Air Bags

P

phil swanson

New member
Jan 7, 1998
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You wrote: The manuals are very specific about not driving with the
controls in hold. Depending on the driving conditions, speed etc an
overload condition can develop on the front tires.

My air system in my '73 is completly inoperable. When I bought it a
year ago, I put valves at the bags and filled them to 85 lbs and they
have been there ever since. Have not had any ill effects that I can
tell. Don't know what all the fuss is about. One of these days I will
get around to re-doing the system but not a very high priority.

Phil Swanson
 
I was looking at my 22-year-old, weather-checked air bags this morning and
wondering if I should spray them with a rubber preservative such as 303 or
something. Good idea? Bad idea?

Richard Guthart
'77 Birchaven
 
On Tue, 1 Dec 1998 05:25:47 -0700 "Richard Guthart"
writes:
>I was looking at my 22-year-old, weather-checked air bags this morning
>and
>wondering if I should spray them with a rubber preservative such as
>303 or
>something. Good idea? Bad idea?
>
>Richard Guthart
>'77 Birchaven
>
Richard, if they are original air bags (and I doubt it) a really good
idea would be to replace them cause when they blow they will take
something else out with them.

I may not be the only one who thinks this.

David Lee Greenberg
GMC Motorhome Registry
200 MacFarlane Dr PH4N
Delray Beach, FL 33483-6829
561/243-0402
 
Are you sure they are 22 years old? Quite possibly they have been replace.
The air bag is replaceable. One of the important places to lean is around the
metal at each end. I think these to be aluminum but they will collect mud,
road dirt, rocks etc. This in turn causes chaffing around the rubber bags in
this area. When I stop I check these places and clean them off. The more
dirt or gravel on the road the more I would stop to check them. If there is
no signs of cracks or chaffing of the rubber I would be pretty hesitant in
spraying anything on them. Maybe the Environmental Tech's Rubber or Dri Wash
and Guard. The rest of the products out there seem to help deteriorate the
rubber. You can see this when you spay it on and actually see the rubber or
discoloration of the rubber taking place. Do keep the metal that goes into
the bags clean and free of the dirt. One of the things to do on the bags is
to block the boogies, lower the air pressure, loosen the bolts that hold them
and rotate the bags one quarter or one half turn. This will help reduce the
pressure that is called hot dogging the bags. In addition to this you might
consider blocking the center of the wheel area, boogie when you are parked and
relieve the air from the bag to ensure no pressure. This I have been told
helps too. Chuck

> I was looking at my 22-year-old, weather-checked air bags this morning and
> wondering if I should spray them with a rubber preservative such as 303 or
> something. Good idea? Bad idea?
>
> Richard Guthart
> '77 Birchaven
 
Since the topic is air bags. Where is everyone getting them? I need two new
ones with aluminum cones.

>-- [ From: Eugene Fisher * EMC.Ver #2.5.3 ] --
>
>not a good idea. Look up on the web site for some bag suggestions
>
>http://www.california.com/~eagle/
>
>gene
>
>-------- REPLY, Original message follows --------
>
>Date: Tuesday, 01-Dec-98 07:29 AM
>
>From: Richard Guthart \ Internet: (rguthart)
>To: gmclist \ Internet: (gmcmotorhome
>.org)
>
>Attachment: mimemsg.doc Code: 01IVOA7 \ Created: Unknown [2 Kb]
>
>Subject: GMC: air bags
>
>I was looking at my 22-year-old, weather-checked air bags this morning
>and wondering if I should spray them with a rubber preservative such as
>303 or something. Good idea? Bad idea?
>
>Richard Guthart
>'77 Birchaven
>
>
>
>-------- REPLY, End of original message --------
>
>
>--
>Gene 76Palm Beach /Or/CA
>
>GMC Technical Information http://www.california.com/~eagle/
>
>
Tom & Marg Warner
Vernon Center NY
1976 palmbeach
 
Buskirks got a new shipment in last month! Give them a call.

