Safely Descending Hills In EV or ICE Vehicles

Have you ever driven down a steep hill and then started smelling something awful? Whether the smell is coming from your car or it’s coming from somebody else’s, the unmistakable smell of brakes being cooked is extremely unpleasant. But, it’s a lot more than just bothersome—it’s a sign that somebody’s life is literally in danger!

Sadly, there are many people who don’t know how to avoid this smell. Worse, there are even people who actively share bad advice that can readily put someone in this position, sometimes even in the name of efficiency.

Before you scroll down to the comments or look me up to send me a nastygram, I already know that EVs basically solve this problem. Instead of having to know what you’re doing to avoid overheating your brakes and sending yourself on an unplanned trip off a cliff, you can simply use regenerative braking and get some of that energy back while going down a steep hill. But, surprisingly, even EVs sometimes require the driver to do the right thing at the right time.

So, I’m going to do a quick PSA about this topic so that readers both in ICE vehicles and in EVs can reduce their chance of destroying a set of brakes and possibly die.

Both Engines & Motors Can Slow You Down

If you’re an EV owner and you keep your vehicle on a strong regenerative brake setting, the answer to a steep downhill grade is obvious. Just let the electric motor do the braking, right? But, sadly, there are some situations where some EVs won’t do this correctly. Strangely, my Bolt EUV is one of those EVs. When in one-pedal drive, it will give over 50 kW of regen, and take care of even a trailer load of deceleration. But, if I turn the cruise control on, the thing will use the brakes to slow down on hills, which isn’t great for range or brake life. A Nissan LEAF I used to own would sometimes apply the brakes on downhills stretches to heat them up and dry them out, but sometimes that happened at the wrong time (like a 4,000 foot descent).

Plus, not everyone knows that you need to activate strong regenerative braking to get the kind of automatic speed control you’d want in any EV. So, educating people on how to avoid getting into the friction brakes is still important.

ICE vehicles are also very much capable of slowing you down when going down a steep hill. By putting the vehicle in a lower gear or using tow/haul mode, the engine’s compression (air getting squeezed in the cylinders) converts kinetic energy into heat, which is harmlessly dissipated by the vehicle’s radiator.

There’s no downside to using compression braking (aka engine braking) because modern fuel injected vehicles completely cut off the fuel during deceleration. In fact, there’s a small benefit, as the rotational forces the engine is going through still turns the alternator, charging the vehicle’s 12v battery while not using fuel. The heater still works, the air conditioning compressor is getting turned, and vacuum used to run the power steering and brakes is still there. So, you get all of the safety and comfort features of your ICE vehicle without expending any fuel or creating any emissions!

When Regen or Engine Braking Doesn’t Cut It

Sometimes, there isn’t enough regen or engine braking to control your speed going down a hill, and you still have to use the brakes a little. This happens more often when towing. But, even then, you still need to be smart about brake use. A constant light application of the brakes is still likely to glaze the surface of the brake pads and/or heat up the brake fluid, and either of these things can reduce or destroy your ability to stop in time.

To avoid this, pump the brakes. Give a nice, firm push to the brake pedal and slow down more than you ideally would want to. Go perhaps 5 MPH below your target speed. Then, release the brakes to give the system time to cool off. When you’re 5-10 MPH over your target speed, do another firm push to quickly reduce speed back to 5 MPH under the target. By doing this in surges, the system has adequate time to cool while you still maintain control over your speed.

Featured image: A backroad suddenly drops down a steep incline into New Mexico’s Tularosa Basin. White Sands National Park can be seen in the background. Photo by Jennifer Sensiba.