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[GMCnet] Air Bag Pressure/ride height [message #259708]

Fri, 22 August 2014 01:02

Sergio Mora
Messages: 15
Registered: May 2014

Karma: 0

Junior Member

What is the correct air pressure on the air bags and corresponding ride height?(for the rear)

The PO installed shut off valves to isolate the bags from leaking down and I have yet to test the compressor(s). I know one works cause I heard it on the other day. I believe the second compressor is not working. I am a new owner and haven't had the courage to mess with the leveling system in fear that I will break something. (I level it at sites with wood-).

Currently there is 80PSI in each bag . I added 5 psi today to see what it would do to the height-it came right up about an inch or so. I ave not driven it since but before I added the 5psi it drove real nice and smooth, maybe a little bouncy in the rear (soft) when hitting dips.

I remember seeing somewhere on the discussions where to measure the ride height and 11.5 inches comes to mind as the measurement but I will take any and all advice as to what I should be running in the bags until I sort out the electro level system in the coach.

On a side note...I was driving on a call today and saw a blue coach with Arizona plates, I couldn't stop because I was on my way to an emergency. After the call I went looking for the coach and found the coach at Wal-mart.

Had a real nice conversation with the owner.

This is a great community....

Thanks again for the help

Sergio Mora
National City Fire Department
Battalion Chief- Operations
smora@nationalcityca.gov
619 336-4555 office
619 336-4566 sta.34
619 250-1724 mobile

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Re: [GMCnet] Air Bag Pressure/ride height [message #259711 is a reply to message #259708]

Fri, 22 August 2014 01:30

Ken Burton

Messages: 10030
Registered: January 2004
Location: Hebron, Indiana

Karma: 10

Senior Member

There is no set pressure for the airbags. The air pressure varies depending on the weight of and the weight loaded inside of the coach. It is a dynamic system that adjusts as you load up and drive the coach.

That said with the bags shutoff, you are going to have to determine what pressures are correct for your coach. The ride rear height number is in the maintenance manual. What I did was cut a couple of 2x4's to match the clearance beneath the frame rather than the distance to the hole in the frame. I do not have the sizes available here because my coach in not at home.

If you will call Jim K. He has those sizes.

Some people will give you a measurement to the inside top of the fender well. That number is not accurate because these coaches vary depending on the condition and thickness of the body isolators. Do it correctly with a pair of cutoff 2x4's and the measure the height to the bottom of the fender wells. After that you can measure to the fendr well line and you will have accurate numbers to match your coach.

Someday get your automatic leveling system working again. We have found that 1/4" difference in rear height makes a 125 pound shift in applied weight to the front wheels. Than means that 1" difference on the rear equals 500 pounds of weight shift on the front.

Edit: Note: It took 147 seconds for the system to respond to this posting with no SQL error. So there is still a response time problem although the read (not posting) response time is acceptable.

Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana

[Updated on: Fri, 22 August 2014 01:35]

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Re: [GMCnet] Air Bag Pressure/ride height [message #259720 is a reply to message #259708]

Fri, 22 August 2014 05:03

Mr ERFisher

Messages: 7117
Registered: August 2005

Karma: 2

Senior Member

read here
http://gmcmotorhome.info/list.html#Rear
erf

On Thu, Aug 21, 2014 at 11:02 PM, Sergio Mora
wrote:

> What is the correct air pressure on the air bags and corresponding ride
> height?(for the rear)
>
> The PO installed shut off valves to isolate the bags from leaking down and
> I have yet to test the compressor(s). I know one works cause I heard it on
> the other day. I believe the second compressor is not working. I am a new
> owner and haven't had the courage to mess with the leveling system in fear
> that I will break something. (I level it at sites with wood-).
>
> Currently there is 80PSI in each bag . I added 5 psi today to see what it
> would do to the height-it came right up about an inch or so. I ave not
> driven it since but before I added the 5psi it drove real nice and smooth,
> maybe a little bouncy in the rear (soft) when hitting dips.
>
> I remember seeing somewhere on the discussions where to measure the ride
> height and 11.5 inches comes to mind as the measurement but I will take any
> and all advice as to what I should be running in the bags until I sort out
> the electro level system in the coach.
>
> On a side note...I was driving on a call today and saw a blue coach with
> Arizona plates, I couldn't stop because I was on my way to an emergency.
> After the call I went looking for the coach and found the coach at Wal-mart.
>
> Had a real nice conversation with the owner.
>
> This is a great community....
>
>
> Thanks again for the help
>
> Sergio Mora
> National City Fire Department
> Battalion Chief- Operations
> smora@nationalcityca.gov
> 619 336-4555 office
> 619 336-4566 sta.34
> 619 250-1724 mobile
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
>

--
Gene Fisher -- 74-23,77PB/ore/ca
“Give a man a fish; you have fed him for today --- give him a URL and
-------
http://gmcmotorhome.info/
Alternator Protection Cable
http://gmcmotorhome.info/APC.html
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Re: [GMCnet] Air Bag Pressure/ride height [message #259737 is a reply to message #259708]

Fri, 22 August 2014 08:02

USAussie

Messages: 15912
Registered: July 2007
Location: Sydney, Australia

Karma: 6

Senior Member

Sergio,

I don't know what year coach you have but click on this link and download the Maintenance Manual X-7525:

http://www.bdub.net/factory-manuals.html

Go to: Section 4 Rear Suspension / Page 4-34 / Figure 70 - Checking Vehicle Ride height

Here's a photo of what the slot on the passenger side of the frame looks like:

http://www.gmcmhphotos.com/photos/aa-miscellaneous-photos/p40040-rear-height-adjustment.html

Unfortunately the one on the driver side is obscured by the Onan which is why the text under the photo notes to cut two 4 x 4's to 8
1/6 in and use them to measure the height.

