It turns out an expert truck driver rarely touches the brakes. A quick back of the envelope of what it takes to stop an 80,000 pound truck going 60 mph quickly convinces you that the life expectancy for normal disk or drum brakes would be very short.
The trick is to use an engine braking system. Jake Brakes are the most common. I didn't realize the idea came from the same Cummins who founded the engine company of the same name, but it makes sense.
You can get a braking effect in by downshifting – without adding fuel to the engine. As the engine goes through the compression stroke some of the energy of your motion is used to compress the air. A Jake Brake modifies the timing on the exhaust valves so that when you want to brake, the valves open as the piston reaches the top of the compression stroke (without this trick some of the energy in the compressed air would drive the piston down – getting the energy out of the engine dramatically increases the braking efficiency).
Setting up a Jake Brake is something of an art and some truckers take pride in coast to coast trips without touching the normal brakes.
5:57:09 AM
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