Getting your RV down a steep grade safely is an art that we all need to perfect. If you’ve hit the bottom of a long, steep grade and seen an RV beside the road, smoke pouring out from the wheels, you may have muttered something about the “Grace of God.” So, just how do you make the grade on the downhill side?
Old trucker’s maxim
First, remember the old trucker’s maxim: You can go down the hill too slow many times. You can go down the hill too fast only once. Why is it so?
A quick review of physics helps. Brakes work by causing friction (between the brake pads and the rotors or drums) to create heat. That brake action converts kinetic energy (movement) into heat energy. How much heat is produced is a factor of how heavy your rig is and how much speed you need to scrub off with your brakes.
Here’s the rub: If you convert too much kinetic energy into heat energy too fast, your brakes will fade, losing their ability to slow you down. There are two causes of brake fade. One is when the brake linings get so hot that gas builds up between the brake lining and the rotor or drum. The brakes “feel” like they ought to be working, but the ability to scrub off speed is reduced. Smoking brakes are common here. The other cause of brake fade is also heat related. When the system brake fluid gets too hot, it begins to boil. That causes a loss of pressure between the brake pad and the drum or rotor. The brakes will feel “spongy,” and typically your heart feels a bit heavy in your chest.
Controlled braking
To keep your rig under control, how you shake off heat from your brakes can make a big difference between making a slow, controlled descent, or one that could be your last. Back when we were kids in driver education (a few ages ago) we were taught, “When you go downhill, step on the brakes lightly, and keep the pressure on until you get to the bottom of the hill.” This is the so-called “controlled braking” method. The theory behind controlled braking is that brake heat is never built up suddenly, but in a gradual fashion.
If you learned this in driver’s ed, you are showing your age. It’s an interesting theory, but one that could prove DEAD WRONG. Here’s the problem with controlled braking. Heat does build up, and maybe gradually. But on a long grade, the brake materials are constantly producing heat, and never allowed an opportunity to cool. Without a cool down, the result is damage to the brake system and, ultimately, failure. If one brake in the system isn’t doing its fair share of the work, the rest of the brakes in the system have to take up the slack, adding even more heat to the mix.
For tractor/trailer combinations, this is an even more critical issue, as the physical design of the system uses a network of valves that use air to actuate the brakes. If the valves are not all set to the same pressure point to actuate, this imbalance may cause some brakes to operate by using a light application of the brake pedal, while other brakes aren’t working at all.
Snub braking is better braking
Throw out the old-school controlled braking. Try “snub braking.” On the downgrade, snub braking says you downshift appropriately, use an engine brake (if equipped), and have in mind the maximum safe speed for the grade. Reach that “maximum speed” and apply the brakes hard. Drop the speed by five miles per hour. Now let off the brakes and coast, keeping an eye on the speedometer. When the maximum safe speed is hit, repeat the process.
Snub braking theory is that while the same amount of heat energy needs to be created to slow down the same amount of weight, the time between “snubs” allows the brake system to cool down. Chances for brake fade drop.
For air brakes, snub braking, by its “hard on the pedal” nature, forces all the valves in the system to open. That makes it more likely all brakes on the rig do their fair share of braking. Depending on their brake controller, RVers who tow may find their trailer brakes actuate more in tune with the tow vehicle with a snub brake. That means a better share-the-load situation.
Brake maintenance
Snub braking doesn’t make up for bad maintenance or “pilot error.” The boiling point of brake fluid is reduced when it contains contaminants. Brake fluid essentially attracts water. Water in brake fluid is a combination that can spell disaster. Don’t keep the cap off the brake fluid (or the vehicle’s fluid reservoir) any longer than necessary when servicing brakes.
Moisture will just naturally find a way to worm its way into your brake fluid, even when you’re a “careful capper.” That means doing brake fluid changes as your owner manual suggests. If your rig “lives” in a humid climate, more frequent fluid changes are best.
A brake fluid tester can take away the guesswork. You can get one for about $10 (here’s one from Amazon). We got one, and it’s simple to use. Just dip it in the brake fluid. Indicator lights tell you where you stand.
