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Old 06-04-2016, 05:44 AM   #57
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I can speak from experience working on school buses for years that "stab" does have merits. when you apply the brakes with moderate/ heavy pressure you are actually scraping a thin layer of the friction material off the pad/ shoe which provides a new layer of material the next time you use the brakes. If you "ride" the brakes the surface of the pad/shoe becomes glazed and ineffective. Also when "stab" braking as the friction material is wore away heat can go with it helping preserve the "goody" in the material that is left, when using constant braking the whole pad/ shoe becomes heat soaked and ineffective.

I have seen drivers ruin new brakes in 5000 miles from constant use. There was still 18/32 of friction material left on the shoe but it had no goodness left in it. We test our brakes monthly with a vericom meter and it becomes obvious if someone has ridden the brakes.

Steve
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Old 06-04-2016, 09:49 AM   #58
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Ok, but the OP is not driving a heavy duty class 6, 7, or 8 vehicle with air brakes. Some of the truth from the experience and research for these very large commercial vehicles may transfer over to the RV world, but the RP is driving "a Ram 1500 pulling a 29' Salem Cruise Lite 261BHXL".

The first article is referring specifically to air brake systems and how the systems are spec'd and adjusted. It says
Quote:
The amount of heat energy produced is dependent upon the weight of the truck and the amount of slowing desired. Assuming these two factors remain constant, the manner in which the brakes are applied, hard for a short time or lightly for a long time, will not change the amount of heat energy and heat produced by the brakes. This heat energy will be distributed among all the brakes that are working. Again, assuming all other factors constant, the more brakes the system has working the cooler each brake will be. (emphasis added)
Since the OP is pulling a fairly good sized trailer with a 1500 truck, it might be the best advice to drive down a hill in a gear where no brake use is needed, or only very rare occasional use of braking in order to prevent the engine from going over the engine redline.

The second article echoed some of the info from the second article, and also says
Quote:
"What you want is all the brakes working some of the time, not some of the brakes working all the time. The application pressure must be high enough to ensure that all brake chambers apply and that all linings make solid contact with the drums"
but again is geared (pun intended?) towards air brake systems, which the OP doesn't have.

It seems to me that what is much more important than which braking technique is argued over is to stress that the brakes are all being applied equally. In the pickup truck tow vehicle, this is easy: the brakes are more than likely hydraulic disk brakes, and unless there is a fault with the mechanics of that brake system, will always apply with equal force.

Electric trailer brakes, however, should not be easily trusted. The owner should either learn to inspect and adjust the particular system they have, or make sure that they get the electric braking system inspected and adjusted before each camping season. The benefit of doing this will be that any potential braking problems might be discovered before it becomes a safety issue.

Even after inspected and adjusted, I believe it is best to descend in a gear that will provide enough engine braking to not use the brakes at all. This seems like the very best way to have all of the braking ability of the truck and trailer available for emergency braking should the need arise. If this is not possible, then descend slowly enough to only use the brakes as little as possible. Every grade will be different, and as it was already mentioned, it is better to start out in a lower gear than need, than to find that you've gotten your brakes too hot and can't stop if you need to.

Thanks for the info.
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Old 06-04-2016, 03:14 PM   #59
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Water cooled brakes work
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Old 06-04-2016, 07:03 PM   #60
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1bigmess, while I dont agree with the first quote I can't argue with anything you stated. You have some valid points.
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Old 06-04-2016, 08:06 PM   #61
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A point the articles don't fully address is the relationship between deceleration due to braking versus other factors. Does pressing the service brake lessen or eliminate the stopping force gained from the transmission or exhaust brake? The articles suggest that applying 10psi all the way down, or 20psi with a 50% duty cycle, or 40psi for 25% would all generate the same amount of heat. If application of the service brakes reduces or eliminates the stopping effectiveness of the other factors, then would it imply that the brakes effectively do more work over the entire descent at 100% duty cycle than at 25% where the other factors are allowed to make a 75% contribution?
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Old 06-04-2016, 08:24 PM   #62
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A point the articles don't fully address is the relationship between deceleration due to braking versus other factors. Does pressing the service brake lessen or eliminate the stopping force gained from the transmission or exhaust brake? The articles suggest that applying 10psi all the way down, or 20psi with a 50% duty cycle, or 40psi for 25% would all generate the same amount of heat. If application of the service brakes reduces or eliminates the stopping effectiveness of the other factors, then would it imply that the brakes effectively do more work over the entire descent at 100% duty cycle than at 25% where the other factors are allowed to make a 75% contribution?
Uhhhh, I would use the other devices ( engine compression, Jake brake, exhaust brake, etc.) to do most or all of the work to keep the vehicle at a safe speed and the brakes to slow further if needed, or to stop. It just seems easier to think of it like that to me.

