Air Bag Rock and Roll

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June 2, 2008

A number of RVers have asked us how they can improve the ride and stability on airbag-equipped motorhomes-in particular, how they can stop that rocking motion that occurs when pulling into and out of driveways.

To understand the problem and how it can be solved, first we need to discuss the physics of the airbag itself, and how the air lines are plumbed.

On many systems, the air bags on one side are plumbed into the bags on the opposite side-so as the driver side bag(s) are compressed, for example, it dumps its air to the passenger side bag(s), setting off a rocking motion. Even on systems where the air does not go into the opposite bag, rocking can still be a problem.  Air bags have the rebound characteristics of a basketball, so once the rocking motion gets started, it can take a while to stop.

To help solve the problem, our team at SuperSteer worked with Don Yale of the Donvel Corporation to help us develop what we call a Motion Control Unit (MCU) for RV air bag suspensions. The concept is fairly straightforward-the MCU contains a baffle that controls the flow of air, which equalizes air pressure in the bags and helps prevent rapid fluctuation. The way the air flows into and out of the bags is crucial, because shocks and sway bars can only do so much. In fact, some coaches don’t even come equipped with sway bars, and to put them on is next to impossible in some instances. On coaches like this, MCU’s are pretty much the only solution, although coaches with sway bars may also benefit from the added control MCU’s provide. You may also elect to combine the MCU’s with a quality shock like the Koni FSD or the new RoadKing, which can further improve handling.

SuperSteer MCUs are available in varying rates of control

SuperSteer MCU's mount on the air bag line, as shown







Each MCU is only about the size of a shotgun shell, and is pretty easy to install. The air line is cleaned thoroughly and then cut, and the MCU is placed in line. Typically, the whole process takes about half an hour to 45 minutes per pair of bags.

One of the things we’ve learned recently is that we can add varying degrees of control using different MCU’s for the front and rear air bags. Typically, more sway is generated from the rear of the coach, so we can change the rate of control front-to-rear to achieve the desired results.






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