proper way to decend grade

[Songman]

You see, that is the thing for me, zimtok. As a relatively new driver of buses, I am here to learn. Obviously there is more than one way to do anything.. Probably even more than one way to do it correctly. But never more than one way to do it best.

And I really am not trying to be an @$# here... But on the one hand, I have a degreed expert saying one thing, and then on the other, a guy is saying that all the testing is invalid and it has been proven scientifically. Now I know the expert has scientific testing, but I honestly want to see the other side scientific testing. This is a real search for knowledge. Not a prove someone right or wrong.

Also, there are two sides here saying the each way bleeds off heat better. They both can't be true.

Honestly, my gut tells me that fleet rigs probably have brakes tested more than a person's bus would... So again, even by what Jerry said, go with the one that works best in less than optimal conditions.

[tekebird]

Lets see some articles, test results etc for the Steady pressure.

I always try to have backup documentation when I pipe up in here and often post links to the same ( search tire ballancing)

I had loads of backup doc and the gentleman who said tire ballancing was poppy cock....could not come up with any

[Busted Knuckle]

Lets see some articles, test results etc for the Steady pressure.

I always try to have backup documentation when I pipe up in here and often post links to the same ( search tire ballancing)

I had loads of backup doc and the gentleman who said tire ballancing was poppy cock....could not come up with any

Yes Doug I have to agree you usually do have the documentation to back up what you say, and also usually provide links to it!  I have to agree that it sure makes it easier to follow your train of thought (even though I don't always agree 100%), I have to give credit where due! I on the other hand usually don't take time to research/provide links to documentation on what I say/post as I usually speak from the School Of Hard Knocks (experience) which I have graduated from! I may not know much, but I have survived 20+ yrs of over the road driving experiences and have been just about everywhere in the US that you can drive too! (with Alaska being the one exception)
That being said I'll politely back out of a subject which I am truly under qualified to comment on!
  BK 

[Songman]

BK, you're on the same side with that edukated feller this time.

[buswarrior]

I go away for a couple days and you guys.....

two parts to my post, some pi$$ing and a training example:

Pi$$ing:

One other poster mentioned the key factor:

What SPEED are we talking about?

No matter which Blessed House of the Mountain Descent you happen to be a member of...

The big issue when teaching either method is to keep the SPEED well under control, for many/most descents in the bus or a truck, meaning below the posted speed limits

Both Blessed Houses can agree to choose a lower gear which helps to maintain a certain lower SPEED

SPEED makes exponential heat, so the slower one goes, the less heat to be made in the brakes when controlling it. The faster one goes, great whallops of heat must be dealt with.

In litigious America.... if some government body advocated a certain driving technique which was flawed... and its use caused a death, or two.... You don't suppose that a court would have put a stop to this "snub braking" long ago, and awarded the plaintiff a huge sum?

As for balanced braking, unless you hook your brake lines up to gauges to check for plumbing functionality, and put the wheels on a brake dynometer to ensure mechanical functionaility, you have no way of knowing which end of your coach, or which side, or which ONE, is doing all your stopping.

I would bet that out of the membership of this board, there will be a couple of buses that do most of their stopping with the front brakes, the relay valve in the back having failed to apply the called for pressure to the brake chambers, or the foot valve failed to call. Yes the linkage moves, but how hard is it squeezing?

And then a whole bunch more of us have brake linings that were destroyed by the abuses of the previous owner, or ourselves, and they don't produce the proper friction when they are squeezed against the drums.

Way too much science and measurable facts are available, personal experience lacks control or measurement of the variables. And few, if any of us, are able to confirm that our ride is in tip top shape, gripping the road according to spec under all tires.

eh?

Training example:

MC8, 8V71 with HT740 auto tranny, 3.7 diff gear, NO Jake.

Downhill off Fancy Gap in Virginia, I77. some what? 5 miles of 5-6 % ?

Snub braking target is 45 mph.

3rd gear in auto tranny

used the brakes three times over that 5 miles to snub the speed down to 40 mph

At a higher target speed, or in a higher gear, the coach accelerates downhill faster after the brake application, requiring more frequent use of the brakes.

The trick is to keep lowering your target speed to a point, and a gear, where the coach only accelerates downhill lazily and requires little use of the brakes.

Best advice on here has been stated twice before, and paraphrased here:

You'll only go down too fast once.... take your time!

happy coaching!
buswarrior

[Jerry Liebler]

Buswarrior,
    VERY WELL SAID.  However we all should try to keep our equipment in the best shape possible.  Even with  'snub' braking those brake issues you've mentioned will cause a, possibly great, difference in temperature of different wheels.  Brake failures happen with 'snub' braking too.   It's still a good idea to every now and then descend a long grade using the  'ride the brakes' technique then stop at the bottom and check the relative temperatures with that handy infrared thermometer.  If only the front brakes are hot you'd best get that relay valve, or whatever the cause is, fixed. Likewise if the left is much hotter than the right on one axle you'd best find out why and fix it.  To be safest we all need to go slow enough, have properly maintained TESTED equipment and use the 'snub technique'.
Regards
Jerry 4107 1120

[maria-n-skip]

 I have been reading this thread with much interest. No matter how good of a PM or current maintenance ones
 has things can go south very quickly. BT more than once so I don't think I have anymore grace in this matter.

 So along the same vain IS there anytime dynamiting the brakes is a proper choice?

 Personally I have always looked for a soft bank.....not always available though!

