Suspension lean solved...what I learned

[George Lowry]

Scott,

From my experience on WL's and other vehicles, I have seen two basic
installations on the height control valves for the front axle. On some,
they use the same height control valve as used on the rear and feed the
output from it into a "Tee" which then goes to the airbags. This
effectively ties the two sides together, allowing the air to flow from
one side to the other. Some others used a different control valve which
had two outputs, one for each side. This was supposed to both sides of
the front at the same pressures but did not allow free flow from one
side to the other as the "Tee" connection will do. I do not know what
type BB used at which period of time, however, from the description you
provided, it would appear that you may have the latter described valve
on your coach. Hope this helps with your understanding of the system.

George Lowry
'95 WBDA 4203 trading for a new Alpine Apex
Spearfish, SD Now in Quartzsite, AZ

Scott Forman wrote:

>Thought I would share my findings with the group regarding the
>leaning air suspension I have talked about here lately.
>
>I got the coach back yesterday after having a rough-looking airbag
>replaced on the left front (for review-the front axle was listing to
>the left while the rear was properly level). The old bag that was
>replaced appeared to still be holding air (no audible leaking noise
>and no bubbling when soaped), but did have a large tear in the outer
>bladder that had exposed the inner bladder to the environment.
>Holding air or not, I figured its days were numbered, so I opted to
>replace.
>
>The suspension now operates correctly. Since the only thing that has
>changed is the replaced bag, I have developed a theory on what was
>causing my lean:
>
>I suspect that the torn bag was seeping air even though I could find
>no evidence of it. As a result of this, I believe that when the
>suspension was airing up from a dump position and the front leveling
>valve was calling for air to lift the front axle, air would fill the
>right side bags faster than the left side, casuing the lean. The
>front leveling valve only knows up and down, not side to side, so it
>just keeps pumping until a height is reached. If it lifts unevenly,
>it doesn't care, it just wants to reach a height. So the right side
>was getting over-inflated before the left could catch up.
>
>Meanwhile, on the rear axle, the rear valves that control side-to-
>side were oblivious to what was happening. The lean was pronounced
>in the front, but 30 feet back at the rear axle, the lean was much
>less dramatic, so the rear valves, though functioning correctly,
>weren't adjusting enough to correct it.
>
>So that's my theory based on what I have learned. My escapades
>chasing gremlins in the air suspension have given me a lot of respect
>for the complexity and engineering that went into the system. It's a
>living thing...it breathes, it consumes, and when you can't find the
>problem, it seems like it hates. Many different things that all have
>to work together or the whole thing fritzes out.
>
>Scott Forman
>'Tiger Pride'
>82 FC35RB
>Memphis
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