The Physics Behind Braking

Like so many systems we use on a daily basis, we trust our brakes to work without thinking about why they do. However, the physics of braking a vehicle tells us something very important about what kinds of brakes we need and why. We’ve mentioned you need to ditch the drum brakes with one of Pirate Jack’s disc brake conversion kits, but we hope that after we explain the physics of the brake, you’ll understand why an efficient braking system is vital to the safety of your restoration.

Conservation of Energy

You probably learned it in physics class as a high schooler, but the Law of Conservation of Energy simply states that energy is always conserved. In other words, energy cannot be created nor destroyed, it can only transform into a different kind of energy. This is seen everywhere:

• Energy is released when your body breaks down food, and this energy transforms into motion (walking, talking, etc.), as well as fuel for your body’s natural processes.
• The heat produced by combustion in your car’s engine transforms into kinetic energy, which allows your car to move forward.
• The kinetic energy of your car in motion is transformed (by friction) into heat energy when you stop.

Kinetic Energy

Kinetic energy, or the energy of motion, is determined by two factors: the mass of an object and the speed at which it is traveling. This means an object that is not moving (i.e. it’s speed is zero), has no kinetic energy. Similarly, a massive object in motion, such as a 16-wheeler on the highway, has an enormous amount of kinetic energy.

Kinetic Energy to Heat

When you stop a moving car, it goes from having kinetic energy to having none at all. However, we know by the Law of Conservation of Energy that all of the energy used to move the vehicle has to go somewhere; in particular, kinetic energy is transformed into heat energy.

Because energy is always conserved, the amount of heat produced when you stop a moving object is directly proportional to its kinetic energy. Because kinetic energy is reliant on mass and speed, this means the heat produced by stopping a vehicle will also be proportional to the vehicle’s mass and speed. This is why a 16-wheeler moving at 50 miles per hour is going to produce more heat (and wear through brakes faster) than a compact car going 60 miles per hour.

Braking Systems and Heat Saturation

One of the major problems facing brake manufacturers is heat saturation, which is what happens if the brakes are too hot and can no longer absorb heat. If your brakes can’t absorb heat, kinetic energy can no longer be transformed, which means you won’t be able to slow down or stop. In the world of cars, this is most often referred to as your brakes “overheating.”

Now that we understand that the production of heat and keeping brakes cool are essential elements to stopping properly, it is important to find a car braking system that will remove the heat from the system as soon as it is produced. Unfortunately, drum brakes are not made to cool down as quickly as disc brakes, which are specifically designed to increase airflow, increase surface area, and thus decrease heat saturation.

If you are looking for better performance, better stopping power, and better aesthetics, it’s time to consider buying a disc brake conversion kit. The science doesn’t lie.