Aren't we supposed to dump the air bags before we slide the 5th wheel?

About a year ago, I was having trouble sliding my 5th wheel. I called breakdown because I thought I would need a mobile mechanic to come out and repair my 5th wheel. Breakdown wanted to walk me through the process of sliding the 5th wheel before they sent out a mobile mechanic. I always extended my landing gear to the ground when i would slide the 5th wheel, but after I told breakdown that the feet of the landing gear were on the ground, breakdown instructed me to keep extending the landing gear until I heard the air rush out of the air bags. So I continued extending the landing gear until I heard the air rush out of the air bags. Then I tried to slide the 5th wheel, and, lo and behold, it worked. The 5th wheel slid gently, and I was able to get the pins of the 5th wheel to line up exactly where I wanted them.

Previously, whenever I slid the 5th wheel, I did not dump the air out of the air bags, and sliding the 5th wheel was a very violent process. It was very difficult to slide the 5th wheel anywhere except all the way forward or all the way back. If I needed to slide the 5th wheel to somewhere in the middle, it would take me a long time, frequently over 30 minutes.

This made me a big believer in dumping the air out of the air bags when right before I slid the 5th wheel. Breakdown told me that there are two ways to dump the air out of the air bags: 1# extending the landing gear of the trailer until I heard the air rush out of the air bags or 2# pressing the "SUSP DUMP" button inside the cab of my tractor.

I recently bought the Delmar's Tractor-Trailer Truck Driver Training book. The book gives instructions on how to slide the 5th wheel on two pages. Neither set of instructions mentions anything about dumping the air out of the air bags before sliding the 5th wheel.

Here are photographs of the cover of the book and the pages of the book that give instructions on how to slide the 5th wheel:








Why didn't Delmar's Tractor-Trailer Truck Driver Training book instruct its readers to dump the air out of the air bags before sliding the 5th wheel?

 

Just out of curiosity, why wouldn't dumping the air out of the air bags help if it's a heavy load? Is it because if it's a heavy load, the weight of the trailer might be pushing down with so much force that dumping the air out of the air bags won't make it so there is zero load on the 5th wheel?

The fact that the authors of Delmar's Tractor-Trailer Truck Driving Training book didn't say to dump the air out of the air bags right before sliding the 5th wheel has made this book lose a lot of credibility in my eyes, unless someone here can give a good reason why dumping the air out of the air bags should not be mentioned in the instructions for how to slide the 5th wheel.

Furthermore, look at the first instruction: "Be sure to set the trailer parking brake before getting out of the cab--for any reason. This will prevent the tractor from rolling."----WHat?! Shouldn't that say be sure to set the TRACTOR parking brake, not the trailer parking brake?

I feel like maybe I should throw this book in the trash can.

 

The first instruction says "Be sure to set the trailer parking brake before getting out of the cab---for any reason. This will prevent the tractor from rolling."

The author must have meant the parking brake, but the first word of her description of the brake was trailer. The red brake valve is for the spring brakes on the trailer. People will associate any brake valve that says trailer on it with the red valve. The red valve even says "Not for parking" on it.

 

No. It said to set the trailer brakes so the tractor wouldn't roll, not so the trailer doesn't roll. The author didn't say what you're saying.

 

The book never even explicitly says to lower the landing gear to the ground in the first place. If you drop the air bags without the landing gear down, it won't take the pressure off the 5th wheel.

The book spells out everything else about the process instead of just letting it go without saying because it's common sense. So why not mention dumping the air bags?

 

What do you mean when you say you lower the landing gear to an inch off the ground so the fifth wheel is not hanging on the pin?