Front vs. Rear Brakes: Does it Even Matter?

Even though most modern cars are built with brakes on all four tires, If you have ever needed to replace the brakes on your vehicle, you may have noticed that it is usually the front brake pads that wear out the quickest. While this is a completely normal phenomenon, you might be curious about what the differences between the front and rear brakes actually are, and how they affect the way your car comes to a stop.

Front versus rear brakes: does it matter? While all four brakes play an important role in stopping your car, in most cases, the front brakes take the brunt of the energy that is exerted on the car when it comes to a stop. In fact, the front brakes will often provide anywhere from 60 to 90 percent of the friction required to slow the vehicle. However, more modern cars will split the distribution of energy more evenly to all four tires depending on the brake bias.

While the minutiae of the processes that allow your car to function properly are often completely forgotten about, the truth is, there is a lot of complexity to even the seemingly simple task of bringing a car to a stop. Not every car owner will want to know how this all works, but those who have insight on how their car functions are in a better position when it comes time for maintenance and repairs. So, about those brakes…

Are Car Brakes in The Front or in The Back?

These days, all modern cars are produced with disc brakes on all four wheels. However, the widespread implementation of four-wheel drive braking systems did not become commonplace until the latter half of the twentieth century. But by the 1980s, nearly every car manufactured would include drum or disc brakes, or a mix, on all four wheels.

Although cars with a four-wheel hydraulic braking system had been invented by 1918, the benefits of hydraulics would not be seen for the average consumer until well into the 1940s. This is primarily due to the fact that both the Ford Motor Company and General Motors did not adopt hydraulic four-wheel brakes as a standard until post World War Two.

Practically speaking, however, the front brakes on modern vehicles often do most of the heavy lifting when it comes to bringing the car to a stop, so usually, more attention and care is given to a car’s front brakes.

In other words, the brakes that matter the most are generally going to be the ones at the front of your vehicle, but that is not to say rear brakes are not important, as many newer cars rely more heavily on all four brakes to more evenly distribute energy.

What Is The Difference Between Front and Back Brakes?

By far, the most obvious difference between front and back brakes is their location on a vehicle. The front brakes are in the front and the back brakes are in the back. OK, so it may seem redundant to mention this, but the distinction matters. And they each function a little differently because of their location.

Even though your car may use the exact same type of braking system on both front and back tires, both sets of brakes will handle the transfer of energy differently when coming to a stop.

It is truly more of a question of physics, as the real differences between a car’s front and back emerge when considering how they deal with the friction and heat that is created when the braking system is in use.

Because a car’s front brakes generate so much more heat than the rear, the more noticeable physical differences between the front and rear brakes become more obvious when looking at how they are designed.

Your Car’s Front Brakes

Thanks to Newton’s First law of motion, we know that an object in motion wants to stay in motion. In the context of a car, this means that when you apply the brakes in order to come to a stop, the vehicle’s center of gravity will change and shift forward, applying significantly more downward force onto the front tires and requiring more braking force. So, far more friction is applied to the front brakes, creating excessive heat.

In fact, the front brakes of a car can be subjected to temperatures upwards of 500 degrees Fahrenheit, depending on how fast the car is traveling. Because of this, the most readily noticeable difference between the front and rear brakes is how much thicker and heavier the front brakes have to be in order to dissipate that heat efficiently.

Design Features of Front Brakes:

1. High Hydraulic Pressure: Due to the extra braking force required at the front of the vehicle, the front brakes require a higher amount of hydraulic pressure to be split by the master brake cylinder in order to provide greater clamping force on the tires.
2. Larger, Multi-piston Brake Calipers: Once again, due to the necessity for more braking power, the brake calipers at the front of a car are designed to be larger and include more pistons so that there are fewer points of failure and more surface area for heat absorption.
3. Larger Brake Pads: Front brakes also have larger brake pads. Not only does the extra surface area provide more heat absorption, but the larger brake pads also provide more friction on the rotor.
4. Aggressive Brake Pad Material: It is also very common for a car’s front brakes to use a harsher material on their brake pads. This helps apply more friction to the rotor in order to bring the vehicle to a stop quicker.
5. Larger Brake Rotors: Today, front brake rotors are designed to be larger in diameter than the ones located at the rear of a car. This is done in order to provide more stopping torque when the brakes are applied.
6. Thicker Brake Rotors: Modern front brake rotors are also designed to be much thicker than the rear rotors. The purpose of this is to allow the front brake rotors to maintain their shape when subjected to high temperatures.
7. Ventilated brake rotors: Many cars are produced with ventilated front brake rotors as well, unlike the rotors at the rear. The extra ventilation provides the rotors with another effective way to dissipate the heat caused by hard braking.
8. Aerodynamic Body Features: A majority of modern vehicles also implement aerodynamic features in the chassis of a car which helps direct air through the front brakes to provide extra heat dissipation when the car is at speed.

Your Car’s Rear Brakes

Unlike the brakes at the front of your car, the ones located at the rear are always designed specifically to withstand much lower temperatures and are generally made to be put under less stress when in use. This is also the reason why the braking pads at the front of your car are usually the first to need replacing.

While the brake bias between vehicles can vary quite a bit, the rear brakes of a car will never provide more than 40 percent of the stopping power. This is done to ensure that the rear brakes do not lock up or otherwise cause the Anti-lock Braking System (ABS) to constantly engage. In order to provide sufficient stability to the braking system as a whole, rear brakes include the following design features.

