braking on big mountains...

With the jake's on or off and at gross weight ?

 

No jakes, I just gear lower and approach it slower.

 

That is the 3/5 rule. Pick a speed 5 mph under the posted limit. Speed starts to climb = brake for 3 seconds. Repeat when needed. Being in the right gear is key. If you do this in top gear, I'll be seeing you on the escape ramp.

Stab braking is when you hit the brakes hard enough that the wheels start to lock up, then you ease off the brake pedal. Stab braking is what you would use when you need to come to a panic stop.

 

There is a mountain on a NW Georgia back road east of I 75, don't remember where I picked up. It caught me by surprise in a no jake truck with a full load of canned goods I believe, it was a full heavy load anyway. The classic nightmare scenario , enter a long unmarked % grade only a downhill sign, curve to end at a T stop at the bottom where I made a right somehow. At the bottom of course was a drop off you could not see bottom, you were dead if you went off it. I thought I was a dead man on a mountain once, and that was the day. Somehow my brakes did not fade, just a little smoke.

Never underestimate a new hill.

 

Kinetic energy = 1/2 x mass x velocity squared.

That means getting rid of 5 mph in speed after you have it puts more heat into the brakes than keeping the speed constant. Light and steady pressure is what I settled on after running a year of alternating between L&S and staying under the posted advisory speed but letting speed build and then slowing back below my reference speed.

Say the yellow advisory sign says 40 mph for a given weight. I might gear down and try 35 mph as a reference speed. When my speed built to 40 I'd apply very light braking to slow to 30, "rinse and repeat." With L&S pressure I'd gear properly and use the smallest amount of braking to keep my speed at 30-35.

Early in my career I traveled often enough up and down the Cajon pass between Victorville, CA and Ontario, CA on I-15 that I could carefully experiment. Never did I have a "jake brake". After much experimenting I settled on the Light & Steady pressure method. Then a few years ago I remembered the formula for kinetic energy. That's the energy your brakes must convert to heat to slow you down, not that physics should influence a truck driver to do the right thing.

If you do either method badly, usually going too fast for weight/grade and making harsh brake application a truck driver can screw up any method.

 

I-8 east of San Diego kicked my butt a couple of times. The first time, I wasn't very surprised I smoked the brakes and good. The second time I was surprised but only smoked them once closer to the bottom, instead of 2-3 times like the first trip. I hardly smoked the brakes on the third and never again. I-8 in that section between San Diego and El Centro winds around quite a bit as you come downhill. It seems like you are almost at the bottom and I mistakenly "let it go" only to quickly "learn" we still had a lot of hill left to descend.

 

Cajon Pass is a "HILL" !!?? That's new to me and I run it everyday. I thought the speed was 45 so you wouldn't blow by the coop's.

 

I live at the top of three mile grade along I-80 west of donner. I see many trucks daily with smokin brakes, once every couple weeks we get one that catches fire. A couple weeks back one burnt down right below my house. I wish every driver that drives that road would read this thread. When the last truck burned down, we were packing gettin ready to evacuate, was a bad experience. When the tires started blwing up it shook my entire house, felt like bombs going off.

 

That's the key phrase. Only a imbecile would attack a hill in top gear and anyone, no matter how you brake will end up on a ramp.

The thing about braking is to keep it to a minimum and let the gears and engine brake share the work. The faster you go, the harder everything has to work.

Brakes have to be adjusted properly or some are working harder than others. It doesn't matter how you do it, when you press that pedal, friction and brake fade starts. If you press constantly and lightly, I guarantee you even though you are maintaining a constant pedal pressure, your pedal travel is increasing compensating the fade.

They are making better linings today that withstand higher temperatures. But that drum will still expand with heat.

Most of these Interstate mountains are 7% grade and are really not that difficult. The longer or steeper the grade, the more chance of fade. Black Mountain and the one on I-26 outside Johnson City are more difficult than Monteagle, the Grapevine and Vale, IMO.

I checked the manual. You are correct on the term stab braking. I can swear when I went to school, the 3/5 rule as you call it, was called stab braking then. I started when ABS was being implemented, so I know the old ways too. I wish I had an old manual, lol. But even the manual says the 3/5 is the proper technique. This is suppose to come from engineers doing extensive testing. The manual is not going to tell you something wrong.

 

There is Snub braking,

and

There is Stab braking..........


The last I knew, Snub was the preferred method !!