Mountain driving
Updated 12/15/2019

Driving in the mountains can be exhilarating, as new vistas unfold with each curve in the road. It can also be a "white-knuckle" experience, and potentially a fatal one.

10% grade

A few weeks ago I was driving down a mountain with a friend. As we passed a sharp curve, she pointed to where the guard rail had been repaired, and told me that a family from Kansas had recently died at that spot (or more accurately, several hundred feet below it). They were coming down the mountain, riding the brakes as flatlanders will do... until the brakes gave out, they failed to make the curve, and went over the edge. They didn't know to downshift. If they had started down that grade in low gear, they'd still be alive, instead of splattered across a rocky ravine.

This kind of accident is all the more tragic because it's completely avoidable. If you know just a few simple tricks, you can cruise safely over the steepest hills. Read this article, and you'll know how.

Mountain Directories

Pick your roads

The best way to avoid problems is to avoid steep roads. Well, that's easy to say—but how do you know which ones are steep? There are a couple of books that tell you: Mountain Directory East and Mountain Directory West.

Written especially for truckers, but equally valuable for RVers, the Mountain Directories will help you plan a route that avoids the steepest up- and downgrades... and they'll prepare you for the ones you do encounter, so you won't be taken by surprise. These books are out of print, but still invaluable, so pick up a couple of used copies while you can!

Check the weather

One warm, sunny June day, a friend and I set out to drive up Pike's Peak. But about halfway up the mountain we were stopped by a barricade. The road to the summit was closed, due to heavy snow the day before.

Mountains have their own climates. Always check the weather before starting out on a high-altitude adventure. If you don't, you run the risk of being stopped by unexpected bad weather—or worse, caught in a mountain pass, unable to go down because a snowfall has blocked the roads behind you and ahead of you.

Up the hill

Most cars can go up a fairly steep grade without slowing down. Most RVs can't. On a 6% or greater grade, your RV probably won't have enough power to maintain a steady 60 mph. That's OK, as long as you know what to expect and don't get impatient. Let your rig slow down naturally. Shift to a lower gear (or "kick down" your automatic transmission) to take some of the strain off the engine. If your speed drops below 40 mph, it's courteous to turn on your four-way flashers. (It also greatly reduces your chance of being rear-ended by a fast-moving vehicle.)

A/C button

Turn off your air conditioner—it puts an additional load on your engine, and when you're hauling several tons of RV up a steep grade, you don't need that.

Watch your engine temperature. If the temperature starts to climb into the danger zone, turn on your heater. It may sound counterintuitive, but the heat that fills your cab is heat pulled away from your engine. Then look for a place to pull over and let the engine cool off for twenty minutes or so.

And one more thing: if your engine does overheat and start to steam, DON'T REMOVE THE RADIATOR CAP! (Assuming you have one, that is.) I saw this done once. The guy who did it was so badly scalded by the resulting burst of steam that he had to be flown by helicopter to a hospital for burn treatment. Don't make this mistake! The only cure for overheating is a long cool-off period.

Downshift before descending

OK, you've topped the hill at last. The hard part is over, right? Wrong. Now comes the part where you really have to know what you're doing: maintaining your speed on the downhill slope. "No sweat," you say, "I have good brakes." But you're going to need more than brakes to make it safely to the bottom.

When your vehicle is going 55 or 60 mph, it has a lot of kinetic energy. When you want to slow down, your brakes convert some of that energy into heat. If you keep your foot on the pedal for more than a few seconds, your brakes get quite hot.

Now, brakes are meant to withstand heat, up to a point. But when they get hot, the hydraulic fluid that transmits the force of your foot to the brakes gets hot too. And if it gets hot enough to boil... well, those bubbles are compressible, so they don't transmit your foot pressure to the brakes. Your brake pedal feels spongy.

At that point, you've lost your brakes. It doesn't matter how hard you press; you aren't going to slow down. The emergency brake? Go ahead and try it... but once you're moving that fast, it won't stop you. You're going to go faster and faster, until you run off the road.


The solution is to use your engine to slow you down. When in low gear, it has tremendous slowing power—and unlike your brakes, it won't overheat and lose its ability to slow the vehicle. Folks who are used to driving stick shifts know this already, but most RVs have automatic transmissions, and most RV drivers aren't in the habit of using anything but "D." But did you ever wonder why your automatic transmission also has "L" (low) or "1" and "2" settings? This is what they're for. Those lower gears can slow down your vehicle without burning up its brakes.

But here's the crucial thing: you must downshift before your speed becomes excessive. If you wait until you're careening down the mountain at 70 mph with nonworking brakes, you probably won't be able to get the transmission into low gear. The place to downshift is at the top of the slope, before you really get going. If you do that, your speed will never get out of control, and you'll only have to tap the brakes briefly once in awhile.

Here's a real-world example: driving a 7-ton motorhome and towing a car, I came down US 82 from Cloudcroft, NM—a 17-mile-long 7% grade that's liberally supplied with huge warning signs, runaway truck lanes and the like—and only tapped my brakes a few times, for a total of less than 20 seconds. (Yes, I timed myself.) I did it in second gear. It was easy.

Brake on the straightaways, coast through the curves

When you must use your brakes, try to do it on a straight stretch of road. You're much less likely to lose control while braking in a straight line than when making a high-speed curve. (This is also excellent advice for driving in icy, snowy, or wet conditions, by the way.) And when you do brake, slow down more than you need to, so you can coast through the curve at a safe speed.

Let's say you're going 60 mph down a straight stretch, and you see a sign warning of a 45 mph curve up ahead. Use your brakes to slow down to 40 while you're still on the straightaway, then coast through the curve. Of course if your speed creeps up dangerously in the curve, you should use your brakes there... but try to plan ahead so that you don't have to.

Stop and cool off

If you notice the slightest touch of sponginess in your brake pedal, find a safe spot and pull over for ten or fifteen minutes to let your brakes—and that all-important brake fluid—cool off. Get out and look at the scenery. Relax. Give your brakes plenty of time to cool, because sponginess means you're about to lose your brakes completely, and that can easily be fatal.

Go down like you came up

Here's an easy-to-remember rule of thumb: go down a hill in the same gear you climbed it. If you have to drop into second gear to climb a steep one, then you should go down the other side in second.

For example, I once descended into Palo Duro Canyon State Park in Texas, driving a motorhome heavily loaded with boxes and towing a car with nearly half a ton of books. (I was returning from cleaning out my storage room in New Jersey.) The road down into the canyon is a 10% grade, with plenty of hairpin turns and switchbacks.

Palu Duro winding road

I took it in first gear without any problems, tapping the brakes briefly just before the hairpin turns. When I left the park, I drove back up the road in first gear, again with no problems.

Toad brakes are a must

One reason I had no problems with that 10% grade was that my towed car was fitted with a good auxiliary braking system. If you're towing a car, you need auxiliary brakes. Otherwise you're asking your motorhome's brakes to do a job they were never designed for: stop an additional ton or two of vehicle mass. You wouldn't load your RV to a couple tons beyond its capacity, right?

That's why "toad brakes" are required by law in most US states and all Canadian provinces... and required by common sense everywhere. For more on outfitting a car with auxiliary brakes, see my article "Follow the Leader."


That's really all there is to it: avoid steep roads if you can; check the weather; downshift before descending; brake on the straightaway; and stop and cool off. Remember these simple tips, and you'll have a safe and enjoyable trip, instead of a white-knuckle ride to disaster.

"Eureka!" is © 2012 by Andy Baird.