Ch – 31 Air Brake Servicing

A 161/2 inch brake drum specified to have a machine limit of 0.090 inch over and a maximum dimension of 0.120 inch over is measured at 0.098 inch over at a brake overhaul. Technician A says that the drum can be turned on a drum lathe, providing that the maximum dimension of 0.120 inch is observed. Technician B says that the drum can be legally returned to service without being turned. Who is correct?
A tandem axle trailer equipped with S-cam brakes has all four slack adjusters originally set with a 6-inch dimension from the clevis pin to the camshaft. One slack adjuster is replaced, and because of a different hole arrangement in the new slack adjuster, it is set at 61/2 inches. Which of the following is more likely to result?
When adjusting a manual slack adjuster on an S-cam foundation brake, Technician A says that the lock collar should be retracted and the adjusting nut always rotated clockwise to decrease free travel. Technician B says that free travel can be reduced only when the adjusting nut is rotated counterclockwise. Who is correct?
A set of brake linings has become glazed because of oil saturation by a failed wheel seal. Technician A says that pressure washing the foundation brake components should be sufficient to remove the effects of the oil saturation. Technician B says that the best practice is to replace the brake linings on both wheels on the affected axle. Who is correct?
An original equipment 45-degree elbow on a line exiting a relay valve supplying a service chamber is replaced by a 90-degree elbow. Technician A says that this should have no effect on brake performance because it is the service application pressure that determines braking force. Technician B says that the use of the 90-degree elbow increases flow restriction and can affect pneumatic timing. Who is correct?
Technician A says that the service diaphragm in a spring brake can be safely changed, providing that the spring brake is properly caged with a cage bolt before removing it. Technician B says that it is no longer possible to change the hold-off diaphragms in most spring brake assemblies because the band clamp cannot be unbolted. Who is correct?
A tri-axle trailer is equipped with five S-cam slack adjusters correctly set at an effective length of 6 inches and one incorrectly installed at 51/2 inches. How much less brake torque will be applied at the brake with the incorrectly set slack adjuster when the service application pressure is 100 psi on a 30-square-inch chamber?
A leaking axle seal has saturated the brake shoe linings and caused them to glaze. Technician A says that the shoes should be immersed in solvent before being returned to service. Technician B says that if the brake shoes on both sides of the axle are not replaced, brake torque balance could be affected. Who is correct?
Technician A says that it is good practice to machine a new drum before putting it into service because it trues the drum to the wheel. Technician B says that most heat discoloration and checking is easy to remove on used drums when brakes are serviced by skimming the drum on a lathe. Who is correct?