>
> Since the topic is air bags. Where is everyone getting them? I need two new
> ones with aluminum cones.
>

> >-- [ From: Eugene Fisher * EMC.Ver #2.5.3 ] --
> >
> >not a good idea. Look up on the web site for some bag suggestions
> >
> >http://www.california.com/~eagle/
> >
> >gene
> >
> >-------- REPLY, Original message follows --------
> >
> >Date: Tuesday, 01-Dec-98 07:29 AM
> >
> >From: Richard Guthart \ Internet: (rguthart)
> >To: gmclist \ Internet: (gmcmotorhome
> >.org)
> >
> >Attachment: mimemsg.doc Code: 01IVOA7 \ Created: Unknown [2 Kb]
> >
> >Subject: GMC: air bags
> >
> >I was looking at my 22-year-old, weather-checked air bags this morning
> >and wondering if I should spray them with a rubber preservative such as
> >303 or something. Good idea? Bad idea?
> >
> >Richard Guthart
> >'77 Birchaven
> >
> >
> >
> >-------- REPLY, End of original message --------
> >
> >
> >--
> >Gene 76Palm Beach /Or/CA
> >
> >GMC Technical Information http://www.california.com/~eagle/
> >
> >
> Tom & Marg Warner
> Vernon Center NY
> 1976 palmbeach
 
Dave, I have no way of knowing for sure if they are the originals, though
that is what I was told by the previous owner. The coach has 56,000 miles on
it.
It's a '77 with (I presume) the metal cones.

When I bought it in July, one of my first thoughts was to replace the air
bags since they are such a vital component. But then I talked myself out of
it, after going through the archives of this list. I thought I was reading
that it would be very unusual for the bags to blow out (except for the early
ones whose plastic cones could shatter.) Rather, they would just start to
leak down one day and that would be the time to replace them.

Did I get the wrong impression or is this one of those areas of debate
within the GMC community? If they do become more prone to blow-outs with
age, what is their useful safe life before they ought to be replaced?

Dick Guthart

>Richard, if they are original air bags (and I doubt it) a really good
>idea would be to replace them cause when they blow they will take
>something else out with them.
>
>I may not be the only one who thinks this.
>
> David Lee Greenberg
>GMC Motorhome Registry
>200 MacFarlane Dr PH4N
>Delray Beach, FL 33483-6829
> 561/243-0402
>
 
Dick,

IIRC, there was some talk in the GMCMI newsletter or the GMCMM magazine
several years ago. HEY ARCH, POSSIBLE MYTH ALERT! When we got our '73 it
had the plastic cones. I assume they were original since the cones had
never been changed to metal ones. We drove it (towing the trailer with
probably about 1,500-2,000 lbs of tongue weight) for a few years with no
problems. After constantly hearing all the warnings about the plastic
cones, we finally gave in and got new bags with metal cones. Guess what.
One of the new bags had a leak (yes it was the bag and not the fittings),
leaked down on the test trip, rubbed the tire and wore a hole right through
it. We had successfully created a problem when there wasn't one to begin
with! We ended up putting one of the originals back in a driving with it
for a while before getting another replacement bag. We tested this one
with a schraeder valve under water before installing it though :).

This "problem" seems very similar to the wheel bearing failures. Everyone
seems to "know" someone that has had one "blow up", but not many have
actually had it happen to themselves. I think I have heard that Wes from
Cinnabar even says that even bags that look pretty bad are probably still
fine since the rubber is really just a protective coating. Of course the
note from Scott that Wes is not an official distributor of the airbags may
shed some light on this!

Arch, do I dare ask if anyone on the list has had actually had an air bag
"blow up" on their GMC? :)

Zak

>Dave, I have no way of knowing for sure if they are the originals, though
>that is what I was told by the previous owner. The coach has 56,000 miles on
>it.
>It's a '77 with (I presume) the metal cones.
>
>When I bought it in July, one of my first thoughts was to replace the air
>bags since they are such a vital component. But then I talked myself out of
>it, after going through the archives of this list. I thought I was reading
>that it would be very unusual for the bags to blow out (except for the early
>ones whose plastic cones could shatter.) Rather, they would just start to
>leak down one day and that would be the time to replace them.
>
>Did I get the wrong impression or is this one of those areas of debate
>within the GMC community? If they do become more prone to blow-outs with
>age, what is their useful safe life before they ought to be replaced?
>
>Dick Guthart
 
I saw lots of them at Golbys in Feb but was wondering if there was another
place.