Keeping those brake pads and drums or rotors up to snuff is critical. Trailer towers, this means a regular maintenance routine. If your trailer axles are equipped with an “easy lube” system, forgo the “easiness.” Jack the rig up, pull off the wheels, and inspect the brakes. Repack your wheel bearings at the same time.
Make sure your brake controller is properly adjusted – both the tow vehicle and the trailer should share the load. Drag out the owner manual and educate yourself on how to properly adjust the system. Did your manual vanish? Google-search it: You’ll likely find the instructions on the web.
Pilot error
As to pilot error: That old trucker’s maxim applies to RVers of any stripe, be they motorhomers or dyed-in-the-wool fifth-wheelers. You can’t go down a steep grade too slowly. Keep in the slow lane, drop down the gears, and use common sense. The faster you drive, the more heat you’ve got to scrub off to slow the rig down to a comfortable zone. If you use the snub system and find you’re having to snub your brakes every few seconds, you’re going too fast. Drop a gear, drop the speed, and get to the bottom with a smile on your face.
##RVDT2434
When I was pulling my 33’ 7 ton fifth wheel, I would do the snub (I called it stab) method but also put my flashers on as I descended warning traffic I was coming down slow.
For some odd reason it’s illegal in Florida to use your flashers while in motion. That said, if I see a car coming up in my rear view mirror at what I consider an unsafe speed I turn them on anyway.
I learned long ago to go down a hill in the same gear you go up a hill…for starters. If the hill,or mountain, is steeper going down than up…stop at the top and do a brake check and proceed in the lowest gear,within reason,with common sense. Learn what a truck run away ramp is for also…it may save your six some day.
Going down a hill in the same gear you went up in no longer applies with the greater horsepower available in recent years. I just came through the Rocky Mountains and with my 5th wheel I gross out at 25,946 lbs. My Ford F350 with 475 horsepower can climb any hill in 7th or 8th gear in my 10 speed transmission. Coming down the same grades and in 3rd gear I still had to snub the brakes several times which would drop my RPM from 3800 to 2800.
I am “lucky” to have an engine brake equipped truck to pull our 35′ 5th wheel. On steepish downgrades, I slow to 10 mph BELOW the maximum posted limited and let the engine brake control my speed, which will usually be about 5-7 mph faster than the cruise control set speed.
Seldom do I ever use my truck or trailer brake to control the descent. No white knuckle drives for me!
I have a Curt, Spectrum Brake Controller the GMC dealer installed. Worst break controller I ever had. Can’t figure the proper way to adjust the electric brakes and dealer just shrugs things off when I complain. Curt won’t even respond back to me after I emailed them twice. Will never buy another truck without a factory installed break controller.
I’ll add 2 more very important points (I’ve been teaching CDL training for 37 years).
#1 Pay attention to not only the steepness of the grade, but also the length of the grade. The steepness tells you how HARD you’ll have to brake, the length tells you how LONG you’ll have to brake. Both are very important in calculating your “safe” speed for decent.
#2 If you need to pull over to let the brakes cool, do NOT apply the parking brakes. Chock the wheels instead. This allows the parts cool faster and eliminates brake damage.
BTW, the term is “Driver Education” not “Driver’s Education.”
In addition to pumping the brakes when going downhill, I find that my F250 does an excellent job of assisting by down-shifting when in tow/haul mode.
Thank you, Russ and Tina! 🙂 We have a rather steep, but not especially long hill that we routinely drive. I pump the brakes every few seconds and release when I descend. Thereby the vehicle speed fluctuates between a desired speed (achieved by braking) and an acceptable speed (beyond which I again apply braking). I guess this is the “snub” method, but I did not have a name for it. When traveling through hills or mountains (typically our eastern ones) in the RV, I activate the “engine brake,” which downshifts the transmission to second gear until I apply throttle. I rarely have to apply the brakes as well. Thanks again, have a great day, safe travels, and safe stays! 🙂
No one needs to speed. Interstates are the only highways with minimum speed limits. Driving 5 mph under the speed limits and lifting your foot off the accelerator IN ADVANCE of the need to slow or stop will greatly increase your brake life
What about engine braking?
All I need to do is hit one switch, and the engine kicks back, slowing the coach to a crawl without the use of the service (air) brakes.