On a disc/drum system, the rear drum brakes lock up when the brake pedal is pressed hard. Technician A says the proportioning valve may not be functioning. Technician B says the axle height valve may be out of adjustment. Who is correct?
A)A only
B)B only
C)both A and B
D)neither A nor B

Question

Quizplus · Accepted Answer

Both Technician A and Technician B are correct. The proportioning valve, which limits the pressure to the rear brakes to prevent lockup, may not be functioning properly. The axle height valve, which adjusts brake pressure based on the load and height of the vehicle, could also be out of adjustment, affecting brake performance.

On a Disc/drum System, the Rear Drum Brakes Lock Up