Is there a difference between front brakes vs rear brakes? The front brakes are in the front, and the rear brakes are in the rear. That’s all you need to know, right? Perhaps, on the most basic level, that would be “correct,” but entirely misleading. The front brakes vs rear brakes comparison has everything to do with friction and heat.
From a physics standpoint, the brakes on your car are designed to convert the kinetic energy of your moving vehicle into heat energy, via friction. The result of that energy conversion is what brings your car to a stop. Then, vehicle design, including that of the brakes themselves, helps to dissipate that heat to the air.
Now, here’s where the major difference arrives: the amount of heat generated. Taking a look at the front brakes and rear brakes, especially the size and weight of the brake rotors, brake calipers and surface area of the brake pads, it’s obvious that the front brakes are a lot heavier than the rear brakes, enabling them to take the heat.
Front Brake Design — Hot Stuff
Back to physics for a moment, to further understand why the front brakes need to handle so much more heat. When you’re moving forward and you hit the brakes, the center of gravity of the vehicle effectively shifts forward, putting more weight and more momentum on the front tires. The front tires therefore gain more traction, and they can take more braking force to stop the car. Because the front brakes generate up to 75 percent of the vehicle’s stopping force, they generate much more heat, over 500°F in heavy braking.
This has necessitated the development of a few common design features:
- High hydraulic pressure, split by the master cylinder, delivers more clamping force.
- Larger and multi-piston brake calipers develop more clamping force.
- Larger brake pad surface area increases friction.
- More aggressive brake pad material also enhances friction.
- Larger diameter brake rotors for more stopping torque.
- Thicker brake rotors maintain their shape at high temperatures.
- Ventilated brake rotors dissipate heat faster.
- Aerodynamic features in the body and under the car drive air through the brakes, aiding in heat dissipation.
Rear Brake Design — Stability
Overall vehicle design determines front brakes vs rear brakes bias, but most rear brakes should never provide more than 40 percent of the stopping power at any given time. As such, they don’t develop nearly as much heat as the front brakes. If they weren’t designed for this lesser load, the rear brakes would lock up every time you stepped on the brake pedal, or at least the anti-lock braking system (ABS) would be activating all the time.
Providing just the right amount of braking power and vehicle stability requires the following:
- Low hydraulic pressure, split by the master cylinder, has less clamping force.
- Smaller brake calipers also give less clamping force.
- Smaller brake pad surface and less aggressive brake pad material for decreased friction.
- Smaller diameter brake rotors for less stopping torque.
- Thinner brake rotors are lighter and don’t have to endure that much heat.
- Solid brake rotors don’t have to dissipate that much heat.
- Drum brakes, on many economy cars, with all the above benefits.
As you can see, there’s quite a difference in your braking system, from front to rear. Built to take the heat and stop your car safely, no matter where they are located your brakes are designed to get the job done.
Check out all the brake system parts available on NAPA Online or trust one of our 17,000 NAPA AutoCare locations for routine maintenance and repairs. For more information on your brakes, chat with a knowledgeable expert at your local NAPA AUTO PARTS store.
Photo courtesy of Wikimedia Commons