Downhill Grade With a Loaded Tanker After a Brake Fade Warning
You are driving a three-axle tanker with a smooth-bore barrel loaded to 80 percent capacity with a liquid cargo that has no baffles. Gross weight is 78,000 lb. You are descending a 6 percent grade posted with a 35 mph advisory speed and a sign reading "Trucks Use Lower Gear." You are in 6th of 10 gears at 40 mph and the engine retarder is on high. After one minute, your service brakes are needed more often to hold speed, and the pedal feels softer with a longer stroke. The grade continues for another mile with a gentle curve at the bottom. Traffic behind you is light, and the shoulder is narrow with a drop-off.
1. What do the softer pedal and longer stroke most likely indicate, and what should you do right now?
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A soft, long-travel pedal after repeated use on a grade points to brake fade from heat, often combined with overheated brake fluid or linings that have lost friction. This is a warning, not a normal condition. Do not pump the brakes or continue riding them. Shift to a lower gear immediately to increase engine braking, let the retarder do more of the work, and reduce speed before the curve. If the pedal continues to fade or you cannot hold speed, use an escape ramp if one appears, or bring the vehicle to a controlled stop on the shoulder using the least brake necessary. After stopping, let the brakes cool and check for drag, smoke, or fluid leaks before continuing. Never continue down the grade hoping the brakes recover on their own.
2. How does the unbaffled, partly filled tank affect your stopping and steering on this grade, and how should you adjust?
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A partly filled tank with no baffles lets the liquid surge forward when you brake and side to side in the curve. Forward surge adds load to the steering axle and can push the vehicle, and side surge can cause a rollover or loss of control at the bottom curve. The surge also makes the brake pedal feel uneven. Adjust by slowing well before the curve, using smooth, progressive braking rather than hard stabs, keeping both hands on the wheel, and avoiding abrupt steering. Because the load is shifting, increase your following distance and leave room to stop. On a grade, the safest plan is to be in the correct low gear before the descent and to keep speed low enough that the liquid stays settled rather than sloshing.