Normal Braking Operation and Controls
How a good stop feels
Apply the treadle progressively and squeeze rather than stab. Air brakes have lag: pressure takes time to travel to the chambers and to exhaust afterwards, so plan stops early and brake earlier than you would in a car. Total stopping distance grows quickly with weight and speed because kinetic energy rises with the square of speed. Use the transmission and any retarder or engine brake to control speed, and use the service brakes for the final controlled stop.
On a downgrade
Select a low enough gear before you start down, then use snub braking: apply firmly to bring the speed roughly 10 to 15 km/h below your safe descent speed, release fully and let the speed build back, then repeat. This gives the drums time to cool. Holding a light, continuous application overheats the brakes, causes fade and glazing, and can leave you with nothing when you need it.
Controls and traps
Know the yellow diamond push-pull parking control and the red trailer supply valve, and remember the trailer hand valve is for testing trailer brakes only - never for stopping or parking. After parking, do a tug test to confirm the brakes hold. Frequent traps: pumping the brakes during a normal stop (wastes air), using the hand valve to slow down, riding the pedal down a hill, and believing a retarder makes you safe on ice - an engine brake on a slippery surface can cause a drive-axle skid or jackknife.
Rule of thumb
Brake to a speed, release, repeat. If you cannot hold your descent speed without continuous braking, you were in too high a gear and should stop and change down before continuing.