For heavy commercial vehicles, air brakes offer significant advantages as compared with hydraulic brakes. Air brakes can apply a much greater force (up to 3,000 pounds) to each foundation brake than hydraulic braking systems can. Air brakes are also more tolerant of slow leaks. If enough hydraulic fluid leaks, you must replenish it before the brakes fail. If compressed air starts to leak, the air compressor can just generate more compressed air. On the other hand, air is much more compressible than hydraulic fluid, which can result in an air brake lag time of up to 0.4 seconds between the time you press the brake pedal and the time that the brakes are fully applied.