Suspension lean solved...what I learned

[Scott Forman]

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

[fwernlein]

Good logical observation....i'll file this useful info for when I
have this issue come up!

Thanks!

Frank W.
Woodbridge, VA.
85FC33


--- In WanderlodgeForum@yahoogroups.com, "Scott Forman"
<sforman@r...> 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
>

[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
>
>
>
>
>
>
>
>Yahoo! Groups Links
>
>
>
>
>
>
>
>
>
>
>

[Tom Warner]

Only one small observation Scott. The airbag is only composed of a
single bladder. It is a canvas bladder coated on the inside and
outside with rubber. The outer rubber coating is only used to
protect the bladder from the elements. It will hold air fine even
with the outer covering missing.

Tom Warner
1982 FC35
Vernon Center,NY

At 09:17 AM 1/19/2006, you 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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[Gregory OConnor]

Scott, maybe it was the distorted bag. weak tires fill taller with
the same air pressure

Greg
pt40 Romoland California

.a > 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
> >
> >
> >
> >
> >
> >
> >
> >Yahoo! Groups Links
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
>