Best practice for steep downhill freeway grade

[ZachO]

A good thing for people to understand if they've never had it happen- if you ride the brakes downhill, they will overheat, the brake fluid will get so hot that it loses its ability to force the brakes to work anymore (essentially turning from a liquid to a gas (or at least that's how people describe it, not sure if that's technically true)), and so the brakes stop working. Pedal goes straight to the floor.

This can (and should) be pretty scary, but if you experience it, don't panic. They'll come back when you let them cool off, and you're now forced to slow down the way you should have from the beginning, with the engine/gears.

It happened to me once in an old motorhome of mine; lesson learned. It happened to a friend of mine later on a dirt road and he was freaking out. I mean obviously it's not good, but often people assume their brakes are gone, for good. Once he understood what was going on he felt better and learned a lesson.

I use my gears on steep hills (lots of them out here), but also get a good confident feeling when I tap the brakes and can feel that both my brakes and the trailer brakes are working and can slow me down pretty easily. Just don't ride them.

These are more important life lessons that don't get taught like they should.

What to do with an out of control vehicle, etc. It's not clear if we'll ever know for sure, but during the time when Toyota was having an issue with accelerators getting stuck, and some people died, it's unclear whether it was a computer issue or just the floor mat getting stuck on the gas pedal. But, as crappy as it is to say, especially for the people who were on the phone with 911 while their vehicle was flying down the road, unable to stop, and they crashed and died...they very very likely never hit the brakes. In a battle between the brakes and the engine, the brakes win. Unless you've been riding them and they're overheated. But if you floor the gas and get up to 70mph, then slam the brakes, keeping your foot on the gas, too, the vehicle will stop.

Anyway knowing what to do with a stuck accelerator or if you lose the brakes is obviously important. Something to go through in your head before you find yourself in that situation.

[Byron Kinnaman]

I think this all depends on what you mean by "steep downhill" 14 miles of 6 or 7% grade or 100yards of 14% grade or something else.


A number o years ago while traveling in Maine I saw a sign that said trucks use lower gear for a stretch of pavement that went down at around a 10% grade for about 100 yards. Coming down off the Siskiyou Summit going into CA the grade was around 6 to 7% for several miles.


The longer and steeper grades (longer 10% or less) require a different strategy that the less steep grades and shorter.

[cvanzan]

I totally agree that using engine compression to help maintain speed on long, steep descents is the best method. This was easier with large cubic inch v8s and v10s. However, nowadays with low cubic inch/turbocharged engines putting out equivalent horsepower and torque it's not so simple. Nowhere near the compression. I've heard complaints of overheated transmissions using compression braking with the Ford 3.5L ecoboost on long descents.

With my Transit (3.5L ecoboost) I use a combination of compression and regular braking. I'll use a gear that keeps the van/trailer from accelerating more than 10 mph every 10 seconds or thereabouts, then use the brakes to slow back down to my base speed. Luckily the Transit is capable of handling significantly more than the weight of our Escape 21, so my base speed is close to the posted speed limit and I'm not irritating any traffic behind me. I drive over each of the Cascade Mountain passes several times/year and this system works well for me.
Charlie

[Jon Vermilye]

Originally Posted by Byron Kinnaman

I think this all depends on what you mean by "steep downhill" 14 miles of 6 or 7% grade or 100yards of 14% grade or something else.


A number o years ago while traveling in Maine I saw a sign that said trucks use lower gear for a stretch of pavement that went down at around a 10% grade for about 100 yards. Coming down off the Siskiyou Summit going into CA the grade was around 6 to 7% for several miles.


The longer and steeper grades (longer 10% or less) require a different strategy that the less steep grades and shorter.

If you want to test your ideas on strategies for steep hills, drive from Ricketts
Glen State Park in PA on PA 487 to Red Rock. A 2 mile 18% grade with a stop sign at the bottom.

It still is my favorite state park - 21 waterfalls along 2 streams.

[Byron Kinnaman]

Originally Posted by Jon Vermilye

If you want to test your ideas on strategies for steep hills, drive from Ricketts
Glen State Park in PA on PA 487 to Red Rock. A 2 mile 18% grade with a stop sign at the bottom.

It still is my favorite state park - 21 waterfalls along 2 streams.

I've never seen anyplace in PA with steep hills or high hills. If want steep and high you'll have to to Oregon, Washington, Montana, Colorado, Arizona. The test slope that has been used by automobile manufactures if outside of Bull Head City AZ heading for Kingman, AZ.

