Curious about the differences between front and rear brakes?
In the regular car, the front brakes take on most of the braking, while the rear brakes balance that out with added vehicle stability.
But what are the other differences between front and rear brakes?
And how do disc brakes and drum brakes tie into this?
In this article, we’ll answer those questions and cover some brake system FAQs.
This Article Contains
- What Are The Different Kinds Of Brakes?
- Front Brakes vs. Rear Brakes: Why Are They Different?
- How Do Rear Brakes Function?
- How Do Front Brakes Function?
- What’s A Disc Brake?
- What’s A Drum Brake?
- Disc Brakes vs. Drum Brakes
- 4 Brake System FAQs
Let’s get into it.
What Are The Different Kinds Of Brakes?
Automotive brakes are designed to endure incredible forces and temperature changes.
They convert kinetic energy (from your foot) to heat energy (while braking).
However, the braking force isn’t distributed equally across all four wheels. Usually, the front axle takes on far more force than the rear.
With that in mind, you can think of the standard vehicle brake in terms of position and then further divide that into type.
The position defines the amount of work it does:
The type defines how it does the work:
Front Brakes vs. Rear Brakes: Why Are They Different?
Brakes don’t apply force and heat up at the same rate because of the distribution of mass and forces as your car moves.
The overall vehicle design determines the brake bias from front to rear:
- Front brakes handle most of the braking force and build up most of the friction heat.
- Rear brakes take on less braking force but provide stability to prevent spin-outs and rollovers.
Note: Brake bias is the ratio of braking force received by front and rear wheels, usually quoted in percentages.
The type of brakes employed on the front and rear can also be different. Most modern vehicles will have an all-disc brake setup, or have disc brakes on the front axle and drum brakes on the rear (we’ll get into that, next).
How Do Rear Brakes Function?
Rear brakes typically handle less than 40% of the braking force, so they don’t generate as much heat as the front brakes.
The rear brake is designed to provide stability, or else they would lock up every time you hit the brake pedal. If you have bad rear brakes, the rear of your vehicle might jump during hard braking because there’s no stabilizing braking force.
How are rear brakes commonly configured?
1. The master cylinder delivers lower hydraulic pressure to these brakes for less braking power.
2. Rear disc brakes will have physical features that cater to reduced braking force, like:
- Smaller brake calipers and rotors mounted on the rear wheel
- Rear brake pads with a reduced surface area
- Rear pads with less aggressive friction material
- A solid but thinner brake rotor as it doesn’t need to dissipate as much heat
3. A drum brake system is usually used on the rear axle of many economy cars or light trucks. They have less stopping power than disc brakes but are reliable and cheaper to manufacture.
4. The rear brake also incorporates the parking brake (emergency brake).
This configuration is generally accurate for most cars and light trucks.
Larger vehicles may have a different design due to load capacity on the rear.
Now let’s look at the front brakes.
How Do Front Brakes Function?
The front brakes handle up to 75% of a vehicle’s braking load and generate much more heat, which can spike to over 500°F during heavy braking.
Here’s the underlying science behind it all:
When you hit the brakes as the car moves forward:
- The vehicle’s center of gravity shifts forward
- This shift puts more weight and more momentum on the front wheels
- The front wheels gain more traction and can take more braking force to stop the car
How are front brakes typically configured to deal with this?
1. The brake master cylinder delivers higher pressure for a heavy clamping force.
2. Disc brakes are used on the front and usually feature:
- Large, multi-piston brake calipers to deliver strong clamping
- Large brake pad surface areas and more aggressive brake pad friction material for increased friction
- Brake rotors with wider diameters to provide more stopping torque
- A thicker brake rotor to retain shape better at high temperatures
- Ventilated rotors to aid with cooling
Now that we’ve gone over how rear and front brakes differ, let’s take a closer look at the two brake types next.
What’s A Disc Brake?
The disc brake consists of a caliper, brake pads, and a rotor (also known as brake discs).
There are mainly two types of calipers — the floating caliper and the fixed caliper.
The caliper holds the brake pads, is shaped like a C-clamp, and is located over the rotor.
To stop the spinning rotor (which spins with the tire), the caliper clamps down on it with the brake pads.
You’ll find disc brakes mounted on the front axle and sometimes on the rear axle as well. Their superior braking capability over drum brakes makes them perfect for the heavier braking work at the front.
