Downhill Grades With A Bus

Rudy · Post by **Rudy** » Wed Mar 02, 2011 2:16 pm

My lack of driving experience with my bus ( perhaps two hours ) has prompted to ask some advice.

I don't quite know what is the proper approach to safely go down a long grade.

The bus has an eight cylinder CAT motor in the front. It has air brakes. It has an Allison 4 speed automatic transmission.

My primary question is: Should I put the transmission in third gear in anticipation of a long run downhill?

I am concerned about the available air to keep my brakes functioning.

At an idle, if I depress the brake pedal 12 to 15 times all the way down in a quick succession, I can get the gage to buzzer in at 30 lbs. I have no clue if that is normal.

Those two items would be handy to know about.

Please help me with some answers. Thanks

Rudy

Post by **stuartcnz** » Wed Mar 02, 2011 2:36 pm

General rule of thumb in trucks is to use the same gear going down a hill, as you would use to climb it. If you don't have any exhaust or engine brakes, you may want to go a gear lower still.

Either way go down hills SLOWLY!

PS. you don't want your brakes getting to hot, wich is why you want to use a low gear, that way you don't spend so much time on the brakes. You want them to be cold when you need them.

Bob · Post by **Bob** » Wed Mar 02, 2011 2:57 pm

Put it in low and go slow! Besides getting your brakes hot you could very easily run low on air and have no brakes. (I've been there) The Allison transmission is a great beef-monster!

ezrablu · Post by **ezrablu** » Wed Mar 02, 2011 3:17 pm

Rudy, maybe ya better wear a Depends just in case the "low and slow" method don't pan out

somewhereinusa · Post by **somewhereinusa** » Wed Mar 02, 2011 3:52 pm

What the others said. A diesel, without an engine retarder of some kind, doesn't really have any back pressure (no throttle plate) to slow you down. I wouldn't use low, depending on grade and length of hill, assuming you have a 4 speed, pick 2 or 3. Watch the tach, keep the rpm's down, when it rises get on the brakes hard ( don't lock them up) to bring speed down fast and get off the brakes. This helps brake cooling and gives the compressor time to build air again. Don't ride the brakes, it makes them hot. Hot brakes don't work. You should'nt see smoke, if you do they are too hot pull over and let them cool. Most trucks loose brakes from heat not lack of air.
Rudy if you're going to Chatanooga, Mt Eagle is one of the worst in the country in my opinion. I did find an 11% grade on some back road in PA last week.

You'll be fine, just use some common sense.

Dick

Rudy · Post by **Rudy** » Wed Mar 02, 2011 4:08 pm

WOW! Thanks for all your input. You have given me strength.

Here's an idea:

Imagine if you had many 2 foot by 2 foot metal plates in a line mounted along each side of the bus that were hinged in the rear of each plate. If you connected each plate with a rod, you could deploy them open all at once.

It would create a tremendous wind resistance which would greatly slow down the bus much like a parachute slows down a dragster.

Orbit told me that was an awesome idea.

Rudy · Post by **Rudy** » Wed Mar 02, 2011 4:12 pm

Dick, my bus does not have a tachometer. I would buy one if I knew how to hook it up.

Bob · Post by **Bob** » Wed Mar 02, 2011 4:13 pm

Several times I have driven the route that you will be taking...not even many hills. I'd still wear the depends though...you will make better time without stops.

Rudy · Post by **Rudy** » Wed Mar 02, 2011 4:14 pm

ezrablu wrote:Rudy, maybe ya better wear a Depends just in case the "low and slow" method don't pan out

Blu, I am still quite continent. I might freak out on a white knuckle flight downhill and pop an eyeball out, though.

Rudy · Post by **Rudy** » Wed Mar 02, 2011 4:18 pm

Bob wrote:Several times I have driven the route that you will be taking...not even many hills. I'd still wear the depends though...you will make better time without stops.

Bob, that would make the perfect compliment to my Peenie Tube to the gallon jug.

Rudy · Post by **Rudy** » Wed Mar 02, 2011 4:21 pm

stuartcnz wrote:General rule of thumb in trucks is to use the same gear going down a hill, as you would use to climb it. If you don't have any exhaust or engine brakes, you may want to go a gear lower still.

Either way go down hills SLOWLY!

PS. you don't want your brakes getting to hot, wich is why you want to use a low gear, that way you don't spend so much time on the brakes. You want them to be cold when you need them.

Stuart, what you said about using the same gear going downhill as the gear going uphill makes such beautiful scientific sense. You are a genius.

somewhereinusa · Post by **somewhereinusa** » Wed Mar 02, 2011 4:25 pm

Rudy wrote:Dick, my bus does not have a tachometer. I would buy one if I knew how to hook it up.

Just take the engine cover off and count the fan revolutions, divide by how many blades are on the fan, add 3, count passing power poles and subtract 10.

Rudy · Post by **Rudy** » Wed Mar 02, 2011 4:31 pm

Dick, that's awesome. Do you think I should wear ear muffs?

ezrablu · Post by **ezrablu** » Wed Mar 02, 2011 4:54 pm

ok, now I'm sitting here laughing at this whole thread...and Rudy's life is at stake! I'm picturing Rudy strapping on a Depends, poppin up the hood up with a calculator in his hand

tamangel · Post by **tamangel** » Wed Mar 02, 2011 5:29 pm

look into getting a Jake Brake installed on your motor..

http://en.wikipedia.org/wiki/Jake_brake

and a vid of the sound..

http://www.youtube.com/watch%3Fv%3DUT4sHf1gYLI

FAQ's by the Jacobs company:

http://www.jakebrake.com/support/faqs.php

Mike

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Downhill Grades With A Bus

Downhill Grades With A Bus

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