Home » Public Forums » GMCnet » [GMCnet] GMCnet Quad Bags
| [GMCnet] GMCnet Quad Bags [message #370413] |
Mon, 29 August 2022 09:58  |
Chris McBride
Messages: 35
Registered: June 2021
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My relatively new looking air bag blew while parked at my TZE service center. The owner of the shop asked me to consider the Quad Bag conversion. Is there any down side to converting the coaches original system and are there better kits out there?Thank you,Eric
Eric Roell, Aurora, Ontario76 Glenbrook "Safari" 76,000 miles,Alcoa, Continental Kit, Fender Flares, Stainless Exhaust, Macerator, Ragusa Step
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| Re: [GMCnet] GMCnet Quad Bags [message #370414 is a reply to message #370413] |
Mon, 29 August 2022 10:14  |
boybach
Messages: 566
Registered: December 2020
Location: Vancouver Island
Karma: 4
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In your position I'd buy a pair of new bags and be done with it. Keep the non-blown one for a spare.
While fitting the quad system is an option, (as is the sully system) the quad bag conversion can lead to the discovery of other worn components that may need attention and may prolong the work and expense, and the quad bag system is already pretty pricey especially if you're getting a shop to do the work.
Just what I would do - YMMV
Larry
Larry - Victoria BC -
1977 ex-Palm Beach "Ol' Leaky" 40,000 miles, PO said everything working but forgot the word NOT. Atwood helium fridge, water heater & furnace. SS exhaust system, Onan, Iota Converter, R134A, New fuel lines & heat exchange hoses
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| Re: [GMCnet] GMCnet Quad Bags [message #370415 is a reply to message #370413] |
Mon, 29 August 2022 10:34 |
Larry
Messages: 2875
Registered: January 2004
Location: Menomonie, WI
Karma: 10
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Here are copy/paste of several responses I did on this topic a year ago on the other forum. Hope this helps.
I've had three different systems on my coach in the last 18 yrs. The OEM system when I bought it, I drove for about 7yrs. Worked fine running at about 80lbs. But they were original from 1978 and looking pretty bad. So I bought the Sully system and had it waiting at home for me to install. On the way home from Florida that winter, we stopped at our daughter's home in Minnesota. I leveled up, and 20 minutes later, with a HUGE BANG, the passenger side bag blew out and put me on the ground. I was carrying a spare (almost worse than the one that blew) so I installed it and drove the 70mi home. Installed the Sully system (easy install) and found ride height at 45lbs. I can't say I noticed a nickels worth of difference in ride between the Sully system and OEM. But the lower pressures put less strain on every thing in the punematic system. It aired up quick and had almost the same range of motion. I liked it, and was a lot less money than replacing with the OEM bags. In addition, my decision to run with the Sully. system was influenced by rumors of the failure of the off shore OEM bags coupled with replacement bags of the Sully system could be found at most any truck stop. Finally, the bags used in the Sully system are designed for use on 18 wheelers and on our coaches running at 45 to 60 lbs are WAY over rated for the 8000lbs we are carrying on our coaches. Well then sfter running those for 7yrs, I installed the Lenzi disc brake system on the rear of our coach. Problem then is that the low pressure of the Sully system coupled with the pole vaulting effect of heavy braking allowed the rear axle to lock up way to easy flat spotting tires. So, I bought a used Harrison system that I got cheap (Harrison system is the original 4 bag) and installed that. A comparatively difficult install with typical pressures running around 100psi. Again, I can't feel a nickels worth of difference in the ride, but because of the way the Harrison system works, the locking up of the rear axle no longer happens. I've had to adjust the pressure regulator up to it's max at 150lbs in order to get it to turn on for leveling when I need to jack the rear up for site leveling. I wish I could find a larger replacement bag for the Harrison bag to bring the pressures down. There is one bag that will fit, but only slightly larger. Anyway, that's my story, hope it helps someone making decisions on system swaps.
BTW, I experimented with some "Airbagit" air springs that had aluminum mounting plate. Seemed like the perfect solution. Bigger bag, same mount bolting and air placement. Got me down under 90lbs, but that aluminum under the strain of the minor twist it has to endure when inflating to 140ls on a full "up" was enough to crack the aluminum plates and thus leak most of the air over night. Took exchanging several cracked plates with "Airbagit" before they relented that the design was for a streight push on the plate rather than the slight twist. A learning experience I don't want to endure again. There are two bags out there that appear to work just fine. The original was a Firestone W01-358-7659 at 7.44" diameter. "Torque" makes an identical bag #7659 at half the price. Firestone makes a W21-760-0335 at 7.52" diameter. Slightly bigger in diameter so slightly lower pressures, same mounting and air, at Firestone prices. HTH
I know some are not in favor of some of the aftermarket airbag systems. The original single bag system back in the 70's was way ahead of its time, and even now, certainly a good option for those who want to keep it original. But consider these points.
