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Old 04-23-2018, 08:58 PM   #1
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Driving down the mountain

For those who have traveled pulling their 5th wheels down hills, I have a question. Driving west on I-80 from Park City Utah to Salt Lake City, I know that the interstate has a very steep grade. What gear do most use while coming down the mountain? And, what is a safe speed to maintain in order for the 18 wheelers to stay off your butt?
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Old 04-23-2018, 09:21 PM   #2
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Generally, go down the grade in the same gear you used to climb it.
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Old 04-23-2018, 09:28 PM   #3
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I just drove down a mountain grade this weekend, 2nd gear and just cruise, hardly used the brakes at all...don't be intimidated, very doable
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Old 04-23-2018, 09:55 PM   #4
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Driving down Parley's grade (I-80 W to SLC) keep around 45 to 50 MPH with RPMs up about 75% of red line. Do not worry about the semis, some loaded ones will be driving at 35 to 40 and some empty ones at 65. Drive your speed and stay in right lane except to pass. The steepest part is the first couple of miles off of the summit, then not so bad, then further on a bit steeper again with lots of curves.
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Old 04-23-2018, 09:58 PM   #5
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Driving down Parley's grade (I-80 W to SLC) keep around 45 to 50 MPH with RPMs up about 75% of red line. Do not worry about the semis, some loaded ones will be driving at 35 to 40 and some empty ones at 65. Drive your speed and stay in right lane except to pass. The steepest part is the first couple of miles off of the summit, then not so bad, then further on a bit steeper again with lots of curves.
Nearly the same for going east off Parley....If you have to "spike" your brakes more than twice in a mile of travel..slow down/gear down....
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Old 04-23-2018, 10:04 PM   #6
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Do you have a relatively modern diesel? If so, they will do 90%+ of the work for you.

Exhaust Brake ON
Tow Haul ON
Jab brakes upon start of decent to desired speed ( i typically do about 5 over...)
Coast and enjoy the ride. the Truck will close the vanes on the Turbo and manage the gearing appropriately.

Older Diesel or a Gasser?

or if the exhaust brake can't handle the grade, which is not very often on my Ford 6.7L....Keep the Revs up - use the same gear you used pulling up the hill to go down it. If this isnt keeping you at the desired speed... HARD BUT CONTROLLED jab at brakes and drop 5mph under desired speed. Let off brakes entirely and let them cool as you speed up. Rinse repeat. This will have you surging between 5 under and 5 over the speed limit, but will keep your service brakes cool and available.

Keep off the brakes except for those short and intense braking periods to bring your speed down - they need to cool.

EDIT: We did Utah and Park city last year and it was spectacular. Enjoy .
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Old 04-23-2018, 10:57 PM   #7
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... If this isnt keeping you at the desired speed... HARD BUT CONTROLLED jab at brakes and drop 5mph under desired speed. Let off brakes entirely and let them cool as you speed up. Rinse repeat. This will have you surging between 5 under and 5 over the speed limit, but will keep your service brakes cool and available.

Keep off the brakes except for those short and intense braking periods to bring your speed down - they need to cool...
Of course this periodic braking technique has been thought as needed for long downhill grades with a load for a long time. It may still be best for trucks with air brakes and large drums (not sure), but for most late model light trucks and motorhomes there is really no real benefit. Vented disk brakes remove any advantage. Better just to apply constant brake pressure and maintain constant speed.

The braking energy is the same in either case, and the energy is converted to heat via brake friction. Pressing hard generates heat at a higher rate heating brakes faster, balancing the "cooling" effect of releasing the brakes.

I know the "brakes on / brakes off" method has been preached for decades, but does not mean that it is really the best way to drive.
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Old 04-23-2018, 11:02 PM   #8
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Of course this periodic braking technique has been thought as needed for long downhill grades with a load for a long time. It may still be best for trucks with air brakes and large drums (not sure), but for most late model light trucks and motorhomes there is really no real benefit. Vented disk brakes remove any advantage. Better just to apply constant brake pressure and maintain constant speed.
Remember, the trailer almost always has DRUM BRAKES! I faded out my brakes doing just what you said coming down Eisenhower Pass on the way home to Denver, with my last Diesel (no exhaust brake).

