Brakes are among the most critical parts of your car. Brake failure can cause you to lose control of your vehicle and get into accidents. It’s, therefore, essential to understand the type of brakes your car runs on for easy troubleshooting and maintenance.
So, are car brakes hydraulic or pneumatic, and what is the difference? Passenger cars run on a hydraulic brake system. Trucks, on the other hand, have pneumatic brakes. The difference between the two is the working element. Hydraulic brakes use brake fluid while pneumatic brakes use compressed air.
Most people understand that trucks and passenger cars run on different types of brakes. However, the majority don’t know how to differentiate between hydraulic and pneumatic brakes or their advantages and disadvantages. In this article, you’ll get a comprehensive comparison of these two types of brakes.
Are Car Brakes Hydraulic or Pneumatic?
A passenger car runs on a hydraulic brake system. To understand how a hydraulic brake system works, you need to know how it differs from its pneumatic counterpart and why one type of brake is preferred for passenger cars over the other.
Before discussing the difference between hydraulic and pneumatic brakes, it’s essential to begin with the similarities that these brakes share.
- Both brakes are used for one purpose – to slow down the vehicle or bring it to a stop.
- All brakes rely on friction.
- Both brake systems feature brake drums, pads, and shoes, connected to the wheel’s axles.
The difference between the brakes is in their main working element:
- Hydraulic brake systems rely on brake fluid to stop the vehicle.
- Pneumatic brakes rely on compressed air.
How Hydraulic Brake Systems Work
Hydraulic brakes are the preferred type of brakes in small vehicles and light trucks. Hydraulic systems use fluids to apply force to objects. For instance, hydraulic systems exert the necessary force required to raise or lower forklift arms.
In a hydraulic brake system, brake fluid is used to provide the force required to stop a vehicle. This fluid is in the engine’s compartment, and it’s drawn into the master cylinder as needed. When you apply pressure on the brake pedal with your foot, the brake fluid is pushed out into the brake lines and into the wheel cylinders in each wheel to stop the car.
In a hydraulic brake system, the wheel cylinders reflect any movement in the master cylinder because fluid is not compressible. 26,000 pounds is generally the weight limit for vehicles that are equipped with hydraulic brakes. But why are these brakes the best for small vehicles?
Hydraulic brakes work well in small passenger cars because they have a light construction and low overall weight. Not to mention, hydraulic brakes require much less storage room compared to pneumatic brakes. Therefore, they’re better suited for smaller vehicles compared to larger vehicles like trucks.
However, according to Godfrey Brake Service, hydraulic brakes are not the best in heavy-duty operation. In such cases, pneumatic brakes are the best.
How Pneumatic Brakes Work
Pneumatic brake systems, also referred to as air brake systems, are mostly found in heavy vehicles such as buses, tractor-trailers, and railroad locomotives. The main reason why pneumatic brakes are used for heavy vehicles is the fact that they provide absolute stopping power. Vehicles that weigh over 33,000 pounds are typically outfitted with pneumatic systems, but you can find air brakes on vehicles as light as 26,000 pounds.
Although hydraulic brake systems have similar braking components at the wheel level as their pneumatic counterparts, the primary difference is how the power is applied to stop the car. To ensure the vehicle has enough stopping power, pneumatic brake systems function on a default status, which means they’re always engaged.
When you step on the brake pedal, strong springs push the brakes into position and hold them in place until enough pressure is available to disengage them. When you let go of the brake pedal, the pressure builds up again and pushes the brake mechanism out of the way once again, thereby enabling the vehicle to move.
However, according to How Stuff Works, there’s more to a truck’s brake system than what meets the eye. There are three different brake systems in a truck, and they are:
- Service brakes: These are used during normal driving. When you step on the brake pedal, you activate the service brakes, which create air movement through the air lines, and the brake linings are forced to make contact with the brake drum.
- Parking brakes: These are activated by pulling one or both of the valves on the dash. The dash releases the spring inside the brake chamber and begins the stopping process.
- Emergency brake: This uses parts of the other two brake systems to bring the car to a stop in the event of brake failure.
Hydraulic Vs. Pneumatic Brakes – Which Is Better?
Pneumatic brakes are more advantageous compared to hydraulic brakes. The primary advantage of pneumatic brakes is their combination of safety and stopping power. As we mentioned, pneumatic brakes are always engaged, and you must take deliberate action to disengage them from their position.
According to the article “Hydraulic Brake vs. Pneumatic Brake,” in the event of a pneumatic conduit brake, the brake will start working and immobilize the vehicle. This isn’t the case with a hydraulic brake system. Because these brakes are not engaged by default, brake fluid leakage or broken brake lines will result in the inability to stop the car.
The other benefit of pneumatic brakes is their stopping power. Although hydraulic brake systems are robust, they lack mechanical backing to provide adequate stopping power. As a result, they are considered secondary to pneumatic brakes.
However, pneumatic brakes have one flaw you won’t experience with hydraulic brakes – brake lag. This is the time it takes for the air to move through the lines and force the linings to contact the drum. When you’re driving a car with pneumatic brakes, you must get used to the fact that the car won’t stop immediately when you step on the pedal. Nonetheless, this isn’t a significant issue because the lag time is only a few seconds.
Other Important Brake Considerations
Apart from understanding the difference between pneumatic and hydraulic brakes, Work Truck recommends familiarizing yourself with the following braking enhancements if you’re a fleet manager:
- Exhaust Brakes: These types of brakes are only available for diesel engines. They close off the exhaust manifold from the engine, thereby creating back pressure in the engine cylinders, slowing down the pistons, and eventually, the entire vehicle. Because exhaust brakes work off the engine and not the wheels, they prolong the life of both pneumatic and hydraulic brakes.
- Anti-Lock Braking Systems (ABS): These are standard for most medium-truck manufacturers for both pneumatic and hydraulic brakes. ABS regulate the amount of pressure to the brakes in the event of severe braking to prevent wheel lock-up and give you control of the vehicle. Most insurance companies will provide you with a discount if you have ABS enabled.
Over to You
As a driver, it’s crucial to understand what type of brakes your car runs on. With this information, you’ll be able to make informed decisions about brake maintenance. Not to mention, it will be easy to know what to expect when driving your car and how to troubleshoot different braking issues. Don’t forget to factor in things like exhaust brakes and anti-lock braking systems if you’re in the market for a truck. These additions not only improve your driving experience but also give you an advantage when you’re seeking insurance.