>In a message dated 12/1/98 8:40:25 PM Eastern Standard Time, powerjon
>writes:
>
>> Buskirks got a new shipment in last month!
>
> Buskirk and Gateway are from what I have learned are the only two
>distributors for the air bags which Firestone makes. I was surprised
>Cinnabar was not a distributor which means Cinnabar buys from either Gateway
>or Buskirk?
>
>Scott Adohen .
>
>
Tom & Marg Warner
Vernon Center NY
1976 palmbeach
 
After eleven years one air bag blew at AM while parked in my garage at my
home. No obvious reason for the failure. We have driven over 100,000 miles
since then without a leak or problems of any kind.

Bob
mccarthy
 
Hardly an expert on air bag life expectancy. The only one that ever gave
me trouble in 23 years was nicked by the jack. I carry a spare but
probably won't need it for a while.

After the problem a blown tire caused I am wary of anything that could
blow another hole in the side of my coach.

BTW, I did put air bag lifters on and I think they save the bag from
going when the tire blew!

David Lee Greenberg
GMC Motorhome Registry
200 MacFarlane Dr PH4N
Delray Beach, FL 33483-6829
561/243-0402
 
Sirums has plenty of new ones as well as some used bags.

David Lee Greenberg
GMC Motorhome Registry
200 MacFarlane Dr PH4N
Delray Beach, FL 33483-6829
561/243-0402
 
Guys,

I haven't had a bag blow but can attest to the fact that the plastic cones
can explode. Mine spread pieces of plastic as far as the garage roof.
Luckily I was standing to the side so didn't get hurt. So if yours still has
the plastic cones be very careful when working around them.

This was the cone not the bag but I think some pieces are still in my shop
somewhere if we have any non believers. These things are even worse than
second hand smoke!

Dick Kennedy

Date: Wed, 02 Dec 1998 00:51:04 -0500
From: Zachary Zehnacker
Subject: Re: GMC: air bags

Dick,

IIRC, there was some talk in the GMCMI newsletter or the GMCMM magazine
several years ago. HEY ARCH, POSSIBLE MYTH ALERT! When we got our '73 it
had the plastic cones. I assume they were original since the cones had
never been changed to metal ones. We drove it (towing the trailer with
probably about 1,500-2,000 lbs of tongue weight) for a few years with no
problems. After constantly hearing all the warnings about the plastic
cones, we finally gave in and got new bags with metal cones. Guess what.

This "problem" seems very similar to the wheel bearing failures. Everyone
seems to "know" someone that has had one "blow up", but not many have
actually had it happen to themselves. I think I have heard that Wes from
Cinnabar even says that even bags that look pretty bad are probably still
fine since the rubber is really just a protective coating. Of course the
note from Scott that Wes is not an official distributor of the airbags may
shed some light on this!

Arch, do I dare ask if anyone on the list has had actually had an air bag
"blow up" on their GMC? :)

Zak
 
No Myth alert here! The plastic cones are a safety hazzard! The fact
that you have so many years of service out of the plastic cones is plain luck.

>
> Guys,
>
> I haven't had a bag blow but can attest to the fact that the plastic cones
> can explode. Mine spread pieces of plastic as far as the garage roof.
> Luckily I was standing to the side so didn't get hurt. So if yours still has
> the plastic cones be very careful when working around them.
>
> This was the cone not the bag but I think some pieces are still in my shop
> somewhere if we have any non believers. These things are even worse than
> second hand smoke!
>
> Dick Kennedy
>
> Date: Wed, 02 Dec 1998 00:51:04 -0500
> From: Zachary Zehnacker
> Subject: Re: GMC: air bags
>
> Dick,
>
> IIRC, there was some talk in the GMCMI newsletter or the GMCMM magazine
> several years ago. HEY ARCH, POSSIBLE MYTH ALERT! When we got our '73 it
> had the plastic cones. I assume they were original since the cones had
> never been changed to metal ones. We drove it (towing the trailer with
> probably about 1,500-2,000 lbs of tongue weight) for a few years with no
> problems. After constantly hearing all the warnings about the plastic
> cones, we finally gave in and got new bags with metal cones. Guess what.
>
> This "problem" seems very similar to the wheel bearing failures. Everyone
> seems to "know" someone that has had one "blow up", but not many have
> actually had it happen to themselves. I think I have heard that Wes from
> Cinnabar even says that even bags that look pretty bad are probably still
> fine since the rubber is really just a protective coating. Of course the
> note from Scott that Wes is not an official distributor of the airbags may
> shed some light on this!
>
> Arch, do I dare ask if anyone on the list has had actually had an air bag
> "blow up" on their GMC? :)
>
> Zak
 
