Just about every component that's part of the car's brake system is vital to the safety and performance of your vehicle. Along with making sure your brake rotors are properly wearing, your brake pads have enough pad life left, your brake fluid is not contaminated, now you also have to deal with ensuring that your brake lines are operating as they were designed to.
Not to worry, as we want to make sure you understand how your brake system works without having to be a professional automotive technician! In order to understand the role of the brake lines, let's quickly go over the overall layout and function of the brakes. This quick and dirty visualization leaves out a lot of detail for the purpose of understanding the place for brake lines.
When you press down on your brake pedal in your car, hydraulic fluid is being forced from that single pedal, to the master cylinder, and then to all four of your brakes. The master cylinder essentially takes the pressure of your foot on the pedal, and converts it into useable hydraulic pressure. This pressurized hydraulic fluid then travels down through brake lines to each of your four brake calipers. This same pressurized brake fluid then compresses the pistons inside your brake calipers, forcing your brake pads to squeeze together essentially slowing down your brake rotors.
So why is it essential to replace old brake lines? First, almost all of the factory brake lines are normally made out of rubber hoses. As we know, rubber becomes brittle and loses its inherent characteristics as it gets exposed to weather and age. Instead of pressurizing the piston inside the caliper, the brake lines will expand or crack. What does this mean? It means that all the energy your foot is exerting is not going into slowing the car down, but just expending the brake lines (think of a garden hose with the end capped off and the hose expending).
Essentially, you are at risk of losing braking power or complete control of your brakes should any of the brake lines burst. It's important to inspect your brake lines during your routine inspections and every time you change your brake rotors or brake pads.
Lastly, there are also stainless steel braided brake lines, which offer a more consistent brake feel and much better longevity against bursting and cracking.