Mountain Driving and Downhill Braking

[mogul264]

Originally Posted by Britbiker

I have to agree with this. I've driven many miles in ready mix concrete trucks, dump trucks and 18 wheelers full of wood chips equipped with air brakes. The variables in application times, foundation brake hardware, and valving in an air brake system make them far less efficient than hydraulic brakes. Also, liquids cannot be compressed, so the brake fluid in a hydraulic system acts almost like a solid column pressing on the pistons as opposed to air which can be compressed adding a bit of sponginess to the pedal IMHO.

Actually, 'air' brakes do NOT use air as the actual force to actuate the brakes. Air RETRACTS the brakes from the wheel. Which is why an air-brake vehicle, set for a long period, its stored air leaks down. Air must be built back up by a compressor on the engine, before the vehicle can then be moved. Springs clamp the brakes to the wheel, UNTIL retracted. The 'parking brake' (pulling the red button) merely dumps air (that 'fisssh' sound) from the braking system, allowing the springs to apply the brakes! And YES, both brake types must be maintained to work properly!

[twinboat]

Originally Posted by mogul264

Actually, 'air' brakes do NOT use air as the actual force to actuate the brakes. Air RETRACTS the brakes from the wheel. Which is why an air-brake vehicle, set for a long period, its stored air leaks down. Air must be built back up by a compressor on the engine, before the vehicle can then be moved. Springs clamp the brakes to the wheel, UNTIL retracted. The 'parking brake' (pulling the red button) merely dumps air (that 'fisssh' sound) from the braking system, allowing the springs to apply the brakes! And YES, both brake types must be maintained to work properly!

Air brakes absolutely do use air to apply the brakes.

What your describing is just the parking brake used on one axle of a motorhome for parking.

The service brakes are on all axles and use air to apply the brakes for normal stopping.

[Prof.Gadget]

In Colorado at least. When the pretty Yellow sign says Trucks use lower gears and especially if they post a speed limit for Trucks. That means you.
As a general rule If you are on a long incline and you take your foot off the gas the vehicle should maintain it's current speed or slow down. If you constantly have to use the brakes to maintain your speed you should be using a lower gear and going slower.

Originally Posted by araghunathan

Hi yall - new to the forum and RV driving. Have a lot paranoia related to mountain driving and brake glazing. We have an 38' RV converted from a school bus. We're about 26000lbs, Cummins ISB5.9 with an Allison 4 speed transmission, air brakes, but no jake or exhaust brakes. We're heading thru AZ later this month and will be driving on I17 to and from Camp Verde up to the Cottonwoods Campgrounds. The Mountain Directory says '6% grade for 7 miles". Do yall have suggestions for safe speeds/gear (2nd or 3rd) to maintain for that length of descent with my rig capabilities and any other strategies for navigating these and future downhills?

Any advice will be greatly appreciated. Thanks in advance.

-Anand