And the math doesn't actually work out, because even a light drag on the pads with basically no work done will still result in quite a bit of heat transfer from the disks to the shoe material - again you aren't actually getting any additional braking as you ride the brakes gently, but you are nicely facilitating heat transfer from your large vented steel disk to the small compact, and not vented brake pad - as opposed to when you are off the brake entirely and the pads are riding on a air cushion largely preventing heat transfer from the rotor to pad and letting both cool.

I'll stick with the pulse .
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Old 04-23-2018, 11:12 PM   #9
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Of course this periodic braking technique has been thought as needed for long downhill grades with a load for a long time. It may still be best for trucks with air brakes and large drums (not sure), but for most late model light trucks and motorhomes there is really no real benefit. Vented disk brakes remove any advantage. Better just to apply constant brake pressure and maintain constant speed.

The braking energy is the same in either case, and the energy is converted to heat via brake friction. Pressing hard generates heat at a higher rate heating brakes faster, balancing the "cooling" effect of releasing the brakes.

I know the "brakes on / brakes off" method has been preached for decades, but does not mean that it is really the best way to drive.
With either hydraulic or air brakes......
You can fry a set of disc brakes just as easily as drum brakes..Just takes a few minutes longer...
I will stand on nearly 50 years and a goodly number of miles under my butt with both drum and in later years disc brakes.. when recommending one use the "gear down" & "spike & cool" method, with disc or drum brakes..
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Old 04-23-2018, 11:15 PM   #10
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Even with vented disc brakes you don't want to keep constant pressure on your brakes anytime. ..get the fluid boiling and yer in trouble. ..just read a post here last week or so about someone who boiled their brakes and fluid
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Old 04-23-2018, 11:26 PM   #11
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Driving down the mountain

A lot of years driving big rigs up and down some big hills. Both drum and disc brakes stab braking or however you think or call it is the way down the hill. Basic driver 101 even today with disc brakes
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Old 04-23-2018, 11:30 PM   #12
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Regarding brake technique: Well, just read the attached research on this. The results show that average brake temperatures are same in with either "pulsing" or "constant drag", but that the higher brake pressure seen in the pulsing method results in more uniform heating among all the brakes on the vehicle, thereby reducing the event of one brake getting overheated.

So pulse away - good thing.

Article:
https://deepblue.lib.umich.edu/bitst...pdf?sequence=2
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Old 04-24-2018, 01:02 AM   #13
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Going down down Parley's canyon I'd start at about 45 MPH.

I go up and down mountains by RPM and never exceed 4,000 rpm on my 8.1 gas engine.

I shift to lower gears and when I get to 4,000 rpms I mash on the brakes for no more than 5 seconds and my rpms will drop to about 3,000. I then let it creep back to 4,000 rpms.

Do not worry about the traffic behind you, they can pass you in the other lane.

Do not ride your brakes!!
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Old 04-24-2018, 03:20 AM   #14
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Quote:
Originally Posted by YooperVer View Post
Of course this periodic braking technique has been thought as needed for long downhill grades with a load for a long time. It may still be best for trucks with air brakes and large drums (not sure), but for most late model light trucks and motorhomes there is really no real benefit. Vented disk brakes remove any advantage. Better just to apply constant brake pressure and maintain constant speed.

The braking energy is the same in either case, and the energy is converted to heat via brake friction. Pressing hard generates heat at a higher rate heating brakes faster, balancing the "cooling" effect of releasing the brakes.

I know the "brakes on / brakes off" method has been preached for decades, but does not mean that it is really the best way to drive.
Have to disagree. Staying on the brakes in steep grades in motorhomes I've had with disc brakes will bring brake fade and burning brake smell... The tried and true method of using brakes fairly hard to scrub about 10 mph off your speed, then getting off until it has regained speed, stands... IMHO.
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