What’s A Drum Brake?
The drum brake is a slightly more complicated design than disc brakes, and the main braking components consist of a wheel cylinder, brake shoes, and a brake drum.
The wheel cylinder has a brake shoe attached to its opposing ends. It pushes each brake shoe against the insides of a spinning brake drum to stop the tires.
The drum brake system is an older brake design but is still very reliable.
However, it doesn’t manage heat dissipation as well as disc brakes, so it’s usually assigned to the rear axle.
Now, how do these two brake types differ?
Disc Brakes vs. Drum Brakes
Here’s a rundown of the differences between disc and drum brakes:
- Braking capability: Disc brakes exert more braking force faster, which translates to shorter stopping distances than drum brakes.
- Heat management: Disc brake components are exposed to air, so they cool off faster. Drum brake components are contained and take longer to dissipate heat.
- Performance in wet conditions: Because of their open design, disc brakes easily sling off water, and your brake discs remain dry relatively easily. Drum brakes take longer to dry up if water gets inside them, exposing the friction material longer to moisture.
- Weight: Disc brakes are generally lighter than drum brakes designed to apply the same amount of braking force. The lighter a vehicle is overall, the easier it is to brake.
- Brake dust accumulation: The drum brake system is closed, so brake dust will accumulate inside and require periodic cleaning. Disc brakes are somewhat “self-cleaning” as the disc brake pads “wipe” the rotor while braking.
Now that you know different brake types, let’s cover some FAQs on brake functionality and maintenance.
4 Brake System FAQs
Here are some answers to questions you may have about the brake system.
1. How Does The Braking System Work?
Ever wondered how the braking system works?
The standard automotive braking system is based on hydraulic pressure.
Braking begins with the mechanical force generated by a foot depressing the brake pedal.
The brake master cylinder then converts that force into hydraulic pressure, which is transmitted through your brake fluid.
The brake fluid is then carried through the brake line to the brake mechanism at the wheel.
The brake mechanism at each wheel converts the hydraulic pressure back to mechanical force, creating friction to slow down the car.
This is done in one of these two ways:
- Drum brake wheel cylinders push brake shoes on to brake drums
- Disc brakes calipers compress rotors with brake pads
2. What’s The Difference Between A Floating And Fixed Brake Caliper?
The floating caliper has one piston, or two mounted on one side.
When the brakes are applied, the floating caliper piston pushes the inner brake pad to contact the rotor. Simultaneously, the caliper body slides closer to the rotor, bringing the outer brake pad into contact as well.
The fixed caliper doesn’t move and is fixed onto the caliper bracket. Unlike the floating caliper, it has a piston array on both sides. When the brakes are applied, only the caliper pistons move, compressing the disc brake pads against the rotor.
Fixed calipers are generally preferred when it comes to performance, but they’re also more expensive.
3. How Does The Parking Brake Work?
The parking brake (or emergency brake) is entirely separate from the hydraulic brake system and is installed onto the rear brake axle.
In rear drum brakes, the parking brake is activated by cables attached to a lever. When the brake lever is engaged, the drum brake shoes push against the brake drum, wedging themselves in place, keeping the rear tire stationary.
Rear disc brakes typically incorporate a parking brake in one of two ways:
- It can contain a corkscrew device that pushes a piston in the rear caliper into the brake pad. This stops the vehicle when the parking brake is applied.
- Alternately, rear disc brakes can also include a separate drum brake system within the rotor hub that acts as the parking brake.
4. When Do My Brakes Need Servicing?
You should get your brakes checked every 15,000 to 20,000 miles.
Be aware of brake noises, especially squealing or grinding (which can come from worn brake pads), and pay attention if the brake warning light turns on. If any of these turn up, get a mechanic to check your brakes as soon as possible.
Final Thoughts
It doesn’t matter if your vehicle uses discs or drums. The most important thing is ensuring that they work. If you notice a drop in braking performance, get hold of a mechanic to give your brake system a lookover.
And if you face any issues, contact AutoNation Mobile Service!
Why AutoNation Mobile Service?
AutoNation Mobile Service’s ASE-certified technicians can perform all kinds of repairs and replacements right in your driveway. All repairs come with a 12 month, 12,000-mile warranty, and you can easily book appointments online.
For an accurate estimate of how much your brake repair will cost, just fill out this online form.