4 Air Bag rear suspension

jim bounds1

New member
May 18, 1998
2,067
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Fri. I installed another 4 air bag system and again made another GMC
owner pleased.

Other than a few testy bolts, the install went smoothly. I had the 2
pin bolts on the driver side put up a valiant struggle. I had a 3/4"
breaker bar lifting the coach via a 2 1/2ton floor jack before it
surrendered. I did not want to heat the nut unless I had no other
choise not wanting to risk the temper of the pin.

The kit fits purfectly, install time was 4 hours. I added seperate shut
off valves for each bag to give the system flexability. Paul Gibson,
head of Firestones Ride Rite division test drove the system and was
completely impressed. Paul was involved initially in the GMC rear
suspension design using the single 2 sided air bag. He was so impressed
that Firestone acknowledged the systems viability by designating it with
its own Firestone part #. This is not a gimick or fad, it is truly a
next step improvement in the evolution of a better ride for our
motorhome.

The customers drive test was impressive as the installation fit. All
the way home to Venice Fla., the customer said the coach tracked like it
was mounted to rails. He was concerned that the unusual handling
characteristics of the rear suspension would prevent his wife from
driving the coach. He stated that he can now travel at speeds that
would have concerned him before. He now has the confidence to take it
out on any 2 lane, grooved, multilevel road we wants.

Although the air compressor went into thermal when we were resetting the
tank pressure, it is adequite for operating the system under normal
conditions. I would like to experiment adapting some of the technology
I found when outfitting the air dump systems on ambulances I worked with
last year. They use a higher CFM compressor and "ping" tanks tied to
the air bags for more volume of air. A properly installed air drop
system on an ambulance can drop the suspension to the ground in 4 sec.
and reinflate the system to ride height in no more than 10 sec., a
pretty impressive control. I feel this would be a worthwhile
modification to the GMC air ride system and would like to set one up,
any takers out there?

The bottom line is, you really should investige the 4 air bag system if
you are going to be in the market for new air bags any time soon. It
costs a bit more than replacing the OEM bags, but with 2 bags costing
around $500.00, the cost of this tremendous performance modifcation is
not as far out of reach as it seems.

If you want to look further into this system, give me a call
(1-877-275-4462) or find someone who has installed the system and they
will surly support all I tell you.

Input on this subject is most certainly welcome.

Jim Bounds www.gmccoop.com
 
Jim:

As you know, I installed the system plus six-wheel disc brakes in Mar
1995 at/during the GMC MI Spring Rally in Myrtle Beach. It sure drew a
crowd all week long.

The four air bag system opens up another dimension of comfortable
driving and coach stability, dampening the fore-to-aft and side-to-side
movement of the coach while driving.

I agree completely with your below comments and also heartily encourage
all other coach owners to install the air bags. Make an appointment
with Jim.

Paul

> -----Original Message-----
> From: Jim Bounds [SMTP:jimbounds]
> Sent: Tuesday, June 02, 1998 2:06 AM
> To: gmcmotorhome
> Subject: GMC: 4 Air Bag rear suspension
>
> Fri. I installed another 4 air bag system and again made another GMC
> owner pleased.
>
> Other than a few testy bolts, the install went smoothly. I had the 2
> pin bolts on the driver side put up a valiant struggle. I had a 3/4"
> breaker bar lifting the coach via a 2 1/2ton floor jack before it
> surrendered. I did not want to heat the nut unless I had no other
> choise not wanting to risk the temper of the pin.
>
> The kit fits purfectly, install time was 4 hours. I added seperate
> shut off valves for each bag to give the system flexability. Paul
> Gibson,
> head of Firestones Ride Rite division test drove the system and was
> completely impressed. Paul was involved initially in the GMC rear
> suspension design using the single 2 sided air bag. He was so
> impressed that Firestone acknowledged the systems viability by
> designating it with its own Firestone part #. This is not a gimick or
> fad, it is truly a next step improvement in the evolution of a better
> ride for our motorhome.
>
> The customers drive test was as impressive as the installation fit.
> All the way home to Venice Fla., the customer said the coach tracked
> like it was mounted to rails. He was concerned that the unusual
> handling characteristics of the rear suspension would prevent his wife
> from driving the coach. He stated that he can now travel at speeds
> that would have concerned him before. He now has the confidence to
> take it out on any 2 lane, grooved, multilevel road we wants.
>
> Although the air compressor went into thermal when we were resetting
> the tank pressure, it is adequite for operating the system under
> normal conditions. I would like to experiment adapting some of the
> technology I found when outfitting the air dump systems on ambulances
> I worked with last year. They use a higher CFM compressor and "ping"
> tanks tied to the air bags for more volume of air. A properly
> installed air drop system on an ambulance can drop the suspension to
> the ground in 4 sec and reinflate the system to ride height in no more
> than 10 sec, a pretty impressive control. I feel this would be a
> worthwhile modification to the GMC air ride system and would like to
> set one up, any takers out there?
>
> The bottom line is, you really should investige the 4 air bag system
> if you are going to be in the market for new air bags any time soon.
> It costs a bit more than replacing the OEM bags, but with 2 bags
> costing around $500.00, the cost of this tremendous performance
> modifcation is not as far out of reach as it seems.
>
> If you want to look further into this system, give me a call
> (1-877-275-4462) or find someone who has installed the system and they
> will surly support all I tell you.
>
> Input on this subject is most certainly welcome.
>
>
> Jim Bounds www.gmccoop.com
 