John,

My main thinking behind the myth idea was the airbags themselves. I was
not really talking about the plastic cones. GM/Firestone came up with a
fix for that problem so it obviously was not just a myth. I used our
experience with the plastic cones to demonstrate that even the worst case
situation airbag lasted over 20 years without failing. I agree that the
plastic cones should probably be replaced with new cones. Most already
have. The original poster that I replied to had the metal cones.

How many 25 year old pieces of plastic shouldn't be replaced? I don't
think the plastic cones should be expected to last any longer than they do.
They are plastic. They take quite a bit of abuse. Ours were over 20
years old and had more loading for some of those years due to towing a
trailer. Were we lucky? I don't know. Did they last that long for us? Yes.

People have heard the stories about the plastic cones and assume all the
air bags are prone to failures. I don't think that is true with the metal
cones, and I think that this is where the problem turns into a myth. It
seems to be the plastic cones that are the problem, a problem that was
solved by changing them to aluminum. What do you think?

Zak

>No Myth alert here! The plastic cones are a safety hazzard! The fact
>that you have so many years of service out of the plastic cones is plain
luck.
>
 
Arch,

That one was a plastic cone failure not really an airbag failure. Since
GM/Firestone changed to aluminum cones, I'm inclined to agree that the
plastic cones probably should be replaced with the new ones. Actually, I
would have to think that most already have the metal cones. Therefore, I'm
more interested in air bag failures.

There has been one report so far of an airbag failure while the vehicle was
stationary with no known cause. There was another that went because a
system failure caused higher than acceptable pressures. The failure while
stationary part is interesting to me. I would think that the bags would be
much more likely to fail while the vehicle was going down the road. We'll
have to wait for more reports to get a better idea. Maybe as long as we
drive them all the time, we won't have any problems :). Of course we have
to have the E rated tires to do this, otherwise we have to keep it parked
to avoid tire failure :). Stop! Go! Stop! Go! I'm starting to sound like a
Pennzoil commercial.

Zak

>Zak
>
>Now there is one. Are you keeping track? Your report will be due at
>the end of the semester.
>
>Take Care
>Arch
>
>>
>> This was the cone not the bag but I think some pieces are still in my shop
>> somewhere if we have any non believers. These things are even worse than
>> second hand smoke!
>>
>
 
By the way, I did find out the air bag pressure that is necessary to support
my coach at normal ride height: left 95 lbs, right 85 lbs.

This is with minimum load.

In the 23' Birchaven the genset and kitchen module are on the left while the
potable water tank, water heater and blackwater waste tank, all of which are
empty at this time, are on the right.

Confirms what Rick Staples and others were suggesting.

Richard Guthart
'77 Birchaven
 
>
> No Myth alert here! The plastic cones are a safety hazzard! The fact
> that you have so many years of service out of the plastic cones is plain luck.
>

I wonder if the group would speculate or know why GM never did a recall
on these exploding OEM plastic air bag cones. There sure have been a
recalls on various vehicles for various problems over the years that
seem to me are much less a hazdard than flying shrapnel from a GMC wheel
well.

Phil Stewart
'76 Transmode
TN
 
I haven't read the Dec article in the Cinnibar Newsletter and I
suspect it is excellent based on the quality of other newsletters and
articles. I am going out on a limb and assume the author never used air bag
risers/lifters and therefore is only making theoretical comments.

I asked a lot of questions before putting a set on in early 1996 or
about 13,000 miles ago. Non-users were against them having not used them.
Those that had substantial experience with them on either didn't notice any
difference or some difference.

The air bag pressure is reduced from around 95 psi to about 72 - 75
psi. Somewhat less dangerous and damaging if and when a bag explodes. The
air pressure regulator can be reset from a maximum of 120 psi to 100 psi -
that took 30 to 40 seconds off total pump up time. The air pump doesn't have
to labour that last difficult 20 psi.

