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.

If your pedal has felt soft on a descent this summer, have the fluid tested before it happens again. Call Knoxville Auto Repair on (865) 606-6602 — we're on Lovell Road in West Knoxville, open 9 AM to 5 PM Monday through Friday.