[Jon Vermilye]

Originally Posted by Byron Kinnaman

I've never seen anyplace in PA with steep hills or high hills. If want steep and high you'll have to to Oregon, Washington, Montana, Colorado, Arizona. The test slope that has been used by automobile manufactures if outside of Bull Head City AZ heading for Kingman, AZ.

I've spent quite a bit of time in all those states, and other than some off roading, that section of PA 487 is the steepest long stretch of paved state road I've driven, although the Teton Pass Highway (WY 22) & MT 49 north of 2 Medicine Campground are both "interesting" drives, as is the Moki Dugway (UT 261) although technically, the dugway isn't paved except for the switchbacks.

[alan H]

Another one to avoid ( if possible)
Donner pass going toward Sacramento ca

[floyd]

Originally Posted by Byron Kinnaman

I've never seen anyplace in PA with steep hills or high hills. If want steep and high you'll have to to Oregon, Washington, Montana, Colorado, Arizona. The test slope that has been used by automobile manufactures if outside of Bull Head City AZ heading for Kingman, AZ.

I've been all over the U.S. and I find more and steeper grades in the east than in the west. At least on highways. The reason is that the highways are much older in the east and had different grade standards when they were built than many modern highways in the west.

Now I agree that the difference may narrow as you migrate toward the backroads, but don't be fooled into thinking that the Appalachians are a lot less challenging than the Rockies just because the Rockies are taller.


Fact is, i find that some of the most worrisome roads are in North East Iowa believe it or not. Hundreds of STEEP short stretches of a mile or less one after another in close proximity. Worse than a long grade on equipment and on the driver when towing.

A stone riot in a good sports car though!

[floyd]

Originally Posted by alan H

Another one to avoid ( if possible)
Donner pass going toward Sacramento ca

Don't stop at the roadside restaurants either!

[Jon in AZ]

Originally Posted by Byron Kinnaman

I've never seen anyplace in PA with steep hills or high hills. If want steep and high you'll have to to Oregon, Washington, Montana, Colorado, Arizona. The test slope that has been used by automobile manufactures if outside of Bull Head City AZ heading for Kingman, AZ.

Yes the mountains in the West are higher in elevation, but the roads are generally far better engineered. I grew up in the East, and in the old back roads of the Appalachians you will indeed encounter steep grades, off-camber turns, narrow roadways with no shoulders, and other challenges that require careful descent control when towing.

EDIT... and I see Floyd has said much the same thing.

[Raspy]

Here's my favorite grade, the Sonora Pass on Hwy 108 in CA. 9,600 ft and as much as 26% grade. Especially interesting with the serious drop-offs that wait for those that don't make the curves along the narrow road.

Tractor trailer rigs commonly get stuck on this road, in spite of being advised not to take it, because they don't have enough traction to pull the load up the grade and have to be "rescued" after getting stuck on dry pavement. It's very entertaining to watch the proceedings and join the conversations that happen while waiting behind the blockages. It's deer country too, and the cops become mildly irritated after hitting deer while on their way to the location, at 1AM, for the umpteenth time. In that situation, they definitely find ticketable infractions. I call that particular spot "The Incident Zone".

While true that you should never ride the brakes to maintain a given speed, you absolutely must have trailer brakes that can be applied when needed to either get rid of excess speed or to stop an uncontrolled sway. Sway is more likely on a downgrade where the tow is pushing back against the trailer, and trailer brakes are the remedy.

[TZBrown]

Originally Posted by bobblangley

That's what I've read and been told. In fact, the local RV mechanic has told me to NEVER use OD when towing. That said, it's very tempting since I am towing a 3000# trailer with a 2002 Chevy diesel pickup that seems to be loafing along even with the trailer behind it.

Any comments/thoughts about this will be appreciated. Thanks to all.

With a Duramax the sweet spot is 1800 rpm for torque. if you are above that go up a gear, or use OD. With a 3K load you won't even drop out of OD unless the grade is over 7%.

I was involved in the development of those and the software. In the 2002 keep the transfer case oil changed, (use synthetic) as there was an issue with the drive chain wearing and contacting the case side, eventually a wearthrough would occur. JB weld was the field fix. I ran 200K on mine and had no issues at all.

[Kai in Seattle]

Floyd & alan H: Avoid Donner pass & restaurants for, gosh, so many reasons! Be sure your horses & oxen have snow treads, and always carry extra emergency rations.


Too soon?


