Downhill Braking Advice

[Gibson3798]

A preface: I’ve driven many types of heavy trucks carrying sizable loads.

Question: Given my experience with those, I’ve never pulled a trailer down steep mountain downgrades. I keep reading that riding the brakes should be avoided, which I understand, but I’d like advice on how to avoid that and still keep the trailer (25ft. FC) slowed down.

My TV is a 2015 Toyota Tundra 5.7 w/tow package, with a Reliance brake Controller.

Thanks!

[ROBERT CROSS]

I put the Burb in 4wd and use the transmission and Hawk Pads on all four corners. (best perf pads I've used)

Bob
🇺🇸

[markdoane]

I'd use they same incremental method you use when hauling a semi trailer. Use the truck brakes and the trailer brakes together. Watch out for overtaking semis. Be prepared to manually heavy up the trailer brakes if it starts to get "pushy".
Let the speed increase about 10 mph while the brakes cool, then apply the brakes until you've slowed down by 10 mph. Drum brakes are more susceptible to fade than disks, so plan accordingly.
Of course use the appropriate drive ratio and watch your rear view mirrors.

[GettinAway]

Second gear on steep downhill mountain passes, and I slow down “before“ I get to the downhill. The rpms make me cringe, just from the sound, they really aren’t that high. Have been over many many passes in CO. No trouble. I’m pulling a 25’ with a tundra.

Edit, just an FYI, you may have opened up a can of worms. The diesel folks will be jumping in shortly. It is easier to use a Diesel engine brake. I’m sure you already know that, as do we all.

[Al U. Minium]

1. Keep your speed under control. Don't let it get too high just because there is a long straight stretch.
2. Brake in a straight line. Reduce your speed before you get to the curve.
3. Don't be afraid to use your brakes. Modern vehicle brake systems are robust. Brake pads are a consumable. Pads and rotors are cheap and easy to replace.
4. Brake smoothly and decisively. Don't slam them on. Back to number 1, keep the speed under control and avoid the Oh poop pants! moments.
5. Have your trailer brakes adjusted. Test them every time you have a rest stop.
6. If your truck has a grade brake feature, these really help with item 1. Keep your speed under control. Pick a speed and keep under it. A suggestion is something 5 to 10 mph UNDER the posted limit, or if a truck speed limit is posted, use that.
7. Don't be sorry for anyone behind you. Ignore them, they can go around or wait for the bottom of the hill.
8. Stay in the right lane.

[OTRA15]

Good advice already.

In the "very unlikely possibility" department . . . . . . be ready to apply the trailer brakes manually with your controller, if there is any sway or trailer-breakaway issue, perhaps because of high winds, sand or ice on the road, and so forth.
[Edit -- echoing Mark's suggestion -- "manually heavy up the trailer brakes"]

Always good to prepare one's possible emergency moves ahead of time.

With your trucking experience, Gib, this is probably going to be second nature for you IMO.

Happy trails,

Peter

PS -- Similar earlier threads FYI: https://www.google.com/search?q=down...=airforums.com

[BayouBiker]

For anyone who finds they have to use their brakes very frequently and they get very hot, purchase cross drilled brake rotors. Avoid cross drilled and slotted, as the slots shave a bit of the pads off for optimal race track braking so you may have to replace pads twice as frequently if you get slotted rotors. Cross drilled rotors will run 20-50 degrees cooler.

[Bill M.]

When pulling a trailer with electric brakes I think it is better to "pump" the brakes on a descent instead of just applying them partially for a long time. I do not want to overheat or catch the trailer brakes on fire and I do not think they really work "proportionally" on a long downhill.

[Dan and Liz]

Originally Posted by GettinAway

Second gear on steep downhill mountain passes, and I slow down “before“ I get to the downhill. The rpms make me cringe, just from the sound, they really aren’t that high. Have been over many many passes in CO. No trouble. I’m pulling a 25’ with a tundra.

Don’t worry about keeping up to the speed limit. If you’re in the right gear, you shouldn’t need to brake so much that you’ll overheat. And if you need to brake, do it before (not in) a curve so you enter at a comfortable speed.

[Al U. Minium]

This is one area where 3/4 ton trucks have significant improvements and upside.

They have huge rotors (and multi cylinder calipers) --even the back brakes.

In brakes, rotors are your heat sinks. Yes, they are vented and you can cross drill for air flow dissipation, but the big advantage of big rotors is they take longer to heat.

