A spring parking brake can exert a force of up to 2,000 pounds. A brake chamber with a spring brake has two diaphragms: a service brake diaphragm and a spring brake diaphragm. A common type of brake chamber for drive axles is the Type 30/30, which has a 30-square-inch service brake diaphragm and a 30-square-inch spring brake diaphragm. For 80 psi of pressure, 80 × 30 = 2,400 pounds of force, which will be enough to counteract the force exerted by the spring parking brake.