Front Brakes vs. Rear Brakes : What's the Differences

What Are the Different Types of Brakes?

Automotive braking systems are engineered to withstand immense forces and fluctuations in temperature. Their primary function is to convert kinetic energy, generated by pressing your foot on the brake pedal, into heat energy during the braking process.

However, the distribution of braking force is not uniform across all four wheels. Typically, the front axle bears a significantly greater portion of the force compared to the rear.

Considering this, one can categorize standard vehicle brakes based on their position, further dividing them by type.

Position determines the workload:

- Rear brakes

- Front brakes

Type determines the method of operation:

- Disc brakes

- Drum brakes

Front Brakes vs. Rear Brakes: Understanding the Variance

The dissimilarity in force application and heat generation between brakes stems from the distribution of mass and forces as a vehicle moves.

The overall vehicle design dictates the brake bias, dictating the distribution of braking force from front to rear:

Front brakes bear the brunt of braking force and accumulate the majority of friction heat.

Rear brakes handle less braking force but play a crucial role in ensuring stability, preventing spin-outs, and averting rollovers.

Note: Brake bias refers to the proportion of braking force allocated to the front and rear wheels, often expressed in percentages.

Additionally, the type of brakes utilized at the front and rear can differ. Many modern vehicles feature either a complete disc brake system or employ disc brakes on the front axle and drum brakes on the rear (details on this follow in the next section).

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 Do Rear Brakes Function?

Rear brakes, typically handling less than 40% of the braking force, consequently generate less heat compared to 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.

Common configurations of rear brakes include:

1. The master cylinder provides reduced hydraulic pressure to these brakes, resulting in lower braking power.

2. Rear disc brakes are tailored for decreased braking force, often featuring:

   - Smaller brake calipers and rotors affixed to the rear wheels.

   - Rear brake pads with reduced surface area.

   - Pads designed with less aggressive friction material.

   - Thinner, solid brake rotors as they require less heat dissipation.

3. Drum brake systems are prevalent on the rear axle of many economy cars or light trucks. While they offer less stopping power than disc brakes, they are dependable and cost-effective to manufacture.

4. The rear brake system incorporates the parking brake (also known as the emergency brake).

This configuration generally applies to most cars and light trucks. However, larger vehicles may feature distinct designs due to rear load capacity considerations.

Next, let's delve into the functionality of the front brakes.

How Do Front Brakes Function?

Front brakes handle a substantial portion, up to 75%, of a vehicle’s braking load and consequently generate considerably more heat, sometimes exceeding 500°F during intense braking.

The fundamental science governing this phenomenon involves:

When brakes are applied while the vehicle moves forward:

- The vehicle's center of gravity shifts forward, placing increased weight and momentum on the front wheels.

- Front wheels, thus, gain more traction and capacity to handle greater braking force for stopping the car.

How are front brakes typically configured to manage this situation?

1. The brake master cylinder exerts higher pressure, enabling a robust clamping force.

2. Front disc brakes are commonly employed, often featuring:

- Large, multi-piston brake calipers to deliver substantial clamping force.

- Expanded brake pad surface areas and more aggressive friction materials for heightened friction.

- Brake rotors with wider diameters to provide enhanced stopping torque.

- Thicker brake rotors to maintain shape integrity under high temperatures.

- Ventilated rotors to facilitate cooling.

Having discussed the distinctions between rear and front brakes, let's delve deeper into the specifics of these two brake types next.

What is a Disc Brake?

A disc brake comprises a caliper, brake pads, and a rotor, also known as brake discs.

Calipers generally exist in two forms: the floating caliper and the fixed caliper.

The caliper, resembling a C-clamp, houses the brake pads and is positioned above the rotor. Its function involves gripping the spinning rotor (which rotates with the tire) using the brake pads to initiate braking.

Disc brakes are typically installed on the front axle and sometimes on the rear axle. Their superior braking capability, compared to drum brakes, renders them ideal for handling the more substantial braking demands at the front of the vehicle.

What is a Drum Brake?

The drum brake represents a slightly more intricate design compared to disc brakes. Its primary components include a wheel cylinder, brake shoes, and a brake drum.

The wheel cylinder attaches a brake shoe to each of its opposing ends. This arrangement allows the wheel cylinder to push each brake shoe against the interior surface of a rotating brake drum, facilitating tire cessation.

Although the drum brake system is an older design, it remains highly dependable. However, it doesn't disperse heat as effectively as disc brakes, typically relegating it to the rear axle.

Now, in what ways do these two brake types differ?

Differences Between Disc Brakes and Drum Brakes

Let's explore the distinctions between disc and drum brakes:

Braking Capability: Disc brakes can exert greater braking force more rapidly, resulting in shorter stopping distances compared to drum brakes.

Heat Management: Disc brake components are exposed to air, allowing for faster cooling. In contrast, drum brake components are enclosed, taking longer to dissipate heat.

Performance in Wet Conditions: Disc brakes, due to their open design, are more adept at shedding water, keeping brake discs relatively dry. Conversely, drum brakes, if exposed to water, take longer to dry, leaving the friction material exposed to moisture for an extended period.

Weight: Generally, disc brakes tend to be lighter than drum brakes designed to deliver similar braking force. A lighter vehicle overall makes braking easier.

Brake Dust Accumulation: Drum brake systems, being enclosed, accumulate brake dust inside, necessitating periodic cleaning. Disc brakes have a somewhat "self-cleaning" mechanism, with the brake pads essentially wiping the rotor during braking, reducing the buildup of brake dust.