What is the difference between air brakes and hydraulic brakes?
2 Answers
The differences between air brakes and hydraulic brakes are as follows: 1. Hydraulic brakes have a simpler structure and require less installation space. They only need a master cylinder, wheel cylinders, a fluid reservoir, and connecting pipelines, without requiring additional auxiliary equipment. Air brakes are more complex than hydraulic brakes. In addition to the master cylinder, wheel cylinders, and brake pipelines, they also include components such as an air compressor, air reservoir, high-pressure controller, and relay valve. They require more installation space, and to ensure safety, the rear wheel cylinders now use air-cut brakes. 2. Hydraulic brakes have a slightly slower response time, provide smoother braking, and exert less force. Air brakes respond quickly, deliver more aggressive braking, and exert greater force. Therefore, hydraulic brakes are generally used in small and medium-sized vehicles, which are compact, have a simple structure, and are lightweight, thus not requiring excessive braking force. In recent years, there has been a trend toward using hydraulic brakes in medium-sized vehicles (with a load capacity below 10 tons, such as some medium-sized buses with fewer than 19 seats). Air brakes are mostly used in large trucks and buses, which have ample space, require greater braking force, operate over long distances, and need fast response times. The additional cost is relatively insignificant compared to the overall vehicle cost.
I drove heavy trucks with air brakes for over a decade, and now switching to hydraulic brakes in passenger cars gives me deep reflections. Air brakes rely on compressed air to push brake pads, featuring air tanks, pipelines, and valves in the system. They provide strong braking power under heavy loads, especially resisting overheating during long hauls or towing, but require periodic drainage maintenance due to moisture in the air—otherwise, winter freezing becomes problematic. Hydraulic brakes, common in cars and light vehicles, use brake fluid to transmit pressure, offering instant pedal response and refined control ideal for urban driving. However, fluid leakage leads to complete failure requiring repair. Cost-wise, air brakes are pricier with complex installations while hydraulic systems are more maintenance-friendly. I recall a mountain drive where failed hydraulics forced me to coast to safety using the handbrake, whereas air brake issues still allow marginal stopping distance—each has distinct safety trade-offs.