"K"

[Kai in Seattle]

Use brakes to slow car before the grade, then downshift, touch brakes as needed...and maybe even put on your 4-way flashers. Possibly go a little slower than you could just to be sure.


Paul (with "K"

[Joe Romas]

Put your trailer information in your profile!

[RockyBob]

Oh the magic of overdrive! It's just another gear. There was a time, when a standard 3-speed manual was about all there was, that manufacturers would slap on an overdrive module (for extra money) that changed the gear ratio somewhat for extra economy. Then came four speed trannys and I guess those probably got OD options also. But now with 6, 7 and 8 speed transmissions pretty much the standard I suspect OD is just a top gear; presumably any gear that will be used for long periods of time ought to be designed to involve minimum number of gears and shafts, but they are all just different gear ratios.

Which gear to use when pulling? How about the gear ratio that allows the engine to spin at its sweet spot. If pulling a trailer means you don't have enough power to go as fast, then a lower gear will allow the engine to operate in its sweet spot. If, on the other hand, your power is plentiful for normal speeds, why would you want to use a lower gear and spin your engine faster than optimum?

[BushWacker]

To put it simply never "ride" the brakes, they will heat up and fail. If the gear you are in requires you to ride the brakes than shift to a lower gear.

[Rzrbrn]

Raspy, your pic of the Sonora Pass road sign says no vehicles over 25'. Does that mean combined vehicle length or just the length of the TV. My Tundra is about 20', say about 5' for the hitch, another 28' for the trailer for a total of say 53'. Would this combination be too long? Can I make it?

[Raspy]

Originally Posted by Rzrbrn

Raspy, your pic of the Sonora Pass road sign says no vehicles over 25'. Does that mean combined vehicle length or just the length of the TV. My Tundra is about 20', say about 5' for the hitch, another 28' for the trailer for a total of say 53'. Would this combination be too long? Can I make it?

Henry, I'm not sure what they mean by that 25' number. But you will certainly be fine. It's the big heavy semi-trucks that cannot make it. I've towed many times over that pass with my Ram and utility trailers, travel trailers, my tractor, a couple of cords of wood in a dump trailer and flat towed my Samurai. All longer rigs than 25'. You need sufficient power and gearing to pull the grade and sufficient brakes to hold back. Up or down, speed is not an issue as there are very few cars on that road. But I highly recommend it, as it is one beautiful drive, even after the recent fires. July is the best of all with afternoon thundershowers. Spectacular. Enjoy the trip!

A diesel with engine brake is the absolute best situation and I can come down without even touching the brakes. I've also, as a test, held the whole rig back with just the trailer brakes in order to get a feel for just how much they will do. It doesn't take long for them to fade. At least with Sonora, it's not one long high speed grade, but a series of ups and downs that give the brakes plenty of chances to cool. And there are beautiful places to stop if you wish.

My father had a '55 Dodge when I was kid that would not make it over Sonora Pass pulling our camp trailer with a burnt valve. That car had very poor brakes too. Once, coming down another grade from Cerro Gordo, out near Death Valley, and constantly having to stop and let the brakes cool, he decided to put it in reverse and use the throttle to hold it back. That worked fine, and got us safely down and home, but toasted the tranny. Cars, transmissions and brakes have come a very long way since those days.

My neighbor went down the Tejon Pass with a large Montana fifth wheel behind his 3/4 ton Silverado (no engine brake). It got away from him. He was panicked and standing on the brake pedal as the brakes faded to nothing and ruined the rotors in the process. He didn't crash it, but it definitely got his attention and he couldn't stop until the road leveled out. He replaced the rotors with the best aftermarket ones he could find, and ceramic pads, to fix a known weakness with those trucks.

[Rzrbrn]

Thank you Raspy. We really enjoy poking around the North East and also the Sierra Nevada mountains. Not sure where we will wind up but your Sonora Pass is pulling me...

This season will be the first pulling my BF 25.The 5.7L Tundra has plenty of HP for going up, just concerned abt going down. No real problems pulling a Casita, which is about 3K lighter in weight and single axle. But even with the Casita there are places we have been that required braking while in second gear. First gear would hold it but VERY slow, so I have only used first gear 2, maybe 3 times in 50K miles of pulling the Casita.

We have a couple of interesting roads in the Appalachian Mt range, one being Tail of the Dragon in NC. It was quite interesting to drive pulling the Casita. 318 switchbacks in 11 miles, total length is 14 miles. Up to 12% elevation change but no where is there a 26% grade. It is paved. No place to pull over, no place to turn around. 37 traffic deaths from 2000 to 2017.