Rick:

I installed the four air bag system in Mar 1995. Can't say enough about
it. You can't go wrong with it.

To install the four air bag kit, you remove the original air bag and
cones, install a steel "cage" on top of the center casting, an air bag
on each side of the cage, securing the opposite end of the air bags to
the swing arm, 'a la' the original air bag and reconnect the air lines
The kit comes complete with nothing else to purchase.

There is a slight reduction (approximately 1") in the suspension height
travel, but you probably wouldn't notice the difference and therefore,
to me, it's a non-issue.

The ride is significantly better and smoother. After all, now you have
independent suspension at each rear wheel. The rear-rear wheel spring
rate is doubled from approximately 415 psi to 820 psi, which results in
a much more stable coach ride and more effective braking (i. e. less
likelihood that the rear-rear tires will skid under severe braking
conditions). The fore-to-aft and side-to-side movement of the coach
driving down the road is dampened, normally without bottoming out the
shocks, particularly the front ones.

I don't notice any difference in air consumption.

There is no intrusion on tire clearance vs. the original bag.

The suspension loading remains essentially the same except for the
spring rate on the rear-rear axle, as noted above.

The kit originator is Leigh Harrison. Call him: 703-494-9914 for info
and literature. Tell Leigh I said Hi!

Paul Bartz

> -----Original Message-----
> From: RickStapls [SMTP:RickStapls]
> Sent: Tuesday, June 02, 1998 3:20 AM
> To: gmcmotorhome
> Subject: Re: GMC: 4 Air Bag rear suspension
>

>
> The bottom line is, you really should investigate the 4 air bag system
> if you are going to be in the market for new air bags any time soon.
> It costs a bit more than replacing the OEM bags, but with 2 bags
> costing around $500.00, the cost of this tremendous performance
> modification is not as far out of reach as it seems.
>
> Jim et al,
>
> I am intrigued by this system, especially with all the glowing
> testimonials. Where can I find out more info, especially:
>
> a. Does the 4-bag system use the stock suspension arms and shocks,
> and/or are they reinforced/replaced?
> b. Does it afford the full range of wheel travel and leveling that
> the stock system does?
> c. Does it provide as soft a ride as the stock system?
> d. Does it consume more air than the stock system (as seems to be
> implied in your post)?
> e. Does it leave at least as much clearance for oversize tires as
> does the stock suspension?
> f. Are suspension loads transferred to the frame approximately as
> in the stock system, and therefore is it able to withstand at least as
> much impact load (potholes) as the stock system?
>
> Most importantly, where can I find pictures, diagrams, and technical
> info on the 4-bag system? My position is all modifications are like
> UFOs: I have an open mind and am quite prepared to believe in them,
> but I need lots of hard facts before I can. (And LOTS of
> facts/details before investing all-too-rare dollars!)
>
> TIA
> Rick Staples
 
>F. As far as load points and info on such as that, I would defer your
>questions to Lee Harrison, the developer of the system. He has a small
>classified ad in MHMP under suspensions, be sure you told him we had
>discussed this on the net, he will be pleased this is happening and will
>be able to answer those questions fully. He can also furnish you with
>pics and install info, I think ytou will be suprised on how easy it is
>to install.