Stay safe.

Steve
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Old 06-04-2016, 09:09 PM   #63
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.....
Is a 6-10% grade different out there? US33 has 9% grades for 5 miles on either side of a pass in WV and I'm trying to figure out how that is different than a 9% grade for five miles on either side of a pass "out west". Sure there are places like Teton Pass that have 6-10% grades for a similar distance on either side but we're splitting hairs. The only difference is elevation at the summit.
.........
Yes they are different sometimes VERY different. I'll explain

THe main difference is the altitude many of the Steep grades out west start off at a higher altitude than what the tallest summit (Spruce Knob 4863 ft) in West Virginia.
(The lowest point in colorado is Arikaree River at the Kansas border
3,317 ft )

Monarch pass in Colorado goes up to 11,312 feet. 6% grade 9 miles long to sargents Co (8478FT) to the west. The 6% to the east for 10 miles.

Less air for you engine to make power with. (gas Non-turbo loose 3 % for every 1000 FT)
AND less air to cool your engine (going up)
AND less air to cool the brakes. (going down)
And less air for your engine to use for compression braking. (going down)

the other differences is that on some grades there are sharp turns. This is Not on the interstates but on some other roads you will see it.

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Old 06-04-2016, 10:21 PM   #64
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Originally Posted by Mekanic View Post
Less air for you engine to make power with. (gas Non-turbo loose 3 % for every 1000 FT)
AND less air to cool your engine (going up)
AND less air to cool the brakes. (going down)
And less air for your engine to use for compression braking. (going down)
I think you are confusing "air" and "oxygen".
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Old 06-04-2016, 11:14 PM   #65
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"Do you know anything about the drive from Albuquerque ->Farmington ->Cortez ->Monument Valley ->Page ->Grand Canyon -> Phoenix -> Tucson ->Carlsbad?

All of these routes have some longer grades, but not too steep, but if going from Flagstaff to Phoenix, there is a very long uphill/downhill section that will strain most any vehicle, especially in 100d+ temps. Many semis can't do more than 20 up and not much better down.
550 Alb-Fmtn is mostly 4-lane now, and much better condition than several years back. Cuba is about 1/2 way, plan on gas/tacos/ice cream there, about the only decent stop on the road. This is Indian Country big time...
You are going to have to get used to 4500rpm noise a lot...
Leaving tomorrow to head from Ft Worth to Provo, UT--will be going over a lot of those roads, towing 17.k with a 450. There are stretches that will let me know that I have a load behind me.
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Old 06-04-2016, 11:29 PM   #66
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Good point about the temperatures. There is a climb in California that I can normally do in one shot. At 105F ambient temperature, I had to stop to cool down twice. Going down the other side, I passed a fifth wheel heading up with the pickup fully engulfed in flames. Definitely respect what your temperature gauges are telling you and remember to turn off the AC.
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Old 06-04-2016, 11:36 PM   #67
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"Do you know anything about the drive from Albuquerque ->Farmington ->Cortez ->Monument Valley ->Page ->Grand Canyon -> Phoenix -> Tucson ->Carlsbad?

