How to drive down a mountain pass without cooking your brakes
The smell of hot brakes halfway down a pass is your car asking you to change technique.
Every summer, thousands of European drivers point a fully loaded car down an Alpine or Pyrenean pass for the first time, rest their foot on the brake pedal for ten kilometres, and arrive at the bottom with a pedal that has gone soft and a smell like burnt toast drifting through the vents. Nothing has broken. The brakes have simply been asked to do a job the gearbox should have been sharing. Getting a heavy car down a long descent safely is a technique rather than a strength contest, and it takes roughly one hairpin to learn.
The short version
Brake fade on a long descent is overheating, not a fault: the pads lose bite and the brake fluid can boil.
The fix is technique, not strength: descend in roughly the same low gear you would need to climb the slope.
Let engine braking hold the car continuously, and brake in firm, short presses rather than riding the pedal.
It matters most with a fully loaded car on a long Alpine or Pyrenean pass.
What brake fade actually is
Brakes work by turning movement into heat. On a flat road that heat has plenty of time to blow away between stops. On a ten-kilometre descent with a full boot, you feed heat into the discs continuously and give them nowhere to dump it. Two things then happen. The pads lose bite as their friction material overheats, and, more seriously, the brake fluid can start to boil inside the lines. Vapour compresses in a way that liquid does not, so the pedal sinks further toward the floor while achieving less and less. That is brake fade, and it arrives with very little warning if you have never felt it before.
Let the engine do most of the braking
The single most useful rule for any descent is to go down in roughly the same gear you would need to climb the same slope. In a manual that usually means second or third, not fifth. Engine braking uses compression to hold the car back continuously and for free, without generating a gram of heat in the brake discs. In an automatic, select the manual or sport mode, or pull the left paddle a few times, until the car settles at a steady speed with your foot off everything. If the engine sounds busy, that is the point. A high-revving engine on a descent is doing exactly what you want it to do.
Brake firmly and briefly, never lightly and constantly
Dragging the brakes gently the whole way down feels careful and is the worst thing you can do, because the pads never leave the discs and the heat never stops building. The better method is to pick a target speed, let the car creep a few km/h above it, brake firmly for two or three seconds to bring it back under, then release completely. Those gaps with the pads fully off are what let airflow carry the heat away. And never coast down in neutral or with the clutch held in to save fuel. You lose all engine braking, you lose the ability to accelerate out of trouble, and a modern car already cuts fuel to the injectors on a trailing throttle, so there is nothing left to save.
A loaded car changes the maths
Four people, a full boot and a roof box can easily add 400 kg to what your brakes have to slow down, and a caravan or trailer multiplies that again. Every extra kilo becomes extra heat at the bottom of the hill. Towing anything means dropping one gear lower than you otherwise would and starting the descent slower than feels necessary, because once the discs are hot there is no quick way to cool them while moving. It is the same hot-weather logic behind checking your coolant before a long summer trip. The systems that manage heat in your car have the least margin exactly when you are asking the most of them.
Read the road, not just the next corner
Alpine passes are signposted with their gradient for a reason. A sign reading 12 percent tells you the descent is steep enough that momentum will build faster than you expect between hairpins, so choose your gear at the top rather than halfway down, when you are already carrying too much speed to select it cleanly. Keep a larger gap to the car ahead than you would on the flat, because on a descent everyone's stopping distance grows and the driver in front may be someone discovering brake fade for the first time. If a queue forms behind you, use a pull-off rather than raising your speed to keep up. Slow and cool beats fast and popular.
Electric cars are brilliant at this, with one catch
An EV descending a pass is close to ideal. Regenerative braking holds the car back using the motor, generates no disc heat at all, and pushes energy back into the battery, so it is entirely normal to reach the bottom of a long descent with more range than you started with. Select the strongest regen setting, or B mode, before you begin rather than partway down. The catch is that a battery cannot absorb energy it has no room for. Start a fifteen-kilometre descent at 100 percent charge and the car will taper regen away to almost nothing partway down, quietly handing the work back to the friction brakes at the worst possible moment. On a mountain day, leave the car at around 80 percent before a big descent and let the road do the rest of the charging. That extra battery weight is also why EVs are harder on some components than a comparable petrol car, which we looked at in our piece on EV tyre wear. If you are shopping for something to take on next summer's trip, you can browse the latest listings on AutoNext.
Frequently asked questions
How do I know my brakes are overheating?
A sharp, acrid smell, a pedal that travels further than usual, and a clear drop in stopping power are the classic signs. If you notice any of them, find a safe pull-off, stop, and let the brakes cool for at least fifteen minutes with the car in gear or in Park and the handbrake off if the ground allows. Never throw water on hot discs, you risk warping them.
Does engine braking damage the engine or gearbox?
No. Both are designed for it, and on a trailing throttle most modern cars cut fuel entirely, so you are using less than at idle. The only thing to avoid is downshifting so aggressively that the revs jump past the red line, which most cars will refuse to do anyway.
Should I use cruise control going downhill?
Generally not on a steep pass. Standard cruise control cannot brake, so it simply lets the car accelerate away down the slope. Adaptive systems will use the brakes to hold speed, which is exactly the heat you are trying to avoid. Take manual control on anything long or steep.
How often should brake fluid be changed?
Most manufacturers specify every two years regardless of mileage, because brake fluid absorbs moisture from the air and moisture lowers its boiling point. Old fluid fades far sooner than fresh fluid, and a mountain descent is exactly the road that exposes the difference. Worth checking the date before a summer trip south.