When brakes overheat, it usually isn't the pads or rotors that get you in trouble. It is water in your hydraulic fluid that gets over 212F and turns to bubbles. Now you have problems compressing the caliper cylinders. Brake fade. Pedal goes to the floor in the worst case you go agricultural instead of making the curve.

So, the lessons here are: change brake fluid per maintenance schedules. And per Bill M.'s good advice, don't ride the pedal, slow down and then get off the brakes. But, use your brakes and control your speed. Slowing down 3mph is preferred over slowing down 20mph, and doesn't put as much heat in the rotor.

Spent lots of time on the road course track learning about how brakes fail. Was a high speed driving instructor and racer for a number of years.

[polarlyse]

We're east coasters but travel a lot out west and, like the rest of us out there, often need to navigate the steep grades. I have a diesel pickup and find I can go up these mountains with ease and passing most everyone on the uphill grade. But, then the fun comes of going down the other side. Remember, what goes UP must come down. Sometime. After a long uphill grade I will often take a break at the top, if there's a place to park, and let my truck cool down a bit. Then I begin the downhill at a very conservative pace. I find a speed that is easy to maintain. My truck ( Ford F-350) will always find a sweet spot that between the transmission and exhaust brake is easy to maintain. Often that's around 35 mph and I just let it do it's thing. In doing this I find I rarely even need to apply the brakes.

That's my story and I'm stickin to it.
Hope ya'll are healthy and virus free. See ya on the road sometime.

[kscherzi]

I've found that pumping brakes on long downhill stretches tends to cause the trailer brakes to be under applied. Reason is there's a time lag between pedal pressure in the truck and full application of the electric trailer brake. Maybe just a second or so, but it adds up if one is pumping.

I learned this coming off Towne Pass from Death Valley, a nine mile long 6% to 9% constant downhill. Had to pull over as truck brakes started to fade and were really hot. Checked the trailer wheels and they weren't even that warm. Proved the truck was doing all the work. Something else to think about.

[rmkrum]

One rule of thumb is to go down a grade at about the same speed and in the same gear you used when you went up that grade.

In my case, that usually means right lane, quite slowly, and giving way to trucks and other faster traffic. Some day I’ll get a Tundra to improve the rig’s climbing ability.

Until then, I’ll be very patient and polite.

[Mollysdad]

Originally Posted by Gibson3798

My TV is a 2015 Toyota Tundra 5.7 w/tow package, with a Reliance brake Controller.

I also have a 2015 Tundra, 5.7.
Here's what I do. First, don't get too fast that you need to bleed off speed. On downhills, I try to maintain 50 or so. Keep right.
On your shifter, if you press it to the left, it switches to manual and 4th gear. Paddle up to 5th, down to third. But 4th is a good starting spot. You'll be using engine breaking to maintain speed with a gentle tap of the brakes as needed. Watch the tach, the Tundra is so quiet, you can rev without noticing. I stay under 4500 rpm. Stay in "tow/haul" always.
Before you know it, you'll be through the downhill side!
I'm used to using the manual shift and I even use it as I approach slow traffic or stop signals, it won't shift into a lower gear if the RPM will be too high. It will beep. So you can't slap it into 1st at 30 MPH!

[Adventure.AS]

I find that using 'cruise control' helps keep the downhill speed under control. The TV computer downshifts as required and cuts off fuel flow to keep the set speed. If you use your TV brakes this turns off cruise control, so be ready to reset it if required. I also use the hand controller on the trailer brake controller to keep tension between the trailer and TV on steep sections.

[OTRA15]

Originally Posted by kscherzi

I've found that pumping brakes on long downhill stretches tends to cause the trailer brakes to be under applied. Reason is there's a time lag between pedal pressure in the truck and full application of the electric trailer brake. Maybe just a second or so, but it adds up if one is pumping.

I learned this coming off Towne Pass from Death Valley, a nine mile long 6% to 9% constant downhill. Had to pull over as truck brakes started to fade and were really hot. Checked the trailer wheels and they weren't even that warm. Proved the truck was doing all the work. Something else to think about.

What gear were you in and what was your speed? If you go slow enough, and choose a very low gear, it should be possible to tow the rig downhill without using the brakes that much IMO. Most current automatic transmissions let you manually downshift, so the old problem of runaway tow rigs [due to inadequate engine braking with automatic transmissions] is a thing of the past IMO.

The main "rub" is that prevailing downhill traffic may be going so fast, that your downhill "slower speed" creates a hazardous situation, but the point remains that "really hot" TV brakes should almost never happen IMO.

Emergency flashers on . . . pull over if necessary . . . no prob.

