Air suspension connection

[warrenivan]

Hi All.

We've got an '81 280. We've been going through it fixing, improving, etc.

It's got rear air suspension which is controlled by a little aux switch added by a previous owner to the dash. After fixing a bad ground for the air pump, they pressure up to about 90psi.

It's also got (manually filled) airbags in the front. They had been low since we bought it a few weeks ago. We filled them both up the other day (also to 90, though we weren't sure if this was the appropriate pressure).

Today, we noticed that the passenger air hose seems to have ruptured. The hose seems oddly thin/ flimsy, too.

So here are my questions:

If the hose burst, was the culprit likely an old hose, or was the PSI too high? And if it was (too high), do the hoses come in different thicknesses so that they burst instead of doing damage to the actual airbag?

Lastly. If the rear and front do indeed take the same PSI, can we connect them both to the same pump (instead of having to manually check and refill the front bags)?

I hope my question makes sense!

[Mike Leary]

Camping World has a hose set that goes up into the engine compartment with a pressure gauge to monitor both fronts. 60 psi is the norm. Given the age of your coach, I'd bet the springs are shot and the air bags are simply a crutch (which they were in the first place). The new springs for the P-30 chassis are much heavier and no bags are required. The rears are a whole 'nother can of worms. The "ideal" height for the rear bags are 8" to 10" measured from the top of the air bag support beam to the bottom of the main frame chassis rail. To achieve that, I run about 125 psi, which my original compressor did not supply. You can crawl under and inject air into the supply tank, but it's a pain. I've had more problems with that part of the coach than anything else, I finally had a spring shop rip all that crap out and replace it with a Haldex system.

haldex.com

[Smartstream]

Originally Posted by warrenivan

Hi All.

We've got an '81 280. We've been going through it fixing, improving, etc.

It's got rear air suspension which is controlled by a little aux switch added by a previous owner to the dash. After fixing a bad ground for the air pump, they pressure up to about 90psi.

It's also got (manually filled) airbags in the front. They had been low since we bought it a few weeks ago. We filled them both up the other day (also to 90, though we weren't sure if this was the appropriate pressure).

Today, we noticed that the passenger air hose seems to have ruptured. The hose seems oddly thin/ flimsy, too.

So here are my questions:

If the hose burst, was the culprit likely an old hose, or was the PSI too high? And if it was (too high), do the hoses come in different thicknesses so that they burst instead of doing damage to the actual airbag?

Lastly. If the rear and front do indeed take the same PSI, can we connect them both to the same pump (instead of having to manually check and refill the front bags)?

I hope my question makes sense!

According to Inland RV the front air bags are supposed to carry 55 psi. I think 90 psi is at or above the max rated pressure for the air bags. That may be why the hose failed. If you Goggle "air suspension" you will find many vendors that can supply that hose. I bought both bags and the install kit for less than $100 a few months ago. You could run the front bags from the compressor if you plumbed in a pressure regulator to reduce the pressure.

This outfit American Carrier Equip., Inc. - Series 800 for Truck Drive Axle made the rear suspension for the '82 280 and I believe it is the same as your '81. There is a valve that adjusts the ride height. It is located on the front of the crossmember at the top of the air bags. The valve varies the air pressure to maintain a constant height if and when the weight being carried changes. The correct height for the 82 and earlier coaches is 8 3/4" between upper and lower crossmembers, the actual height of the air bags themselves. The later coaches changed to 10". My coach normally loaded runs at about 72 psi in the bags.

As long as you are correcting things, that compressor draws a lot of amps when running. There should be a pressure switch that turns the pump on and off as needed. Many of us have installed a relay switch near the batteries to power the compressor directly from the batteries and just use the dash switch to operate the relay. This is better for the compressor and takes a load off the dash wiring.

Hope this answers your questions. Anything else comes to mind just ask.

Cheers, Dan

[warrenivan]

Thanks Dan and Mike. Those measurements will be very helpful.

We're experimenting with tying the front two airbags to the same line (so they can both be filled from one place) and replacing some of the tubing with harder stuff (we found a stash of new stuff from the previous owner). If that fails, we might look into other options - including connecting everything to the rear pump with a pressure regulator as you suggested.

Thanks again

[thenewkid64]

Originally Posted by warrenivan

Thanks Dan and Mike. Those measurements will be very helpful.

We're experimenting with tying the front two airbags to the same line (so they can both be filled from one place) and replacing some of the tubing with harder stuff (we found a stash of new stuff from the previous owner). If that fails, we might look into other options - including connecting everything to the rear pump with a pressure regulator as you suggested.

Thanks again

I would not recommend tying the two bags together. The inconvenience of 2 fill vales outweighs the fact that the bags will transfer pressure from one to another as you corner or maneuver. This will affect steering input and could cause a bag to become overinflated or under-inflated at the wrong time....

I just ran the schrader valve ends to a point behind the hood, 30 sec to check and top up max before each trip.