Home » Public Forums » GMCnet » [GMCnet] Rotating Bags
| [GMCnet] Rotating Bags [message #333836] |
Fri, 22 June 2018 08:26  |
Dean Hanson
Messages: 114
Registered: May 2018
Karma: 2
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I had the same OEM bags on my 23' 73 Glacier for 42 years and 220,000 miles
and never touched them. And never carried a cripple or spare. I'm
resurrecting a 1975 Avion now that had the OEM bags on it and had been
sitting in a field in Oregon in the desert for over 10 years. Pumped them up
and they held air nicely for about 6 months until I had Applied put on their
mono bag system. The PO had a new OEM bag on board but why push my luck. So
I have a new in the box GM bag for sale. If I could have found another
original bag, that's what I would have used.
Dean The Resourceful Norse Hanson
Fremont, Ca. 94536
(510) 657-9600
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| Re: [GMCnet] Rotating Bags [message #333841 is a reply to message #333836] |
Fri, 22 June 2018 08:42  |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
Karma: 10
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If people run their rear ride height at the correct level theoretically there is no reason to rotate the bags. If the level has been run too high then the bags start to hot dog. Rotating the bags occasionally does three things:
1. reverse the hot dog action and return the bag to normal.
2. Allow for easy inspection of the opposite side of the bag.
3. Assure the nuts and line will come loose easily should it be necessary to change a bag while on the road somewhere.
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
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| Re: [GMCnet] Rotating Bags [message #333853 is a reply to message #333836] |
Fri, 22 June 2018 12:28 |
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GMC2000
Messages: 193
Registered: March 2018
Location: Georgia
Karma: -3
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thats good to read.. most often only the bad news gets reported. I was starting to think a quad bag upgrade should be high priority and after one member mentioned to never get under a coach without a jack stand because if an air bag blew out, it goes to the ground so it now makes me slightly nervous to do so but that is good advice I think anyway.
most Ive looked at appear to have original air bags that look either very dry, dont hold air overnight, or look really dry rotted and cracked up. some so bad looking that I cant see how they hold air but they do. at least for the time being.
rotating fresh air bags that have no been hot dogged to prevent that seems like a good idea but I think rotating one that is hot dog shaped might not be a good idea. seems like that might create unnecessary stress? when they have taken on a hot dog shape, does that reduce their travel or effectiveness in some way?
Edit to add: Ive also been wondering if old ones that are still working good should be soaked with any type of treatments or not? I think probably not but perhaps something that makes them slightly softer and more flexible could be a good thing. there is stuff out there to soften tires that is used by some racers but it is against the rules in some orgs.
[Updated on: Fri, 22 June 2018 12:33] Report message to a moderator |
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| Re: [GMCnet] Rotating Bags [message #333868 is a reply to message #333836] |
Fri, 22 June 2018 18:02 |
JohnL455
Messages: 4447
Registered: October 2006
Location: Woodstock, IL
Karma: 12
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Though good in theory, rotating a bag that is way past design life may flex it in a new way that causes it to fail. Hard to say and prove. As far as protectants, it seems the original Armourall made vinyl smooth at first but then turned it rock hard and cracking. Again hard to prove as it may have hardened anyway but this was well prounounced. Some like 303 protectant, but the outer rubber coating does not do "work" other than covering the cord and protecting it. Air is held from inside. Stored indoors makes a difference. I am running new to me last of the Firestone bags and store indoors. That said I have had 2 Firestone 721 Steel radials on a 76 Pontiac explode in the last few years just sitting at like 30 PSI. I mean explode where the carcass and steel belts blew with shards. And these were replacement TPC tires from the national recall. Things don't last forever.
John Lebetski
Woodstock, IL
77 Eleganza II
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| Re: [GMCnet] Rotating Bags [message #333871 is a reply to message #333868] |
Fri, 22 June 2018 20:33 |
mrgmc3
Messages: 210
Registered: September 2013
Location: W Washington
Karma: 2
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JohnL455 wrote on Fri, 22 June 2018 18:02. That said I have had 2 Firestone 721 Steel radials on a 76 Pontiac explode in the last few years just sitting at like 30 PSI. I mean explode where the carcass and steel belts blew with shards. And these were replacement TPC tires from the national recall. Things don't last forever.
John, those tires mus be at least 30 years old! I don't think Firestone has made 721s since the 80s!
Chris Geils - Twin Cities / W Wa
1978 26' Kingsley w/ very few mods; PD9040, aux trans cooler, one repaint in stock colors, R134a, Al rad, Alcoas, 54k mi
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| Re: [GMCnet] Rotating Bags [message #333886 is a reply to message #333871] |
Sat, 23 June 2018 11:54 |
jimk
Messages: 6734
Registered: July 2006
Location: Belmont, CA
Karma: 9
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The main reason for the Hot Dog is wrong height at the rear.