For the quad bag system (4bag), the bags are readily available from several manufactures and are 1/4 to 1/2 the price of the OEM replacement bags. The bags used in these systems are brought over from systems designed for use on trucks and might be considered way over rated when used on the GMC. Most are readily available at Amazon and other online sources and can be found at many truck stops and truck repair facilities. These bags are designed for long term over the road use and will probably out live you, so considering longevity and availability no need carry spare. The OEM Bags are only available from a limited number of sources, and because of the low production numbers, are quite expensive.
In addition, the quad and 4bag systems, by design, have a solid mounting plate between the bags. The nature of this setup allows both bags to be inflated equally to...say... 110psi. When under hard braking, while the single bag systems may unload the rear tire (sometimes called "pole vaulting") leading to that tire loosing traction (skidding), the quad/4bag systems have a single bag for each arm and keep a full 110PSI of down force on both bogie arms, with no pole vaulting effect and little or no transfer of weight to the front arm, thus significantly reducing rear wheel loss of traction. This becomes significant when going to the heavy duty disc systems that can be installed on the front axle (of the rear).
It could be said that the solid plate between the two bags does not allow for a smooth ride over bumps like speed bumps. I have noticed no difference in coach handling between the original or Sully systems as compared to the 4bag over speed bumps. Felt the same to me, and I've tested this at speeds exceeding 30mph. A smooth ride back there.
Or, look at the whole thread with other responses here:
https://www.gmcmotorhome.org/threads/quad-airbag-suggestions.1180/
Larry 
78 Royale w/500 Caddy
Menomonie, WI.
[Updated on: Mon, 29 August 2022 10:42] Report message to a moderator |
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| [GMCnet] Re: GMCnet Quad Bags [message #370416 is a reply to message #370413] |
Mon, 29 August 2022 11:22 |
lcoldren
Messages: 28
Registered: March 2004
Karma: 0
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Eric, I have been running the Quad bag system sold by gmcrvparts.com since 2008 and am very happy with them. Give Jim Kanomata a call 800-725-7502. I find the Quad Bags gives a more stable ride than the single bag system.
Larry Coldren
1974 Canyon Lands
Ft. Collins, CO
________________________________
From: Eric Roell
Sent: Monday, August 29, 2022 08:58 AM
To: Emery Stora via Gmclist
Subject: [GMCnet] GMCnet Quad Bags
My relatively new looking air bag blew while parked at my TZE service center. The owner of the shop asked me to consider the Quad Bag conversion. Is there any down side to converting the coaches original system and are there better kits out there?Thank you,Eric
Eric Roell, Aurora, Ontario76 Glenbrook "Safari" 76,000 miles,Alcoa, Continental Kit, Fender Flares, Stainless Exhaust, Macerator, Ragusa Step
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| Re: [GMCnet] GMCnet Quad Bags [message #370417 is a reply to message #370413] |
Mon, 29 August 2022 12:42 |
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RF_Burns
Messages: 2277
Registered: June 2008
Location: S. Ontario, Canada
Karma: 3
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The OEM and other single bag systems transfers road shock from one one rear tire to the opposite tire giving a smoother ride. It also by design balances the rear load between the two wheels on each side.
The Quadra bag does not transfer the road shock of a bump to the opposite wheel... it transfers the shock directly to the bogie mount and to the frame. Look at any tandem axle, they use a pivot point between the two springs to balance the load between the wheels and to transfer shock. The quadra bag does none of this.
My current airbags are a single bag from Applied, I believe were called "Silvertone" at the time (~2010). I'm not sure if they are a current model, but I would not recommend them because if they deflate the internal opening for the inflation air gets covered by the opposite side of the airbag. This prevents you from re-inflating the airbag until you lift the coach a bit using a jack, then you can re-inflate the airbag.
When I replace them, I will go with Cinnabar reproduction OEM or the Alex Ferrara single bag.
Bruce Hislop
ON Canada
77PB, 455 Dick P. rebuilt, DynamicEFI EBL EFI & ESC.
1 ton front end
http://www.gmcmhphotos.com/photos/showphoto.php?photo=29001
My Staff says I never listen to them, or something like that
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| [GMCnet] Re: GMCnet Quad Bags [message #370418 is a reply to message #370413] |
Mon, 29 August 2022 12:39 |
Keith V
Messages: 2337
Registered: March 2008
Location: Mounds View,MN
Karma: 0
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Cost and ride quality.