Rear Brake Design Features:

1. Low Hydraulic Pressure: The hydraulic pressure directed to the rear brakes of your car is always split at much lower pressure by the brake master cylinder. This is done because, as previously stated, rear brakes do not require as much braking power.
2. Smaller Calipers: Rear brakes, unlike the ones at the front, use smaller braking calipers. These smaller calipers provide less clamping force on the rotors and thus create less heat and friction.
3. Smaller Brake pads: To go along with the smaller calipers, rear brakes also use smaller brake pads to reduce friction on the rotor. Rear braking pads are usually made from less aggressive material as well.
4. Smaller Brake Rotors: You may notice a trend forming here, as the rear brake rotors on a car are made to be smaller in diameter, unlike their counterparts at the front. These smaller diameter rotors have less stopping torque.
5. Thinner Brake Rotors: Because the rear brakes of a car are subjected to far less heat, rear brake rotors are not only smaller, but thinner as well. There is never a normal situation where the rear brakes are put under enough stress to warrant ventilating the rotors either.
6. Economy Drum Brakes: Despite the age of the technology, many more economically priced cars will use drum brakes for the rear of the vehicle. Because the rear brakes on a car are designed to be produced to a lower spec anyhow, drum brakes make a cheap but effective substitute for more expensive disc brakes while providing all the same benefits.

As you can see, there are many similarities and differences between the front and rear brakes that parallel each other. While both sets of brakes provide the same function, they both accomplish their jobs differently and handle the transfer of energy in their own unique ways to ensure a safe and stable ride for the driver.

Drum Brakes vs. Disc Brakes

While the designs and mechanisms for braking are quite different from each other, perhaps the easiest distinction to be made between disc and drum brakes is the age of the technology.

Even though both drum and disc brakes were invented in the early years of the twentieth century, disc brakes would not become commonplace in consumer vehicles until the well into the 1940s. These days, most cars include superior disc brakes on all four tires.

Of course, the most obvious physical differences between the disc and drum brakes become apparent within moments of looking at them, as they both utilize very different systems in order to provide stopping power to a car’s tires.

Drum Brakes

Drum brake technology first emerged in 1900, used in a car produced by Maybach. These early drum brakes were mechanically operated by a mix of levers, rods, and cables, which would control the “shoes” that are pushed against the interior of the drum.

By 1930 however, the majority of drum brakes would use the oil pressure inside a small wheel cylinder, along with a series of pistons in order to perform braking in within the drum.

Drum Brakes are Constructed of the Following Parts:

1. Backing Plate: Also called the “Torque Plate,” due to the fact that it absorbs the torque created during braking, the backing plate provides a base for all of the other components. Aside from providing the majority of the structural integrity, It also protects the rest of the housing from debris, dust, and other foreign material.
2. Brake Drum: The drum part of a brake drum is usually made out of a special type of cast iron, which is more resistant to heat and wear. The drum rotates along with the wheel and axle of the vehicle. Brake lining is pushed against the interior of the drum to create friction which in turn slows the wheel.
3. Wheel Cylinder: A single wheel cylinder is used inside each wheel drum. Hydraulic pressure coming from the master cylinder forces the pistons outward, pushing against the primary brake shoe and forcing it against the interior of the drum to create the friction required to stop the tires from turning.
4. Brake Shoe: Brake shoes are typically made of two pieces of steel that are welded together to form a crescent-shaped component. Two shoes are used in every drum, a primary shoe, and a secondary shoe, which form a circle inside the drum. Adhesive or rivets are used to apply a high friction brake lining to the exterior of the crescent shoes.

Disc Brakes

While the earliest disc brake designs date back to the late 1890’s England, the first practical disc brake system was developed in 1902 by the Lanchester Motor Company. This early disc brake operated very similarly to modern disc brakes, though the actual discs were much thinner and cable operated.

However, disc brake technology wouldn’t proliferate to consumer vehicles until more than half a century later, during the mid-1960s.

There are Three Major Components of a Disc Brake:

1. The Rotor: The rotor is the “disc” part of a disc brake and is attached at the axle of a car. Jutting out from the outward-facing side of the rotor is the “hub”: a sort of metal mound upon which the tires are bolted to.
2. The Caliper: The calipers on a car’s disc brake function much in the same way as the calipers on a bicycle brake, with a couple of exceptions. When the brakes are activated, a hydraulically operated piston, which is mounted to the calipers, causes the clamp to squeeze against either side of the rotor, much like the calipers on a bike squeeze against its tires.
3. Brake Pads: Much like the brake lining on a drum brake, the pads of a disc brake are made of high friction, heat-resistant material. These pads are attached via adhesive, or by other methods, to each interior side of the brake calipers. When in use, the brake pads are squeezed against the rotor by the calipers, and thus causing the friction required to slow the wheels.

While both disc and drum brakes present their own unique benefits and drawbacks, to some extent, disc brakes are the clear winners when considering longevity and reliability.

Almost all modern vehicles are produced with disc brakes on all four wheels and are not only more resilient but are much easier to maintain and replace if the need arises.

However, there are still plenty of economy vehicles, as well as older cars, which still rely on drum brake technology as a more cost-efficient option. Although the basics of drum brakes have not changed too drastically in over 100 years, thanks to the miracles of modern engineering, brake locking, other shortcomings, have virtually been eliminated as problems in their modern implementation.

Whether your car uses a drum or a disc, it is unlikely we will see any massive innovations which render these systems obsolete, so unless you are experiencing brake trouble, you may as well not concern yourself with the details.

More Brakes!

Though you may not have known it, the world of brakes is a vast and complicated place with far more nuance than even your average motorhead may realize. While this article certainly does not cover all that there is to know about vehicle braking systems, we hope this at least clears up a few of the bigger concepts in braking.

If for some reason, you are still not satisfied and would like to find out more about the history of car brake development, or if you simply want to know more about how the brakes in your particular car work, we suggest trolling the various car forums around the internet or asking your local mechanic.