I contend there is only one suspension change and it's an improvement
with risers/lifters installed. The lower air pressure is off set by the
increased control arm length and mechanical advantage - no change in ride.
There is no change when lowering the coach. I think it may not go as high
but has not been a noticeable problem in campground levelling. I believed I
detected less sway since installing the risers and asked others for their
opinion. Some noticed no change. Some felt there was less sway, and like I,
could not explain it. Here is a possible reason there is less sway in my
opinion. The air bag cones cause progressive dampening as the two ends of
the bag are forced further and further to the wider parts of the cones. With
risers on, the bag is on a narrower part of the cone at the same ride height
as before - more force is required to move the air bag from a narrower part
to the wider part, producing more dampening or less sway.

I would be interested in other opinions and experiences.

Al Hamilton
76 Eleganza II

Kingston, Ont
 
The Cinnabar article isn't from a December issue. It's from their September
1998/Issue 17, p. 1. The article, titled an Engineer's Perspective, was
authered by Chuck Aulgur.

The article is referring to Leigh Harrison's four-air bag suspension system,
and does not include any supporting data, only opinions. You know what they
say about opinions, they're like r___ ends, everybody's got one. It does
not address air bag lifters.

I also suspect Al's opinion about the author is correct.

I installed the four-air bag system during the GMCMI Myrtle Beach Rally in
March 1995 at the same time as I installed Leigh's six-wheel disc brake
system. As I said the other day in response to an e-mail message asking
about the wear of carbon metallic brake pads, I have over 40,000 miles
experience with the system. Compared to the original, I notice a definate
increase in the fore-to-aft dampening of the ride, and much greater
stability in truck-rutted asphalt paving. I can't even feel the difference
when the coach drifts over the joint between the roadway and paved
shoulders, and have demonstrated such with folded arms not even holding onto
the steering wheel at the time. When I drift onto an unpaved shoulder,
there is no problem recovering. I haven't met anyone yet, without Leigh's
system, who feels very comfortable in running off the edge of the road.

Leigh also claims that the rear-rear axel spring rate is doubled to around
815 psi, compared to the original. This in turn, makes the brakes on the
axel able to exert more stopping ability prior to lock-up (which I've never
experienced thus far).

If you already haven't heard it in a few previous e-mail messages, the
original air bags are rumered soon to be in short supply, as the molds used
to make them are supposedly near the end of their life. Then what are you
going to do??????

I would encourge any doubting Thomas's to go with Leigh during the GMCMI
rallie's, when he routinely takes people for a demonstration ride. You
can't believe the stability his coach demonstrates.

Paul Bartz

From: The Hamiltons
Sent: 12/25/98 8:16 PM
Subject: GMC: Air Bags

I haven't read the Dec article in the Cinnibar Newsletter and I
suspect it is excellent based on the quality of other newsletters and
articles. I am going out on a limb and assume the author never used air
bag
risers/lifters and therefore is only making theoretical comments.

I asked a lot of questions before putting a set on in early 1996
or
about 13,000 miles ago. Non-users were against them having not used
them.
Those that had substantial experience with them on either didn't notice
any
difference or some difference.

The air bag pressure is reduced from around 95 psi to about 72 -
75
psi. Somewhat less dangerous and damaging if and when a bag explodes.
The
air pressure regulator can be reset from a maximum of 120 psi to 100 psi
- -
that took 30 to 40 seconds off total pump up time. The air pump doesn't
have
to labour that last difficult 20 psi.

I contend there is only one suspension change and it's an
improvement
with risers/lifters installed. The lower air pressure is off set by the
increased control arm length and mechanical advantage - no change in
ride.
There is no change when lowering the coach. I think it may not go as
high
but has not been a noticeable problem in campground levelling. I
believed I
detected less sway since installing the risers and asked others for
their
opinion. Some noticed no change. Some felt there was less sway, and like
I,
could not explain it. Here is a possible reason there is less sway in my
opinion. The air bag cones cause progressive dampening as the two ends
of
the bag are forced further and further to the wider parts of the cones.
With
risers on, the bag is on a narrower part of the cone at the same ride
height
as before - more force is required to move the air bag from a narrower
part
to the wider part, producing more dampening or less sway.

I would be interested in other opinions and experiences.

Al Hamilton
76
Eleganza II

Kingston, Ont
 
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