Down hill jake braking, what speed and gear do you use?

It's alot easier to speed up than slow down.

 

The jakes were holding fine, they only can do so much. If you had to get on the brakes a lot, then you were going too fast for the weight on that steep of a grade. 40-45 mph is probably closer.
If you have to use more than 10 psi air brake pressure, you’re still going too fast. At 30 psi air brake applied pressure you can start to smoke the brakes.
Don’t worry about how fast everyone else is going, you don’t know how much weight they have or what their truck engine is capable of.

 

Back in the day the general rule was when going down a mountain start out in 1 gear lower,on the way down,than you used to climb up there.
Big hp is a lot better for mountains going up and back down.With a low rpm Detroit, if the speed limit said trucks 55,I would start out going down at 35 or 40,let it build up a little speed if everything is good.

 

I find my truck, heavy on long grades, that mt jake holds me best in the 30-35 MPH range.

Keeps me from hitting the brakes much. I know some later engines have more efficient jakes

 

Set a 10-15psi application on the trailer and make the shift. If you have a shift bar, if you’re connected to the transmission with wires I’d leave it where it was. If the computer ####s the shift up pulling on the wires harder won’t help, and the last thing you want is a truck out of gear on a grade.

 

Wow lm surprised to see 55mph down a 6% grade. I guess we are not talking weather this 6% grade is straightaway or if it has curves rated at 35mph or what. Ive never seen many mountain grades that are straightaway out west. I would be down at 30mph with Jake on medium.

 

I can drop off the west side of Lookout at 74k gross and not have to touch the brakes at 55mph in this new truck. On flat ground I’d be eating the windshield if I used the third stage.

To the OP…..if you’re used to newer engines you’ll have to dial it back a couple notches for the 12.7. The engine brake simply isn’t as strong.

 

Going down lookout i would always start at about 35mph at the top . but could start grabbing gears about halfway down. Im always slower than everybody else down the mountains

 

When we were 105k with a Cat you had to hold it back until the second runaway ramp. Lol

 

Agreed on 1 gear lower than you climbed it.

 

I commonly run those conditions. 75k to 79k gross weight and 6% for miles. I do it all the time. For me and my set up, I run such grades between 40 to 45 mph. My Jake will pretty much hold me at that speed, although I might need to pump on the brakes a bit here and there. I get up to 45 mph, I brake back down to 40 mph. But, if I have to do that braking maneuver too often, it means I need to run another 5mph slower. Also, I drive an automatic, so I don't think it's as complicated as running it on a manual. That said, I do choose the gear I'm running a downgrade in. I can manually up or down shift and if I'm not in the right gear, I'll adjust. Typically, such a grade I'll run in 9th. Some grades, such as the grapevine in Southern California, has a 35 mph speed limit, which means, I run between 32 and about 36 mph and usually have it in 8th.
It basically has to do with NOT overheating your brakes. Everytime you use your brakes, you heat them up. It creates alot less heat in your brakes to slow down 5 mph when you are going 45 mph than when you are going 55 mph. The basic reason you run downgrade slower. You have to keep those brakes functional and too much heat in the brakes render them useless. With gravity really trying to push you down a grade, it can be fatal. It is often stated, you can go down a grade too slow, but generally you'll only go down a grade too fast 1 time.
I do get passed by others alot and seldom need to pass another. Which means I'm usually the slowest going down a grade. Doesn't matter, it isn't a race. And, if you are lighter, which many are, you can safely go down a grade at a faster speed. So, I don't judge. But for me, I'm taking it slow and easy. I do it routinely and don't have any problems. But, I always respect any grade I encounter. There are ALOT of laws you can break, but the laws of basic physics are immutable. Fines can be fatal!! It's just the way the Universe works!!!!