1995 Chevrolet P30 Air Bag Pressure

[bjarnold]

I had the air bags replaced on my 28ft Bounder and in the GM manual it shows the recommended pressure 60-100psi but Air Lift recommends 40-90. Should I go by the air bag manufacturers pressure or chassis manufactures pressure?

[72westy]

A recommendation of starting at 70-80psi for the front bags is too high. Your coach is 28ft and very likely has a front GAWR of 4880lb (same as mine 1994 P-30 28ft). The GM manual air bag pressures for a 5000 GAWR are 40psi min and 50psi max. Your min is likely 30-35psi but certainly not 40psi. look inside your closet it will have the weight GAWR ratings.

As for the measurements that were previously given they are NOT what the coach should be when adjusting. They are for determining the 'Degree set' for front alignment....

With respect to checking the ride height on the P series rig it must be measured between the upper control arm and the base of the rubber bump stop (iron to iron) ignore the rubber bumper. It also must be measured perpendicular to the upper control arm. This is with the RV level and air bag pressure at max pressure.

That measurement is then used to select the degree set for alignment. Some have said the measurement is between the top of the rubber bump stop and the upper control arm. This is incorrect. It is iron to iron. And the final measurement only has to do with the degree set for alignment and nothing else.

http://www.offroadtoybox.com/RV/P-Chassis-AlignmentProcess.pdf

[happycamper002]

dougrainer wrote:

You do NOT have to be an Engineer to KNOW what you have been taught and what you have learned over the years. People like you never let the facts get in your belief system. Curious, HOW MANY ENGINEERS WORK ON YOUR VEHICLES AND ON THINGS YOU NEED FIXED???????????????? Doug

You are throwing the baby with bath water.

As other posters have said: after replacing the airbag one needs to jack up the front end and adjust the air pressure to achieve the level.

Your mindset belongs to the league of technicians who told me that I needed a pair of shocks because the RV was leaning.

Seventeen years as a tech is a long time for someone not to learn much.

Don't get me wrong, there are good technicians out there.

Bottom line as I have said: to some extent, airbag pressure does help to level the rig.

Throw out the dirty water but don't throw away the baby.

[mfinnerty]

One thing I've noticed in this thread is that no one has mentioned that when air bags are replaced the front end alignment should be checked. I found out that my airbags were bad when I noticed severe wear on both front tires. After installing new airbags and determining the pressure I needed to maintain (70 psi) and getting new tires, I had the front end aligned.

[DougE]

I AM a mechanical engineer and I have always worked on my vehicles. I agree that I am rare though. A person's capabilities are a result of their education and experience. Vehicle experience can be gained by direct hands-on experience or by designing and testing. Some things are not correctly understood, however, without a background gained through advanced study. In the final analysis, though, I don't care whether you're a mechanic or an engineer. I just care whether your deduction is backed up by a logical basis.
Folks on this forum are supposed to be adults. Name calling is no substitute for facts.

[dougrainer]

happycamper002 wrote:
Big nonsense, CW replaced the blown airbag and corrected the problem.
How do you explain that.I still have the blown air bag to prove my point.

Try to make more sense in what you say to make yourself believable.

An Rv tech doesn't make an engineer.

You do NOT have to be an Engineer to KNOW what you have been taught and what you have learned over the years. People like you never let the facts get in your belief system. Curious, HOW MANY ENGINEERS WORK ON YOUR VEHICLES AND ON THINGS YOU NEED FIXED???????????????? Doug

[enblethen]

Yes, after install load needs to be taken off the air bag so it straightens out. Only takes 30-40 pounds.

[bjarnold]

I heard that you are supposed to also jack up the front axle in the middle when you inflate them but I don't know if it's true or not

[Clay_L]

I had a 96 motor home on a 95 P30/32 chassis. The vehicle owners manual described how to set the pressure in the airbags. In case you don't have the manual this is what mine said:

The owner’s manual gives the following ranges:

4,300 LB front suspensions = 10 psi to 50 psi
5,000 LB front suspensions = 40 psi to 50 psi
5,300 LB front suspensions = 50 psi to 80 psi
5,500 LB front suspensions = 60 psi to 100 psi

For the proper adjustment it says to inflate the air bags to the maximum pressure for your vehicle, load the motor home, park on a level surface and then reduce the air pressure as needed to level the motor home but don’t reduce it below the minimum.

I have seen other schemes for adjusting the pressure per ride quality, but the 1995 Chevrolet Forward Control Chassis owner’s manual said to do it as shown above.

I don't know if it's accurate or not but other posts have said the pressure in the bags affects the alignment and you should have it checked when you get the pressure set. The manual did not mention that however.

[enblethen]

The distance from the rubber bump stop on the lower control arm to where it would make contact on the upper control arm should be between 1.75 and 2.5 inches.

[bjarnold]

The shop that did the air bags only works on diesel trucks and farm equipment so they have a pretty good knowledge of what they are doing. They said everything looked fine and they replaced the sway bar bushings as well. They also pulled out the coil springs to replace the air bags which I was not expecting. The ride height on the bumpers is approx. 2". I should have measured the actual "lift" from the new air bags before and after but I can tell you that before I was able to reach above the front side windows to apply wax to the coach now I can only reach half way up the side window's. So probably 6" or so

[turbojimmy]

Gjac wrote:
What does you ride height measure from side to side? You should have at least 1.75 ins.

1.75" from where? Just curious because I often wonder about my ride height. Being able to control the rear height with the Jet Ride system has a pretty big impact on overall handling. In my "auto" setting I think it's actually sitting a little low.

[enblethen]

I had about a 2 inch piece broken off the bottom of the right front coil spring. Found it while shop was installing Henderson Super Coils.
The fourth character in the VIN number indicates gross vehicle weight.
G= 8,001-9,000
H= 9,000 10,000
J= 10,000- 14,000
K= 14,0001-16,000
seventh character indicates style of chassis. This seems to very!
2 is forward control
7 is motorhome

[Gjac]

bjarnold wrote:
Right now I have them at 80psi. After the old bags were replaced the front end did come up noticeably. Before it looked like a hod rod with the nose to the ground. Now it is sitting just about level. I put a level inside the freezer and it's actually sitting a little nose high

What does you ride height measure from side to side? You should have at least 1.75 ins. On a light 28 ft MH your springs may be fine but depending on age and miles driven the springs both front and rear do wear out and the bags alone may not be able to provide the right ride height. As Bud posted many of us had to go with a heavier duty coil spring from Henderson to lift the upper A arm off of the lower bumper stop to get the proper ride height. If it now rides nose up check the ride height in the rear your rear springs may be sagging some.

[harold1946]

happycamper002 wrote:
Big nonsense, CW replaced the blown airbag and corrected the problem.
How do you explain that.I still have the blown air bag to prove my point.

Try to make more sense in what you say to make yourself believable.

An Rv tech doesn't make an engineer.

Doug is absolutely correct. The rear suspension of your RV has been modified by someone.
Neither GM nor Workhorse ever used air suspension, (or air assist) on the rear suspension of their chassis.

Get all the facts right and you will not be giving everyone WRONG information, and making yourself look rather inept.