Descending US 441 from the Great Smoky Mountains to Cherokee, there’s a set of steep hairpin curves. After the last 180-degree turn, it’s a mostly straight 4-mile run from 4,000 feet of elevation to 2,700 feet at the Kephart Prong Trailhead. Near the trailhead you’ll notice a weird metallic burnt smell. It’s from brake pads.
Unassuming motorists drive those miles standing firmly on the brake pedal. Entering Cherokee, North Carolina another 8 miles down the road, the brake pedal feels firm, but nothing much happens anymore when it’s pressed. Smoke may be rising from both front wheels.
To avoid this overheated brakes condition, which is expensive to start with and can be life-threatening in a crash, it’s important to know how brakes work. As the vehicle travels downhill, it gains forward momentum, or kinetic energy. Energy can’t be destroyed, only converted into something else. We convert it into heat by applying friction to a rotating metal disc (the brake rotor). Two metal pads with a special lining squeeze the rotor from each side. This rubbing effect on the rotor slows the car and generates a lot of heat. But there’s a limit to how much heat the pads can handle. In a family car full of people and luggage, or a pickup truck towing a camper, the heat limit is reached easily on US 441 descending into Cherokee. When brake pads overheat, their friction lining softens and begins to melt. This makes them lose their braking power, and it can turn out to be difficult to stop for the pedestrian crossing at the Mountain Fun Gem Mine and Teepee Gift Shop. Do-it-yourself car mechanics can buy a pair of replacements for warped rotors, burnt pads and ruined calipers for about $400 to $900. As a repair job at the dealership, it’s likely to go well into the 4 figures.
Preventing brake fade is easier in a car with manual gearshift, or on a motorcycle. Shift into low gear and let the engine do some of the braking. In an automatic, I like to brake and slow down more than needed in each curve, then let the car slowly build momentum again until the next one. It also helps to take a shopping break and enjoy some Cherokee souvenirs while letting the wheels cool down before continuing on the rigors of US 441.
Rudi Kiefer, Ph.D., is a professor at Brenau University, teaching physical and health sciences on Brenau’s Georgia campuses and in China. His column appears Sundays and at gainesvilletimes.com.