All of these routes have some longer grades, but not too steep, but if going from Flagstaff to Phoenix, there is a very long uphill/downhill section that will strain most any vehicle, especially in 100d+ temps. Many semis can't do more than 20 up and not much better down.
550 Alb-Fmtn is mostly 4-lane now, and much better condition than several years back. Cuba is about 1/2 way, plan on gas/tacos/ice cream there, about the only decent stop on the road. This is Indian Country big time...
You are going to have to get used to 4500rpm noise a lot...
Leaving tomorrow to head from Ft Worth to Provo, UT--will be going over a lot of those roads, towing 17.k with a 450. There are stretches that will let me know that I have a load behind me.
Joe
Thank you for that VERY helpful info. We will be leaving Flagstaff early and have to be in Phoenix by 1pm. Hopefully that's doable, even with the terrain. We were planning on doing the Oak Creek Canyon scenic drive (route 89a) between Flagstaff and Sedona on the way, but I'm thinking that might not be possible while pulling the camper, given that it ascends 4500 feet to the top of the Magollon Rim. The drive is only 14 miles long, but still...
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Old 06-05-2016, 06:55 AM   #68
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When going down hill, start slow, stay slow, use your tow haul mode relax and don't worry about the cars behind you they're going to complain at any speed. The more speed you gain the harder it is to scrub.
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Old 06-05-2016, 07:57 AM   #69
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Yes they are different sometimes VERY different. I'll explain

THe main difference is the altitude many of the Steep grades out west start off at a higher altitude than what the tallest summit (Spruce Knob 4863 ft) in West Virginia.
(The lowest point in colorado is Arikaree River at the Kansas border
3,317 ft )

Monarch pass in Colorado goes up to 11,312 feet. 6% grade 9 miles long to sargents Co (8478FT) to the west. The 6% to the east for 10 miles.

Less air for you engine to make power with. (gas Non-turbo loose 3 % for every 1000 FT)
AND less air to cool your engine (going up)
AND less air to cool the brakes. (going down)
And less air for your engine to use for compression braking. (going down)

the other differences is that on some grades there are sharp turns. This is Not on the interstates but on some other roads you will see it.


The amount of air is the same at 12,000' as it is at 3,000 but it's components are different. Oxygen is the main one which is why power is reduced. You still have the same amount of air in it's different components moving over your engine and brakes. Unless you are actively running your engine to slow down vs. passively letting it's resistance do that, the reduction in power really shouldn't matter.

The air cools 3.5-5.5 for 1,000' of elevation so if anything, it should be cooler at 12,000' than it is at a 3,000' summit which means there would be more cool air to cool your engine & brakes.

As for the notion that none of the steep grades in the east have sharp turns is not accurate. What do you think they do with a 10% grade for five miles - just go straight down? No, they curve just like they do out west.

The elevations may be different, but a mountain is a mountain. Our mountains have the same vertical rise, tree lines (except ours are lower), weather, etc. The Rockies are just bigger and I'm not going to deny that there are isolated places that might have longer grades but you still need to know how to drive down those grades or just pass it off because you are not "out west". That's how people die every year.
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Old 06-05-2016, 09:38 AM   #70
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Quote:
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The amount of air is the same at 12,000' as it is at 3,000 but it's components are different. Oxygen is the main one which is why power is reduced. You still have the same amount of air in it's different components moving over your engine and brakes.

Take a pneumatic piston, open it's control ports (valves) to freely allow air in or out., and move the rod to a position where there is 2 inches of air in the chamber. Seal the port. Think of a hypodermic syringe if you are not familiar with pneumatic components. The pressure in the cylinder now matches the ambient pressure in the room, lets say 14 psi. Mechanically push the rod in so that the chamber size is reduced from 2 inches to 1 inch. The same number of air molecules are in the chamber, but now they are contained in half the volume. The pressure is doubled to 28 psi.
Now mechanically pull the rod so that the chamber is 4 inches long. Same number of air molecules, same ratio of nitrogen to oxygen to carbon dioxide etc., but in twice the volume. The pressure is now 7 psi. There is now less air (half as many molecules) per cubic inch in the chamber.
As stated, with the exception of a turbo boosting intake air pressure, there is less air per cubic inch at altitude than at sea level. Absolute air pressure at 4000 feet is about 12.7 psia versus 14.7 at sea level.
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