Peter

[pteck]

I live in the west and mountains and hills are the norm for the type of camping I like to do. In the summer especially, a great way to escape the heat is to go up in elevation. From which one must come down.

For a Tundra, here's the particular things to be aware of.

1) Engine braking. Use engine braking enthusiastically. You cannot over-use engine braking as it has infinite heat capacity. Downhill is all about bleeding off kinetic energy and translating it to heat energy. Of which engine braking is particularly efficient at translating kinetic into mechanical energy, and ultimately into heat that is transferred to the air pumped through it and into the cooling system.
- Don't be afraid of revs. The more revs, the more engine braking that is applied. Keeping it to some artificial limit, means you're not taking full advantage of engine braking available (and having to use more brakes). The computer will always keep it out of redline, but that's the only limit that should not be exceeded.
- Note that the Tundra, even in 4x4 guise, only drives the rear axle under normal on-road towing. That means the only engine braked axle is also that rear axle. Which is one axle among 4, for the overall rig.

2) Brakes. Don't afraid to use them and they are the safest most stable way to slow and stop the rig. That's because this is the only way that all 4 axles (and 8 tires) are engaged to slow down the rig (vs 1 axle and 2 tires with engine braking). Apply firmly in a single action when you need them. Don't ride/drag them or pulse them. If you're using engine braking appropriately like it's going out of style, there should be plenty of heat capacity in the brakes to use them when you need them.
- Even with engine braking, I generally always use brake to stabilize the rig before coming into a sharp turn. This is the only way to ensure the trailer is scrubbing it's own momentum (applying its own brakes) and not still surging/pushing on the tow vehicle as the rig takes a set to make the turn. Want the hitch to be in neutral without too much compression to minimize potential for jackknifing in a sharp turn.
- In poor traction conditions (i.e. rain), it's double important to use brakes for the reasons above coming into turns. Otherwise the rear axle of the tow vehicle is doing all the work and can exceed its traction circle by doing all the braking for the overall rig, and having to track into turns.

[BayouBiker]

As Al U Minum indicated, while braking, most of the heat from friction heats the pads, rotor and brake cylinder. Interestingly though a significant portion (most) of the energy to stop is used to "push" the earth in the opposite direction. Then as you continue to drive, airflow pumped into the center of the disk (the inner part of all front and many rear disks is an impeller) and radially outward and heat dissipating to the wheel and tire, cools the rotor for the next stop. A good go by is each 10 mph reduction in speed by braking warms the disks by 10 degrees or more depending on the rotor size. The Brakes start fading at about 450 degrees when the resin in the friction material smokes and gas gets trapped between the drum or rotor and the pad. If you haven't used your brakes in a long while you can figure they are about 125-150 . So if you use your brakes 30 times in very short order, they will likely fade. If you can extend that out to about 25-30 seconds in between they will be hot but won't overheat.

Hope this helps

[kscherzi]

Originally Posted by OTRA15

What gear were you in and what was your speed? If you go slow enough, and choose a very low gear, it should be possible to tow the rig downhill without using the brakes that much IMO. Most current automatic transmissions let you manually downshift, so the old problem of runaway tow rigs [due to inadequate engine braking with automatic transmissions] is a thing of the past IMO.

The main "rub" is that prevailing downhill traffic may be going so fast, that your downhill "slower speed" creates a hazardous situation, but the point remains that "really hot" TV brakes should almost never happen IMO.

Emergency flashers on . . . pull over if necessary . . . no prob.

Peter

Just looked it up, its a 9 1/2% grade for the first six miles, pretty substantial. Not to mention the 1,000 foot cliff off to one side. I tried to keep it under 35 mph, and in low gear, either 2nd or 3rd out of 10 gears. This is one situation where the 3.5 Ford ecoboost engine just doesn't have enough breathing capacity to give a lot of braking assist. I let it rev to 5,500 rpm even. Lesson I learned is to pump and hold, pump and hold, and be prepared to pull over before things get out of hand. Maybe I'll try first gear next time.

[Doc Foster]

Originally Posted by GettinAway

Second gear on steep downhill mountain passes, and I slow down “before“ I get to the downhill. The rpms make me cringe, just from the sound, they really aren’t that high. Have been over many many passes in CO. No trouble. I’m pulling a 25’ with a tundra.

Edit, just an FYI, you may have opened up a can of worms. The diesel folks will be jumping in shortly. It is easier to use a Diesel engine brake. I’m sure you already know that, as do we all.

Yes, slow down and downshift before you crest over that mountain pass. Never let your speed get out of control. Use breaks when you have to, but downshift.