I called Leigh today about the system - he was very helpful. I will be
receiving his materials shortly. When I do I'll ask him if I can put it up
on my site for all to see.

>
>If you don't have a copy of the mag., call me tomorrow toll free at
>1-877-275-4462 and I'll give you his #.

His number is (703) 494-9914


Has anybody talked to Cinnabar or former GM designers about the 4-bag
system? If so, what's their response to the suspension changes?

Henry

Henry Davis Consulting, Inc / new product consulting
PO Box 1270 / product readiness reviews
Soquel, Ca 95073 / IP reviews
ph: (408) 462-5199 / full service marketing
fax: (408) 462-5198
http://www.henry-davis.com
 
>

> >The bottom line is, you really should investige the 4 air bag system if
> >you are going to be in the market for new air bags any time soon. It
> >costs a bit more than replacing the OEM bags, but with 2 bags costing
> >around $500.00, the cost of this tremendous performance modifcation is
> >not as far out of reach as it seems.
>
> Jim et al,
> I am intrigued by this system, especially with all the glowing
> testimonials. Where can I find out more info, especially: a. Does the 4-bag
> system use the stock suspension arms and shocks, and/or are they
> reinforced/replaced? b. Does it afford the full range of wheel travel and
> levelling that the stock system does? c. Does it provide as soft a ride as
> the stock system? d. Does it consume more air than the stock system (as seems
> to be implied in your post)? e. Does it leave at least as much clearance for
> oversize tires as does the stock suspension? f. Are suspension loads
> transferred to the frame approximately as in the stock system, and therefore
> is it able to withstand at least as much impact load (potholes) as the stock
> system?
> Most importantly, where can I find pictures, diagrams, and technical info
> on the 4-bag system? My position is all modifications are like UFOs: I have
> an open mind and am quite prepared to believe in them, but I need lots of hard
> facts before I can. (And LOTS of facts/details before investing all-too-rare
> dollars!)
>
> TIA
> Rick Staples

Rick,

I am pleased that you are interested and willing to investigate
further. First, let me try to answer the questions in your Email.

A. Yes, the system connects to the stock arms. It is a bolt up kit,
replacing the 4 nuts & bolts on the verticle surface of the "C" channel
and new nuts replacing the origional pin nuts.

B. As fa as travel, down motion is of course, the same as origional, the
up motion is reduced by only one inch.

C. Yes, the ride is very soft. Unlike stiffer shocks and sway bars that
have been used in the past to bandaid handling problems, this system
does not rely on opposing or impeeding swing arm travel. The suspension
is free to react to road conditions without the "push pull" motion of
the origional system. Standard shocks should do a good job of doing
what a shock is designed to do, obsorb small vibrations and average out
the performance of the suspension.

D. Yes, it is recomended to readjust the air pressure in the tank up to
130 PSI. The Thomas single cylinder compressor seemed to keep up with
the pressure requirements, but did heat up a bit while fiddling and
cycling the system repedidly. The V twin Hadley or the larger system
I'm working on would be a more dependable compliment to this system.

E. The system actually takes up less room betweenthe wheels and there
are no large, wide cones at the end that have problems clearing over
sized tires. I have a full restoration in house right now with Alcoas
and 235/75 tires. I am going to install a system soon and will be able
to give you a more accurate clearance # then.

F. As far as load points and info on such as that, I would defer your
questions to Lee Harrison, the developer of the system. He has a small
classified ad in MHMP under suspensions, be sure you told him we had
discussed this on the net, he will be pleased this is happening and will
be able to answer those questions fully. He can also furnish you with
pics and install info, I think ytou will be suprised on how easy it is
to install.

If you don't have a copy of the mag., call me tomorrow toll free at
1-877-275-4462 and I'll give you his #.

I am sure that if you look into this system, you will pick one up soon.

Let me know if you have any other questions.

Jim Bounds www.gmccoop.com
 
Wes Cauglan monitors this site and will surely answer.