The angle at the cone causes it to vector up.
On Fri, Jun 22, 2018 at 6:33 PM, Chris Geils via Gmclist <
gmclist@list.gmcnet.org> wrote:
> JohnL455 wrote on Fri, 22 June 2018 18:02
>> . That said I have had 2 Firestone 721 Steel radials on a 76 Pontiac
> explode in the last few years just sitting at like 30 PSI. I mean explode
>> where the carcass and steel belts blew with shards. And these were
> replacement TPC tires from the national recall. Things don't last forever.
>
>
> John, those tires mus be at least 30 years old! I don't think Firestone
> has made 721s since the 80s!
> --
> Chris Geils - Twin Cities / W Wa
> 1978 26' Kingsley w/ very few mods; Headers, PD9040, aux trans cooler,
> one repaint in stock colors, R134a, Al rad, Alcoas, 50k mi
>
> _______________________________________________
> GMCnet mailing list
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--
Jim Kanomata
Applied/GMC, Newark,CA
jimk@appliedairfilters.com
http://www.appliedgmc.com
1-800-752-7502
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Jim Kanomata
Applied/GMC
jimk@appliedairfilters.com
www.appliedgmc.com
1-800-752-7502
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| Re: [GMCnet] Rotating Bags [message #333888 is a reply to message #333886] |
Sat, 23 June 2018 12:59 |
James Hupy
Messages: 6806
Registered: May 2010
Karma: -62
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Also, understand this. The original airbags are 3 plies. The inner ply,
which holds the actual compressed air, is a rubber bladder, similar to an
inner tube. It has the filler valve vulcanized into it, and a machined flat
area inside the threaded nipple provides a flat seat for an "0" ring.
(FREQUENTLY THE LEAK SOURCE FOR THE BAG)
The second ply is fabric for support of the bladder.
The third ply, the only one you can see, is a very tough rubber,
similar looking to a tire sidewall. It is subject to Ultraviolet Radiation
from sunlight, and frequently shows some cracking which spreads "OHMYGOD,
THE SKY IS FALLING" type panic across the internet. It is a separate part
from the bladder that actually holds the air. The bladder has to fail in
order to lose air. NOT THE OUTER COVERING. Small visible cracks are USUALLY
no cause for alarm, but you should keep your eyes on them for changes. Most
leaks come from the internal "0" ring, or the fittings, hoses, and height
control valves. Bubble checking should reveal the source.
Jim Hupy ( presently located in the hospital hooked up to an infusion bag
of iron, as my hemoglobin count was low) Should be out of here later today.
Salem, Or
78 GMC ROYALE 403
On Jun 23, 2018 9:55 AM, "Jim Kanomata" wrote:
The main reason for the Hot Dog is wrong height at the rear.
The angle at the cone causes it to vector up.
On Fri, Jun 22, 2018 at 6:33 PM, Chris Geils via Gmclist <
gmclist@list.gmcnet.org> wrote:
> JohnL455 wrote on Fri, 22 June 2018 18:02
>> . That said I have had 2 Firestone 721 Steel radials on a 76 Pontiac
> explode in the last few years just sitting at like 30 PSI. I mean explode
>> where the carcass and steel belts blew with shards. And these were
> replacement TPC tires from the national recall. Things don't last forever.
>
>
> John, those tires mus be at least 30 years old! I don't think Firestone
> has made 721s since the 80s!
> --
> Chris Geils - Twin Cities / W Wa
> 1978 26' Kingsley w/ very few mods; Headers, PD9040, aux trans cooler,
> one repaint in stock colors, R134a, Al rad, Alcoas, 50k mi
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
--
Jim Kanomata
Applied/GMC, Newark,CA
jimk@appliedairfilters.com
http://www.appliedgmc.com
1-800-752-7502
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| Re: [GMCnet] Rotating Bags [message #333891 is a reply to message #333836] |
Sat, 23 June 2018 14:44 |
jhbridges
Messages: 8412
Registered: May 2011
Location: Braselton ga
Karma: -74
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Senior Member |
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While you're checkong the bags, when you get them working run the suspension all the way up and all the way down and make sure the height control valve lever stays clear of the lines. I managed to crimp and break both of mine. I now have loops out around the valve and back to the fitting. This problem occurs when you add a manifold and Schrader valve pointing upwards and use the same length air line to connect. This often puts the line in harm's way.
--johnny
Foolish Carriage, 76 26' Eleganza(?) with beaucoup mods and add - ons.
Braselton, Ga.
I forgive them all, save those who hurt the dogs. They must answer to me in hell
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