Brake Fade Coming Down From the Smokies: What It Feels Like

The complaint arrives the same way most summers. Someone drives up to Gatlinburg or over Newfound Gap, spends the day, and on the way back down the brake pedal goes long and soft — traveling further than it should before the car slows. By the time they reach Sevierville it feels normal again, so they put it out of mind.

That is brake fade, and the reason it comes back to normal is the reason it is worth understanding. Nothing broke. The brakes got hot enough to stop working properly, then cooled down.

Why a long descent does this and city driving doesn't

Braking converts motion into heat. In town you brake hard for a few seconds and then roll, and the discs shed that heat between stops. Coming down a sustained grade you are braking almost continuously for several miles, feeding heat in faster than it can escape. Pads lose bite as they overheat, and if the fluid gets hot enough the moisture in it can boil, putting compressible vapor into a system that only works because fluid isn't compressible. That is the soft pedal.

It is not a fault with the car. A vehicle that behaves perfectly on Kingston Pike will still fade on a long enough descent if it is held on the brakes the whole way down.

What to do on the mountain

Use the engine. Drop to a lower gear — on an automatic, that means selecting a lower range rather than leaving it in Drive — and let engine braking hold the speed while the brakes cool. If you are already fading, find somewhere safe to stop and let them cool properly. Ten minutes stationary does more than any technique.

What does not help is riding the brakes lightly the whole way. A constant light drag keeps feeding heat in with no chance to shed it, which is the worst case for both pads and fluid.

What to check afterwards

Brake fluid is the part people skip. It absorbs moisture out of the air over time, and moisture is what lowers its boiling point — which is why an older car fades sooner than a newer one with identical pads. Fluid that has never been changed on a car that regularly runs the Gatlinburg and Pigeon Forge roads is worth testing.

Then the pads and discs. Repeated overheating glazes pad material and can leave discs unevenly heated, which shows up later as a pulse through the pedal. Caught early it is a pad and disc job; ignored, it becomes a longer one.

The pattern we see from customers in Sevierville, Pigeon Forge and Gatlinburg is not worn-out brakes. It is brakes that have been cooked a few times and never checked since.

Telling fade apart from a real fault

Fade recovers. That single characteristic separates it from most of the things it resembles. A pedal that went long on the descent and feels normal again in the valley was heat, and the system is intact.

A pedal that stays soft after everything has cooled is a different matter. Air in the lines, a failing master cylinder, or a leak somewhere in the hydraulics all produce a long pedal that does not come back, and none of them improve with rest. If the car sat overnight and the pedal still travels further than it used to, that is not fade and it should not be driven on casually.

A pedal that sinks slowly toward the floor under steady foot pressure at a stoplight points at the master cylinder specifically. Watch for a brake warning lamp and check the reservoir level, because a level that has dropped without the pads being worn means fluid has left the system.

The technique that works on a long grade

Choose a gear before the descent rather than after the brakes are already hot. On most automatics that means moving out of Drive into a lower range or using the manual mode, and the right gear is the one that holds your speed with little or no pedal at all.

When you do need the brakes, use them firmly for a short period and then release fully. That approach lets the discs shed heat between applications, whereas a constant light drag never gives them the chance. Racers call it snubbing and it is the opposite of what most drivers do instinctively.

Vehicles pulling anything need a gear lower still. A trailer adds mass without adding braking capacity on the tow vehicle, and the descent from Newfound Gap is not the place to discover the difference.

Have the fluid tested before the next descent rather than after. Knoxville Auto Repair answers at (865) 606-6602; the shop sits on Lovell Road in West Knoxville, weekdays from 9 until 5.