Front Brakes vs. Rear Brakes – What is the Difference?
Is there a difference between front brakes and rear brakes? The front brake is at the front and the rear brake is at the back. That's all you need to know, right? Perhaps, from the most basic point of view, this is "correct", but it is completely misleading. Front brakes vs. rear brakes have to do with friction and heat.
From a physics perspective, car brakes are designed to convert the kinetic energy of a moving vehicle into heat through friction. The result of the energy conversion is stopping your car. Then, vehicle design, including the design of the brakes themselves, helps dissipate heat into the air.
Now, here's the main difference: the heat generated. Looking at the front and rear brakes, specifically the size and weight of the brake discs, brake calipers and brake pad surface area, it's obvious that the front brakes are significantly heavier than the rear brakes, which allows them to take heat.
FRONT BRAKE DESIGN
Let's get back to physics to better understand why front brakes need to handle so much heat. When you drive forward and apply the brakes, the vehicle's center of gravity effectively shifts forward, putting more weight and more momentum on the front tires. As a result, the front tires gain more traction and can withstand greater braking force to stop the car. Because front brakes generate up to 75% of a vehicle's stopping force, they generate more heat, generating over 500°F during hard braking.
This requires developing some common design features:
High hydraulic pressure diverted from the master cylinder provides greater clamping force.
Larger multi-piston brake calipers generate more clamping force.
Larger brake pad surface area increases friction.
More corrosive brake pad materials can also increase friction.
Larger diameter brake discs provide greater braking torque.
Thicker brake discs retain their shape under high temperatures.
Ventilated brake discs dissipate heat faster.
Aerodynamic features of the body and underbody help dissipate heat by driving air through the brakes.
REAR BRAKE DESIGN
The overall vehicle design determines the bias of the front versus rear brakes, but most rear brakes should not provide more than 40% of stopping power at any given time. Therefore, they don't generate nearly as much heat as front brakes. If they weren't designed for this smaller load, the rear brakes would lock up every time the brake pedal was pressed, or at least the anti-lock braking system (ABS) would stay activated.
Providing the right amount of braking power and vehicle stability requires the following conditions:
The hydraulic pressure is low and is diverted from the master cylinder, so the clamping force is small.
Smaller brake calipers also provide less clamping force.
Smaller pad surface and less aggressive pad material reduce friction.
The brake disc diameter is smaller and the braking torque is smaller.
Thinner brake discs are lighter and don't have to withstand as much heat.
Solid brake discs don't have to dissipate as much heat.
Drum brakes on many economy cars offer all of the above benefits.
As you can see, your braking system differs significantly from front to rear. Designed to absorb heat and stop safely, your brakes are designed to get the job done, no matter where they are located.
