Hauling in mountainous terrain one can enjoy scenic vistas all around. The view is often spectacular. But it can and will be dangerous if you don’t manage your speed to match the load. One veteran driver we spoke with related his first experience with downhill peril.
“I learned how to drive in the days before engine brakes and retarders. It was my very first trip and with a 40,000 pound load in the reefer on my way east through North Carolina. Things were going fine while climbing uphill grades. But when I crested Black Mountain I had a full head of steam.
“There were no CDL schools in those days and I quickly found myself and the load speeding down the mountain. I had been advised by the truck’s owner to ride the brakes continuously on steep downgrades to keep the speed down. It worked for a while to rein in the truck but required more brake pressure than originally thought sufficient.
“As I neared the bottom of the grade I was using a heavy brake application but wasn’t slowing. When the highway flattened out I was able to safely slow and stop. I climbed out and looked at the brake drums between the wheel spokes. I felt a sudden chill as the drums glowed cherry red.”
Engine Brakes and Retarders
Nowadays we have engine brakes and retarders to help us control our speed on downgrades. Truck brakes are for stopping a truck and are not meant for controlling speed downhill. Know the geography of areas you will be traversing.
When you approach a steep decline, slow and downshift to a gear that will be slow enough to get you safely down the grade. Patience is still a virtue and can save lives, including yours. You will still need to use brakes but with much less pressure and less heat buildup that can cause brake fade which can lead to brake failure.
An engine brake (also called the Jake Brake) changes the function of exhaust valves to turn the engine into a compression air pump to slow the tractor’s drive wheels, thereby slowing the truck. It is an effective way of conserving truck braking and reducing heat buildup of the brake drums on steep down grades.
Jake Brakes also result in more efficient truck operation by saving fuel and leading to shorter trip times.
An exhaust brake creates a situation similar to the Jake Brake. Exhaust flow is restricted which increases exhaust backpressure causing the engine to need to work harder to get rid of exhaust gases. The result is effective engine braking which saves service brakes on down grades.
Snub and Roll
Snub and roll braking is another way of effectively managing loaded truck speed on downhill grades. It consists of heavier brake applications than riding brakes. Use snub braking to slow the truck by 5 miles per hour then release the brakes and roll brake free until the speed creeps up.
Cycle between snub braking and rolling to maintain safe speed on long steep downhill grades. The rolling or coasting time between brake applications allows time for brakes to cool and manage speed without excess heat buildup. Snub and roll braking serves to avoid brake fade from heat.
Snub and roll braking is what you need to practice in the event of engine brakes or exhaust brakes failing to operate. This is your safest backup option until repairs of the failed engine or exhaust brakes can be completed.
Of course, all brake systems require regular maintenance to remain in top operating condition. And we cannot stress enough the importance of pre-trip inspections that must be performed with serious intent to uncover any fault. Diligent inspections are key to saving lives, even yours.
And putting off maintenance in favor of hauling another load will almost always come back to bite you, either in the wallet, in the hospital or worse. Don’t put it off; lives could be at risk. Get a fleet repair shop management system to help with scheduling PMs and performing them on time.