Going downhills advice needed.

I guess I don't get your reply?? My original question was the 300 600 shifting scenario that turned into a flasher forum. LOL. I am not sure about yer bad weather comments and learning them in good weather. Nobody is asking a question of " being out in it". But like most posts or threads that start out with a valid question they seem to get turned into something different. ANYWAYS. Thanks fer yer advice

 

wait, is it illegal to have a bicycle on the back of my tractor? what about in canada?

FYI, i will never go to california again!

 

That's the way you do it. If you don't know the grade JUST SLOW DOWN. I too have never smoked the brakes and I've hauled alot of overloads weighing in over 100,000lbs.

 

I think the big problem is when you are in an unfamilliar area, have a time deadline, & it seems like every truck on the road is passing you. It is human to feel the push & want to go faster.

 

You heard about the legend of Jesse James and John Henry just to mention some names.........................

yep, IIRC SD 40

just don't do it.

 

PLEASE don't do the 5mph +/- procedure it will kill you eventually.

Kinetic energy=1/2 * mass * velocity squared or (KE=1/2MV^2)

When you let the speed (velocity) increase a little you increase by a bunch the amount of energy your brakes must dissipate. Say you allow the speed to double, the heat or energy your brakes must handle goes up by 4 times.

Another way to say this is you generate far more brake heat getting rid of those extra 5 mph than you lose by letting the brakes 'rest' while your speed builds back up.

Light steady pressure at a slow enough speed is better. Both techniques will work well enough on some grades so the people with a strong preference, even for the more dangerous technique, will have episodes that seem to confirm their preference. But physics doesn't care about opinions and trucks operate according to physics.

 

tscottme,
Thanks for the info. Where does it come from ? Appreciate it............

 

jtrnr1951,

While I wholeheartedly agree with tscottme and others who advocate the steady pressure method (it was the way I was taught), here is a study that you might wish to peruse ...

The entire paper can be found at http://deepblue.lib.umich.edu/bitstream/2027.42/960/2/82902.0001.001.pdf​

A word of caution about the link. It is a 100 page pdf file. I wouldn't click on it unless you have a reasonable internet connection. I don't wish to have my legitimate ancestry called into question by someone with a marginal connection who clicks on this and then "hangs" for an extended period while all the data is loaded.​

 

tscottme, I get what you are saying, but the +/- 5mph doesn't double your speed. Common sense (and physics) tells me that putting a constant 10 psi versus pulsing 10 psi will generate more heat.

Of course, right now I'm only talking in theory. Being in Florida, I haven't driven on any grades. Once I get out there I'll see which I like the best. I'm betting on the third option: Jake brake.

 

I've heard people swear that constant pressure is best and I've heard the people swear the opposite.

Actually common sense tells me that constant pressure will generate less heat. Think of it this way, if you were to get up to speed going up a hill, ease off the throttle until you dropped 5 mph and repeated would you use more energy than if you kept a constant speed? Of course you would. The energy saved while 'coasting' doesn't make up for the energy used to get back up to speed. Going down hill the energy (heat) created while slowing will be greater than the energy (heat dissipated) saved while picking up speed.

The question is whether or not the heat that is dissipated from the inside of the drum while coasting makes up more than the difference.