Excellent points. One more thing---if the brake fluid isn't fresh and very low in water content, the heat from hard braking can cause any moisture in the fluid to flash to steam. Your pedal goes to the floor and you have no braking. Keep your brakes cool by downshifting on long steep downgrades.
Originally Posted By: jaj
If you're doing a long, steep descent (we have a bunch within about four hours of where I live) you should disengage overdrive or drop the transmission by one gear - RPM should maybe rise to 2500RPM or so. You want additional braking; it's there to help, not to do the entire job. Then use the brakes to keep the speed under control: pick a max speed slightly faster than traffic and a slow speed slightly slower. When the car coasts to the max speed, slow it down to the minimum speed with a firm brake application, then release the brakes and allow it to coast back up the to max again. This will keep your brakes from overheating. What you're avoiding is brake fade or failure. If you just hold your foot on the brake to control the speed, heat just keeps building up and up and up until the pads fade or the fluid boils. This is because the pads stay pressed on the disks, and heat transfers from the disk through the pad to the caliper. The longer you hold the pedal, the hotter the whole assembly gets. However, if you brake and release, the rotor temps spike up more but they're cast iron, so they don't care. What matters is that between applications, the calipers aren't pressing the pads against the rotors. Heat transfer stops and they get a chance to cool down between applications; they're less prone to overheat.