Automotive engineering fundamentals: The advantages of hydraulic brake systems

13 / 07 / 2021


Hydraulic brakes are the standard for the new line of sophisticated and futuristic vehicles we’re seeing on the market today. From an automotive engineering standpoint, they are more efficient and last much longer—and that’s why understanding how these systems work is the bread and butter for automotive technicians today, or even for enthusiasts and students learning the ropes.

Using fluid to slow the motion of a vehicle down, these systems leverage a piston rod that connects the brake pedal to the master cylinder (which contains brake fluid); when drivers apply pressure to the brake pedal, it is converted into hydraulic pressure.

The pressure that is generated is then spread throughout the system via hydraulic lines. It forces the wheel cylinder outwards, pushing the brake shoes against the brake drums and stopping the vehicle.

Beyond just understanding how a hydraulic brake system works, however, let’s take a look at how it enhances the performance and durability of a vehicle.

The performance advantages of hydraulic brakes

According to Pascal’s Law, when pressure is directed through a fluid, the pressure is applied equally in all directions. Hydrostatic pressure is equal in all directions and hydraulic brakes are based on this principle.

This means that the pressure applied on the brake pedal is transmitted uniformly through the brake fluid, which guarantees that equal force is applied to each wheel and that vehicles in motion stop quickly and safely.

Hydraulic leverage is another principle of fluid mechanics that can help us understand the advantages of hydraulic brakes.

By transmitting pressure through a fluid, we can multiply the pressure that is applied on the brake pedal before it reaches the wheels. This means hydraulic brakes are great at stopping large vehicles, like trucks, and vehicles moving at fast speeds.

The structural advantages (and why they’re long-lasting)

Brake fluid acts as a lubricant; a fact that helps reduce frictional loss when vehicles are braking at high speeds. It also increases the resistance of vehicular components against wear and tear.

This system of brakes has no joints either. With virtually no vulnerable components, they rarely require part replacements. Forming a simpler build and one that’s much lighter in weight, they produce less thermal stress compared to mechanical brakes, which, in the long run, helps them stay functional and efficient for much longer.

Hydraulic disk brakes also provide more braking power because they have a greater contact area, which supports heat dissipation. They also rarely fail, making them reliable at high speeds and work better compared to mechanical brakes in wet and muddy conditions.

Hydraulic brake vs mechanical brakes vs pneumatic brakes

Mechanical brakes are much cheaper compared to hydraulic or pneumatic brakes but not as efficient, and are mostly used for motorcycles nowadays. Hydraulic brakes have replaced them in household vehicles while pneumatic brakes have replaced them in heavy vehicles designed for commercial use.

Hydraulic systems also boast better braking efficiency and anti-fade characteristics. Unlike mechanical systems, they are self-compensating and self-lubricating, making them doubly advantageous. 

One disadvantage of hydraulic brakes, however, is that they can pose the threat of leaks. On the whole, they are more flexible, feature a simpler construction and offer a better mechanical advantage.

Pneumatic brake systems use compressed air as a working medium instead of brake fluid, take up more space and are complicated and expensive to build and maintain.

Because they are more powerful than hydraulic brakes, however, they are better suited for buses, trucks and freighters. That said, when considered from an overall automotive engineering perspective, hydraulic systems are more efficient, flexible and cost-effective than either mechanical or pneumatic brake systems.

Today, most automobiles including jeeps and vans, family vehicles and even sports cars use hydraulic brakes exclusively. Compared to the other technology available, they offer exceptional value for money and ease of use that’s unparalleled.

Electric brakes that use powerful electromagnets are an emerging technology that might one day replace hydraulics. But widespread use seems at least a decade away—till then, as an automotive engineer, you may find yourself working on plenty of hydraulic brake systems.



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