulic systems rely on an incompressible fluid, typically an oil of some sort.
In this case, that oil is known as brake fluid.
So, now, we can begin to imagine what is happening - you step on the brake pedal, which moves a lever that connects to an oversized "plunger" (a.
k.
a.
a piston in mechanic language) that begins pushing on the brake fluid.
This happens in a place called the master cylinder.
Obviously since the pressure of the plunger cannot squish or flatten the brake fluid, it has to go somewhere.
That somewhere is through brake lines that travel underneath your car towards your four wheels.
Before we go any further, let's talk about the kinds of brakes that exist in modern cars.
Your car may have disk brakes, drum brakes, or a combination of the two.
Most cars have disk brakes in front and either disks or drums in the rear.
To determine what type of brakes your car has, simply look between the spokes of your wheels.
If you can see a smooth, flat surface that is somewhat shiny, you have disk brakes.
Disk brakes are a flat plate that spins with your wheel.
When you brake, a "hand" (a.
k.
a.
the caliper and brake pad) squeezes one section of the spinning disk (rotor), causing it to slow down or stop spinning.
You can imagine this sort of like a Frisbee flying through the air and your hand reaching out and grabbing it.
Drum brakes have a different make up.
The drum is shaped like a bowl that spins with your wheel.
Nesting inside that bowl, but not touching it, are brake shoes.
When you step on the brake pedal, the brake shoes respond by pressing outward, coming in contact with the sides of the bowl, or drum.
The friction resulting from these shoes pressing against the spinning drum cause the drum and wheel to stop spinning, and therefore, the car to stop.
So now, we've stepped on the brake pedal, the plunger in the master cylinder has pushed brake fluid through tubes to the four corners of your vehicle.
If you have disk brakes, that brake fluid that was forced out of the master cylinder still has to go somewhere, so it pushes against two pistons in the brake caliper, causing the brake pads to be squeezed against the rotor - remember the hand grasping the Frisbee concept.
The process is quite similar with drum brakes.
The brake fluid that traveled to those brake units enters the wheel cylinder, forcing the shoes to be pushed out against the drum.
The friction again stops the drum, and the wheel, to stop spinning.
Once the brake pedal is released, the brake fluid is no longer being pushed out of the master cylinder, down the brake lines, and against the pads or shoes, which allows the friction to stop and the wheel to turn again.
As you can see, this is a complex system with many parts that can suffer damage and wear.
Now that you have the basic terminology and working knowledge, we can begin to discuss the maintenance and repairs that need to happen to keep your car safe and functional.
Take a look at the next article in my series, titled "Brakes - When Things Go Wrong or Wear Out.
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