Upsides are you can run with 1 bad bag per side, or a bad tire.
Lots of choices for single bag replacements
________________________________
From: Eric Roell
Sent: Monday, August 29, 2022 9:58 AM
To: Emery Stora via Gmclist
Subject: [GMCnet] GMCnet Quad Bags
My relatively new looking air bag blew while parked at my TZE service center. The owner of the shop asked me to consider the Quad Bag conversion. Is there any down side to converting the coaches original system and are there better kits out there?Thank you,Eric
Eric Roell, Aurora, Ontario76 Glenbrook "Safari" 76,000 miles,Alcoa, Continental Kit, Fender Flares, Stainless Exhaust, Macerator, Ragusa Step
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Keith Vasilakes
Mounds View. MN
75 ex Royale GMC
ask me about MicroLevel
Cell, 763-732-3419
My427v8@hotmail.com
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| [GMCnet] Re: GMCnet Quad Bags [message #370419 is a reply to message #370413] |
Mon, 29 August 2022 15:12 |
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ljdavick
Messages: 3548
Registered: March 2007
Location: Fremont, CA
Karma: -3
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Eric,
The quadrabag replacement is a fine choice however there are cheaper alternatives. I bought the 4-bag system that has been discontinued as the mount was not substantial enough to handle the torquing of the bogies when turning. I’m keeping my fingers crossed that the true trackers will keep them in line.
Larry Davick
A Mystery Machine
1976(ish) Palm Beach
Fremont, Ca.
> On Aug 29, 2022, at 7:58 AM, Eric Roell wrote:
>
> My relatively new looking air bag blew while parked at my TZE service center. The owner of the shop asked me to consider the Quad Bag conversion. Is there any down side to converting the coaches original system and are there better kits out there?Thank you,Eric
>
> Eric Roell, Aurora, Ontario76 Glenbrook "Safari" 76,000 miles,Alcoa, Continental Kit, Fender Flares, Stainless Exhaust, Macerator, Ragusa Step
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
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Larry Davick
A Mystery Machine
1976(ish) Palm Beach
Fremont, Ca
Howell EFI + EBL + Electronic Dizzy
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| Re: [GMCnet] GMCnet Quad Bags [message #370420 is a reply to message #370417] |
Mon, 29 August 2022 16:34 |
dsmithy
Messages: 210
Registered: July 2012
Location: Lincoln Nebraska
Karma: 0
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I grant Bruce's logic on quad bag structure but I don't feel it with the ride I get. Smooth as silk on any surface including crossing railroad tracks. I had an OEM bag blow at speed and called JimK from the side of the road to order his quad bag system. Practically no research into different approaches, but we have been very happy with the result. If the road is straight-ish sleeping in the back at 65-70 is no problem and it tracks well, even with a little wear on the bogie pins. Expensive and sort of a PIA to install but we only felt that pain once and we've been delighted ever since. YMMV, but we are happy with our choice.
Douglas & Virginia Smith,
dsmithy18 at gmail,
Lincoln Nebraska,
’73 “Sequoia” since ‘95: "Wanabizo";
Quadrabag/6 wheel disks/3:70 final/Paterson QuadraJet/Thorley’s/Alloy wheels/Sundry other
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| Re: [GMCnet] GMCnet Quad Bags [message #370421 is a reply to message #370413] |
Mon, 29 August 2022 17:23 |
Carl S.
Messages: 4186
Registered: January 2009
Location: Tucson, AZ.
Karma: 13
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I have the Quadrabag system on my coach I bought the system second hand from another GMGer who got them from Applied. He bought a nicer coach and changed plans on the one he bought the quads for and sold them to me at a good discount. I would have eventually done the conversion even at full price. I just (last week) changed out the 12 year old bags for a new set of Firestones from Applied due to the outside rubber separating. I just didn't trust them and would MUCH rather change them out at home than along the road somewhere,
I think they provide a slightly firmer, more controlled ride, but that is purely subjective and frankly, I didn't notice much difference in the ride. I like the redundancy that is built into the system which allows the isolation of any of the four bags in case of a blown bag or an air line problem. They also allow full suspension travel up and down for campsite leveling, which I don't believe is the case with the other single bag systems (other than OEM)
Carl Stouffer
'75 ex Palm Beach
Tucson, AZ.
