Caprock Grades and Brake Fade: What Happens on the US-84 Descent

The climb and descent between Post and Lubbock is what finds brakes that were fine on flat driving. How fade actually happens and how to avoid it.

Most driving on the South Plains is flat, and flat driving is easy on brakes. You slow from speed occasionally, the pads have time to cool between stops, and a set that is well past its best can feel perfectly adequate for months.

Then somebody takes a loaded truck down the Caprock on US-84 toward Post, or comes off the escarpment on 82 east of Crosbyton, and finds out where those brakes really were.

What brake fade actually is

Brakes work by turning motion into heat. On a normal stop that heat goes into the rotor and dissipates into the air before the next one. On a sustained descent you are braking more or less continuously, and the heat has nowhere to go.

Two things then happen, and they are different failures:

• Pad fade. The friction material gets hot enough that its coefficient of friction drops. The pedal still feels firm — you push it and very little happens. This is the frightening one because the pedal gives you no warning.
• Fluid fade. Brake fluid absorbs water over time, and water boils far below the temperature the fluid is rated for. Boiling produces vapour in the lines, vapour compresses, and the pedal goes soft and travels to the floor.

How to descend a grade properly

1. 1Get your speed down before the descent, not during it. Braking to control an already-excessive speed is what overheats brakes.
2. 2Select a lower gear and let engine braking do the work. This applies to automatics too — most will hold a lower gear manually.
3. 3Use firm, brief applications with gaps between rather than continuous light pressure. Riding the brake is the single fastest way to overheat it.
4. 4If the pedal starts going soft or long, pull off and let everything cool before continuing. There is no technique that recovers boiled fluid at speed.
5. 5Trailer brakes matter. If you are towing, the trailer should be doing its share.

Measured, not estimated

The only honest way to know where a set of pads is sitting is to measure the friction material and the rotor thickness. Looking through a wheel tells you very little, and a mileage estimate is worthless on a work vehicle that spends its life loaded.

If your truck runs the Caprock regularly — Post, Justiceburg, the 82 grade east of Crosbyton — that is a reason to have brakes checked on a shorter interval than a town vehicle. We come to you and measure them. Call and we will schedule it around the vehicle rather than around a shop bay.