>
>>F. As far as load points and info on such as that, I would defer your
>>questions to Lee Harrison, the developer of the system. He has a small
>>classified ad in MHMP under suspensions, be sure you told him we had
>>discussed this on the net, he will be pleased this is happening and will
>>be able to answer those questions fully. He can also furnish you with
>>pics and install info, I think ytou will be suprised on how easy it is
>>to install.
>
>I called Leigh today about the system - he was very helpful. I will be
>receiving his materials shortly. When I do I'll ask him if I can put it up
>on my site for all to see.
>
>>
>>If you don't have a copy of the mag., call me tomorrow toll free at
>>1-877-275-4462 and I'll give you his #.
>
>His number is (703) 494-9914
>
>
>Has anybody talked to Cinnabar or former GM designers about the 4-bag
>system? If so, what's their response to the suspension changes?
>
>Henry
>
>Henry Davis Consulting, Inc / new product consulting
>PO Box 1270 / product readiness reviews
>Soquel, Ca 95073 / IP reviews
>ph: (408) 462-5199 / full service marketing
>fax: (408) 462-5198
>http://www.henry-davis.com
>
>
 
I would love to see Wes participate in the discussions on this net and
hear his perspectives. So far, I haven't noticed such.

Thom, can you twist his arm some?????

Paul Bartz

> -----Original Message-----
> From: Thomas G. Warner [SMTP:warner]
> Sent: Wednesday, June 03, 1998 11:39 AM
> To: gmcmotorhome
> Subject: Re: GMC: 4 Air Bag rear suspension
>
> Wes Cauglan monitors this site and will surely answer.
>

>

>
> As far as load points and info on such as that, I would defer your
> questions to Lee Harrison, the developer of the system. He has a
> small classified ad in MHMP under suspensions, be sure you told him we
> had discussed this on the net, he will be pleased this is happening
> and will be able to answer those questions fully. He can also furnish
> you with pics and install info, I think ytou will be suprised on how
> easy it is to install.
>
> I called Leigh today about the system - he was very helpful. I will be
> receiving his materials shortly. When I do I'll ask him if I can put
> it up on my site for all to see.
>
>
> If you don't have a copy of the mag., call me tomorrow toll free at
> 1-877-275-4462 and I'll give you his #.
>
> His number is (703) 494-9914
>
>
> Has anybody talked to Cinnabar or former GM designers about the 4-bag
> system? If so, what's their response to the suspension changes?
>
> Henry
 
All I can tell you is that he has answered me by e-mail direct before on
several problems like the rotted floor I had.
will send him an e-mail and see if he will participate

>I would love to see Wes participate in the discussions on this net and
>hear his perspectives. So far, I haven't noticed such.
>
>Thom, can you twist his arm some?????
>
> Paul Bartz
>
>> -----Original Message-----
>> From: Thomas G. Warner [SMTP:warner]
>> Sent: Wednesday, June 03, 1998 11:39 AM
>> To: gmcmotorhome
>> Subject: Re: GMC: 4 Air Bag rear suspension
>>
>> Wes Cauglan monitors this site and will surely answer.
>>

>>

>>
>> As far as load points and info on such as that, I would defer your
>> questions to Lee Harrison, the developer of the system. He has a
>> small classified ad in MHMP under suspensions, be sure you told him we
>> had discussed this on the net, he will be pleased this is happening
>> and will be able to answer those questions fully. He can also furnish
>> you with pics and install info, I think ytou will be suprised on how
>> easy it is to install.
>>
>> I called Leigh today about the system - he was very helpful. I will be
>> receiving his materials shortly. When I do I'll ask him if I can put
>> it up on my site for all to see.
>>
>>
>> If you don't have a copy of the mag., call me tomorrow toll free at
>> 1-877-275-4462 and I'll give you his #.
>>
>> His number is (703) 494-9914
>>
>>
>> Has anybody talked to Cinnabar or former GM designers about the 4-bag
>> system? If so, what's their response to the suspension changes?
>>
>> Henry
>
>
 
>
> Wes Cauglan monitors this site and will surely answer.

I'd like to see him take part in these discussions, but as far as I
know, he's not subscribed(at least not under an email address that I
recognize). I guess he could be reading the archives.

Patrick
- --
Patrick Flowers
Mailto:patri63

The GMC Motorhome Page
http://www.gmcmotorhome.com
 
Patrick:

What's the customer count these days???

Paul

> -----Original Message-----
> From: Patrick Flowers [SMTP:patri63]
> Sent: Wednesday, June 03, 1998 7:24 PM
> To: gmcmotorhome
> Subject: Re: GMC: 4 Air Bag rear suspension
>

>
> Wes Cauglan monitors this site and will surely answer.
>
> I'd like to see him take part in these discussions, but as far as I
> know, he's not subscribed(at least not under an email address that I
> recognize). I guess he could be reading the archives.