Moving the lever on the ride height valve can be a bugger so you might want to consider buying a set of adjustable links from:

Ken Henderson: http://www.gmcwipersetc.com/

Or

Dave Lenzi: http://www.bdub.net/lenzi/index.html

You may have to adjust the front ride height as well so to save time here's how to do that:

See Maintenance Manual X- 7525 / Section 3 - Front Suspension / Page 3A-20 / Ride Height Adjustment

Here's a photo of the front ride height adjustment slot photo:

http://www.gmcmhphotos.com/photos/aa-miscellaneous-photos/p40039-front-height-adjustmen.html

DO NOT TRY AND ADJUST THE FRONT RIDE HEIGHT WITHOUT THE TOOL. Some people have been able to but there is a good chance you will
strip the bolts.

Here's a photo of the special tool:

http://www.gmcmhphotos.com/photos/torsion-bar-tool/p29589-torsion-bar-porkchoptool.html

They can be purchased on eBay too:

http://www.ebay.com/itm/GM-Chevy-Ford-Dodge-Torsion-Bar-Unloading-Tool-Key-/260533262597

After making the adjustments you will need to go for a test ride to make sure it is correct, ESPECIALLY on the front suspension!

Regards,
Rob M.
The Pedantic Mechanic
USAussie - Downunder
USA '75 Avion - Double Trouble TZE365V100426
AUS '75 Avion - The Blue Streak TZE365V100428

-----Original Message-----
From: Sergio Mora

What is the correct air pressure on the air bags and corresponding ride height?(for the rear)

The PO installed shut off valves to isolate the bags from leaking down and I have yet to test the compressor(s). I know one works
cause I heard it on the other day. I believe the second compressor is not working. I am a new owner and haven't had the courage to
mess with the leveling system in fear that I will break something. (I level it at sites with wood-).

Currently there is 80PSI in each bag . I added 5 psi today to see what it would do to the height-it came right up about an inch or
so. I ave not driven it since but before I added the 5psi it drove real nice and smooth, maybe a little bouncy in the rear (soft)
when hitting dips.

I remember seeing somewhere on the discussions where to measure the ride height and 11.5 inches comes to mind as the measurement but
I will take any and all advice as to what I should be running in the bags until I sort out the electro level system in the coach.

On a side note...I was driving on a call today and saw a blue coach with Arizona plates, I couldn't stop because I was on my way to
an emergency. After the call I went looking for the coach and found the coach at Wal-mart.

Had a real nice conversation with the owner.

This is a great community....

Thanks again for the help

Sergio

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GMCnet mailing list
Unsubscribe or Change List Options:
http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist

Regards, Rob M. (USAussie) The Pedantic Mechanic Sydney, Australia '75 Avion - AUS - The Blue Streak TZE365V100428 '75 Avion - USA - Double Trouble TZE365V100426

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Re: [GMCnet] Air Bag Pressure/ride height [message #259757 is a reply to message #259711]

Fri, 22 August 2014 11:19

rjw

Messages: 697
Registered: September 2005

Karma: 4

Senior Member

Ken Burton wrote on Fri, 22 August 2014 02:30

There is no set pressure for the airbags. The air pressure varies depending on the weight of and the weight loaded inside of the coach. It is a dynamic system that adjusts as you load up and drive the coach.

Someday get your automatic leveling system working again. We have found that 1/4" difference in rear height makes a 125 pound shift in applied weight to the front wheels. Than means that 1" difference on the rear equals 500 pounds of weight shift on the front.

Ken,
You are right about the ride height. When I helped you and Chuck Boyd set my ride height back in the Spring, I assumed the effect would be trivial. I was wrong, it made a noticeable difference in handling. I don't remember how far I was off, maybe only 1/2" or 250 lbs side to side as measured by your truck scales. That seemed to me like a minor amount to be off, but when you guys corrected it, what an improvement it made.

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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Re: [GMCnet] Air Bag Pressure/ride height [message #259759 is a reply to message #259757]

Fri, 22 August 2014 11:26

Keith V

Messages: 2337
Registered: March 2008
Location: Mounds View,MN

Karma: 0

Senior Member

Also understand the suspension is very sticky.
Adjust, jump on the bumper, check, adjust again, then drive it around the block
It is very hard to get round the stickiness and hysteresis on these things.

And you need to find a very level pad to check the height on...

Keith Vasilakes
Mounds View. MN
75 ex Royale GMC
ask me about MicroLevel
Cell, 763-732-3419
My427v8@hotmail.com

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