Chuck Aulgur Reaction Arm Disc Brakes, Quadrabags, 3.70 LSD final drive, Lenzi knuckles/hubs, Dodge Truck 16" X 8" front wheels, Rear American Eagles, Solar battery charging. GMCSJ and GMCMI member
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| Re: [GMCnet] GMCnet Quad Bags [message #370424 is a reply to message #370413] |
Mon, 29 August 2022 20:01 |
lqqkatjon
Messages: 2324
Registered: October 2010
Location: St. Cloud, MN
Karma: 5
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Senior Member |
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What else does your coach need?
There are basically 4 available systems. Sully, daytona. Stock/oem or quadbag.
The sully, the daytona, and the oem are all close in price and are single bag systems you can install quickly and easily. Maybe $500 a side.
Quadbags are 2 to 3 times as much money and complexity.
If you have everything else on your coach fixed and working, look at quadbags and do research what you are getting into. If there is something else that needs that extra $1000-$1500. Fix that and buy one of the single bag systems and get other systems fixed up and working right.
Jon Roche
75 palm beach
EBL EFI, manny headers, Micro Level, rebuilt most of coach now.
St. Cloud, MN
http://lqqkatjon.blogspot.com/
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| Re: [GMCnet] GMCnet Quad Bags [message #370425 is a reply to message #370413] |
Mon, 29 August 2022 20:03 |
Tom Katzenberger
Messages: 399
Registered: June 2019
Location: Kingsville, MD
Karma: 4
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Senior Member |
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Bruce,
Keep us informed as I also have my antennas up for Branscombe's new Electronic Parking Brake.
Take care,
Tom K.
Tom & Oki Katzenberger,
Kingsville, Maryland,
1977 23' Birchaven, 455 C.I.D., Micro Level, Howell EBL-EFI Spark Control, Macerator, York Air Compressor, 6 Wheel Disc, Quadra Bag, Onan W/Bovee Ignition
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| Re: [GMCnet] GMCnet Quad Bags [message #370427 is a reply to message #370413] |
Tue, 30 August 2022 08:30 |
Tom Katzenberger
Messages: 399
Registered: June 2019
Location: Kingsville, MD
Karma: 4
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Senior Member |
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Larry,
I really like the 2 stage MC. Thank you for the tip. So far so good.
Are you still feeling success with it, as I am sure you have traveled many more mile then I?
Tom K.
Tom & Oki Katzenberger,
Kingsville, Maryland,
1977 23' Birchaven, 455 C.I.D., Micro Level, Howell EBL-EFI Spark Control, Macerator, York Air Compressor, 6 Wheel Disc, Quadra Bag, Onan W/Bovee Ignition
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| Re: [GMCnet] GMCnet Quad Bags [message #370429 is a reply to message #370413] |
Tue, 30 August 2022 09:46 |
Tom Katzenberger
Messages: 399
Registered: June 2019
Location: Kingsville, MD
Karma: 4
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Senior Member |
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Larry,
I agree absolutely. I believe we (the community) will come up with a hack or work around for the small reservoir.
Take care,
Tom K.
Tom & Oki Katzenberger,
Kingsville, Maryland,
1977 23' Birchaven, 455 C.I.D., Micro Level, Howell EBL-EFI Spark Control, Macerator, York Air Compressor, 6 Wheel Disc, Quadra Bag, Onan W/Bovee Ignition
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| Re: [GMCnet] GMCnet Quad Bags [message #370430 is a reply to message #370429] |
Tue, 30 August 2022 10:14 |
rjw
Messages: 697
Registered: September 2005
Karma: 4
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Senior Member |
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Count me in as a very satisfied user of Dave's mid-brake disk system. I also have 80MM calipers in the front and still have the rear drum brakes with slave cylinders increased in size from OEM. I also have his sensitized brake booster with a master cylinder he machined and matched to fit the booster. Plus I have his reserve vacuum system. Added all that to Applied/Coop's quad-bag.
Overall I am extremely happy with the way my coach now stops. It stops just like my Ford Escape. It sure didn't do that before. My coach stops way better than it looks.
Now I am shopping for a parking brake. I have Branscombe's earlier parking brake half installed. I was unable to complete the installation because of clearance issues caused by the vacuum operated entrance step the PO installed 30 years ago. I am very interested in the Lenzi approach to parking brakes should he finally get it perfected or Branscombe's new parking brake. Or I will figure out how to install the one I have half installed.
Richard
76 Palm Beach
SE Michigan
www.PalmBeachGMC.com
Roller Cam 455, TBI+EBL, 3.42 FD, 4 Bag, Macerator, Lenzi (brakes, vacuum system, front end stuff), Manny Tranny, vacuum step, Tankless + OEM water heaters.
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