Air Dump Revisited


Airbag 1
One example of an air bag
Airbag 2
Another variety of airbag.

A certain percentage of RV’s are equipped with systems that dump the air out of the RV airbag suspension system.  They are optional (so far as I know) both as to whether they are included in the original build and whether they should be used.

I have been very schizo about our airbags and our air dump system.  Journey had them and I used them about 1/2 the time.  Serendipity has them and I have hardly ever used them.   The Winnebago system uses 4 airbags.  The Holiday Rambler system uses 8 airbags. They are much more comfortable to ride in than a spring suspension but I haven’t been thinking much about air bags when it comes time to park.

The Holiday Rambler owners manual says that the air dump system may  be used to assist with leveling the coach when  you are parked. However, the manual says nothing about how to use it.

In case any of you aren’t familiar with why leveling your RV when parked is important here’s the short, short, short version:  
aside from feeling funny when you walk around inside an un-level RV, the Norcold and Dometic refrigerators in many of the RV’s need to be level in order to work properly.  So, in addition to feeling goofy walking down hill, or uphill, or sideways — you want to keep your RV level so that your food cools correctly.

Our dealer actually discouraged using the air dump system out of concern for the life of the airbags — saying that without air pressure it’s possible to cause premature wear on the bags themselves. I don’t know if that’s a legitimate concern but it has weighed on whether I chose to use the air dump system.  If anything I’d rather be less comfortable and more maintenance minded than the other way around.

The last several times we have moved I have been playing around with the air dump system.  For one thing I’ve been determining how much lower to coach sets with the air bags dumped before leveling. Learning to let the air dump to release some of the air but not all is one possibility.  Then, the jacks raise the coach up again activating the inflate/deflate valves.  I have noticed that when I extend my jacks without dumping the air the air bags deflating partially on their own.  That process of relieving the pressure on the bags causes the bags to partially deflate on their own.

Then there are the mechanical realities of a 40’ long suspension system.  Our Winnebago Journey had a four leg leveling system, our Holiday Rambler Ambassador has a three leg system (2 in the back, 1 in the front).  No matter how many legs you have, the leveling system can bind — caused by the twisting of the frame and suspension components — the weight of the coach pushing down on the axles and the pushing up of the leveling legs.  The rear wheels on an air brake RV are the only wheels that are locked when parked.  Too much lift or a twist on the frame not mimicked when you retract your levelers can produce a state where when you retract the legs. They will bind, usually accompanied by a nasty CLUNK when they release.

NOTE:  If you have a three jack leveling system you should always extend the FRONT jack first.  Doing so will relieve the stress on the steering axle and will act as a pivot point for the other two jacks.  Failing to do so will cause even more torquing (twisting) of the frame.  When packing up to move, reverse the process and lower the rear jacks first and finally the front jack.

I have noticed is that by dumping air before leveling I prevent that uneven bind and the loud clunk.  The reason is simple.  Dumping the air lowers the coach.  The lowered coach doesn’t have to be raised as far to be leveled.  And as soon as you crank up the engine the first thing it’s going to do is to rebuild your air supply — re-inflating the airbags.  Once the bags inflate, there isn’t nearly as much weight on the legs and no binding. Voila!  Simple.

The other advantage of dumping is that you don’t need a supplementary step or footstool because your coach isn’t sitting quite as high.  The older we get as RV’ers the more concerned we are about safety; and stepping down two steps instead of three is definitely a good idea.

So, I think we’ll use our air dump more than we have.  I’ll dump some of the air, but not all.  Keeping a little pressure in the bags can only be a good thing from the maintenance standpoint.

And, I’ve learned a little more about our coach.

Thanks for stopping by, and I’ll talk with you tomorrow.

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