 A runaway is probably the scariest thing I have ever been through, something I hope nobody here
 has to go through.......


  Skip

[gus]

Just because some guy with the degree in Automotive Technology says it is so doesn't make it so. One can study books and accident reports all day and know nothing about braking heavy vehicles. My ole Grandpappy always told me to watch out for any guy who calls himself an expert.

Where is the documentation that shows a direct comparison of the two types was made under actual condition-lab results don't prove a thing?

Constant braking has worked for me both with an 80,000 lb 18 wheeler and my 4104, never have I even had my brakes get so hot they smoked or smelled, so there has to be pretty strong proof to get me to change.

[TomC]

Chaz- I also have the V730 in my bus and use the shifter all the time.  First to down shift as soon as I can, makes for smoother down shifts than to wait for the transmission. 
I also downshift going down steep grades.  I've been in 1st going 20-30mph on twisty mountain roads (Kern River to Bakersfield).  You can use the lower 2 gears also, as long as you have a shift selector that says R-N-3-2-1.  If you just have a F-N-R, you won't be able to down shift.  A properly adjusted Allison will not allow the transmission to down shift until you're at the proper rpm-so you don't have to worry about over speeding the engine.  Good Luck, TomC

[Don4107]

Hey Jerry or anyone else that wants to prove their position,

How about a little test?  Make a run down a hill using constant pressure braking at say 40mph.  Then make the same run using snub braking at 45 down to 35mph for an average speed of 40.  Take some temp readings after each one.  You might have to adjust the speeds to fit the hill and your bus but you get the picture.  So come on, lets have a real world test or two!

Without an application pressure gauge it is hard to tell what is happening.   Old bus has one.  4107 does not yet. 

Don't put to much weight on government info/tests. They are written for the lowest common denominator, and I do mean LOW.    Example, the CDL handbooks and test suggest that a fully loaded truck will stop faster than an empty one.  Please don't start a debate on this.  I don't have 2 million miles with an 18 wheeler, but I do have enough to know that when it weighs 80k that it takes more room to stop than when it is 30K.  And yes I understand the control issues of brakes locking easier when empty.  If I have to bomb the brakes and there is a big rig in my mirrors, I'm hoping he is empty and has half a brain. 

Meaningless side note.  It always amazes me when people that would say government in general is inept at most things site them as the authority to support an argument. 

Want to muddy the waters even more?  How does each braking style affect buses with trailers/toads with various braking systems?   Are your auxiliary vehicles brakes balanced with the bus brakes?  Is one carrying more of the braking load?  Should you change your braking style with toad? 

If you start down the hill at a reasonable speed with good brakes and use what ever braking style you like there should be no drama.  If there is, the only solution is going slower.

Don 4107

[Jerry Liebler]

Don
    The tests you propose are good.  I don't know when or where but I'll probably try them.  They are what the U of M allegedly did.   The reccomended snub braking technique only uses a 5 MPh variation, you've proposed 10, I believe that is enough to clearly show that snub braking actually produces HOTTER brakes if the vehicle has well balanced brakes.  It doesn't change the fact that if your brakes get too hot you were going too fast.
Regards
Jerry 41`07 1120

[TomCat]

OK, this sounds like a good idea for an episode of "Mythbusters".
Two similar bus/trucks go down a hill, using each braking method, and have drum temps measured once at the bottom.

Anyone have an in to "Mythbusters"?

Jay
87 SaftLiner

[Chaz]

Thanx Jack and Tom!!! I have yet to do the "mountains", so I really appreciate the insight for my automatic.

  Just curious......... If I'm out and about, and not really knowing the terrain, what % or sign or ?? do I watch for, so as to know when I have to be implimenting all this new found knowledge?? Here in Indiana, there are a few decent sized hills, but not too many. But I do plan to go to Bristol for the spring race! (I-75 south, 25E, etc.)  

    Thanx guys,
       chaz

 p.s. good thought Jay!!

[RJ]

Chaz -

The easiest is to simply pay attention to the signs posted for truckers.  Usually they're yellow, but sometimes orange or white, all with black lettering.  Keep w/in those guidelines and you'll be a happy (and safe!) camper.

FWIW & HTH. . .

 

[TomC]

In my opinion-and this from 1.3 million miles of driving over 21 years of owner/operator (my own truck).  When going down ANY kind of long grade, you should be in full control.  That translates into the fact that you should only have to use a very light brake pedal pressure to keep the truck at speed-this involves being in the right gear going the right speed-whether or not you have a Jake brake.  If you smoke the brakes-you're going to fast!  I can go down the Grapevine without touching the brakes at 60mph with just the Jakes.  If I didn't have Jakes, I'd be going down the hill in a lower gear with the trucks at 35mph-but still under control and not smoking the brakes.  If you have to constantly have to drag your brakes going down the hill, you're going to fast. 

If you're going down the hill at the correct speed in the right gear, you should be just barely accelerating so that you go a minute or two without brakes, then a very light application of brakes for about 20 seconds will bring you back down to speed.  With this technique, you can go down a 100 mile hill and not overheat the brakes (I'd like to see that grade!).  And this from a trucker that got 350,000 miles on a set of brakes.  My truck has 1.2 million miles on it.  I did a brake job at 355,000 miles, then at 775,000 miles then at 1,050,000 miles.  Now at 1.2 million miles they still have about 20% brakes left.  With the size of the brakes on the buses and our relatively light loads, if you smoke the brakes or can smell them, you need to rethink you're braking techniques.  Good Luck, TomC