How to manage brake systems on long downhills.
Braking for a long descent is primarily a speed chosen to keep the transmission out of overdrive (there may be two, even three of these gears today), AND a speed target which is easy to re-acquire after exceeding it. Usually the gear below Direct is the first one to choose barring further experience.
The gear chosen should be long enough to provide sufficient rpm to do the following (as there should be no gear changes until at the bottom):
Say one is using 35-mph as target. Once nearing forty, one uses the brakes of the combined vehicle to bring speed back down to 30-mph. And then allowing the brakes to cool as the rig continues the descent. Preferably the rise in speed isn't rapid. If it is, slow to a lower speed and lower gear. Do this while the brakes are fresh.
Not all grades are the same. One may be warned a 7% downgrade is ahead, but in fact only a stretch of it is that steep. So, don't go thinking that the next 7-percenter miles down the road is as easy. And if one hits that sharp decline with hot brakes, there may not be enough left to hold her back. (Last I heard the state will send you a bill for about $20,000 for a runaway ramp restoration). You young pups ain't had much fun without experiencing loss of brakes in the bias ply tires + drum brakes all around good old days.
What residual brakes remained depended on a slow descent. One has to get off the road, right then.
There's no substitute for best brake performance (lightest TV with big disc brakes plus discs on trailer; hint, it ain't a one ton).
Someone else brought up curves. Yes, the trailer is going to push the RV to the outside. I've been pushed completely off the road in an 84k oil field semi-truck by a downhill short sharp turn. In the flatlands of South Texas. A minor rain had changed yesterday's easy drive into an embarrassing slide today when the clay surface was wet. Sure, I was slow . . . but not near slow enough as I thought 8-mph was good. Engaged the second drive axle and then locked the differentials to crawl out. (I was later told at least 20 other trucks slid off that morning).
As to big trucks: the (really) old road down Berthoud Pass was a truck graveyard. They'd bring up the bodies. Usually.
Also mentioned above was making the ascent at high speed. Bad idea. There's always someone else having to slow. Running up behind them or next to them isn't wise. Lack of space. In the same way, an sustained engine load above 75-80% just burns fuel and heats things up for no good return. There'll be plenty of heat to shed on the way down in any event. Speed up the hill isn't any more relevant to flat land travel speed than speed down the hill. Break the hypnosis. Speed limit signs have no meaning in themselves.
Proper gear choice. Short use of combined brakes to reacquire target speed. Plenty of brake remaining to keep distance from others AND to be able to slam trailer brakes AND accelerate TV simultaneously to correct trailer sway.
There's no passage or vehicle more vulnerable to a loss of control accident than a rig like ours on a mountain descent. Hitch in compression is Russian Roulette.
Now let's add some wind gusts. (Their source won't matter).
1990 35' Silver Streak Sterling
; 9k GVWR.
2004 DODGE Cummins 305/555; 6-manual; 9k GVWR.
Hensley Arrow. 10-cpm solo, 18-cpm towing
Sold: Silver Streak Model 3411