air bag pressure

[junkman42]

Help, can someone tell Me how much air pressure to run on My bags on a mci 7.  Front is at 70 rear axle is at 70 and tag is at 45.  The bus always looks like it is going down hill.  Any suggestions would be appreciated.

[Nick Badame Refrig/ACC]

Hi junkman42,

Welcome!

I moved your question from the Calander to the main board for better responces.

Nick-

[JackConrad]

Help, can someone tell Me how much air pressure to run on My bags on a mci 7.  Front is at 70 rear axle is at 70 and tag is at 45.  The bus always looks like it is going down hill.  Any suggestions would be appreciated.

    First, a question, Are still running the OEM leveling valves?  Our system uses the OEM leveling valves when the engine in running and a manuallly controlled system when we are parked. When driving, our front and drive axle bags are usually around 55-60, tags are 35. I don't have my service manual handy, but I believe the factory setting is 3 9/16" between the axle and the axle bumper. CHECK THIS BEFORE MAKING ANY CHANGES, I MAY BE WRONG! The tag axle pressure regulator is supposed to set at 35 PSI.  If you have 45 in your tags, this may be lifting the back of the bus.  Have you had your bus weighed per axle? Tag is supposed to carry a maximum of 6000#.
    Of course, we all know we get better mileage running downhill. Hope this helps, Jack

[Stan]

Jack is correct: Bag pressure is a function of weight carried and is determined by ride height. On a level floor. adjust the leveling valve links to set the ride height, by the book. Once set, everything is automatic.

[TomC]

Without specific measurements, the air suspension should be adjusted to about 55-60% of the ride height.  If you have a total of 7 inches of travel, should set it at 4 inches.  On my bus, I have mine set 1 inch below top travel because of the low ground clearance I have on my transit.  So far no problems.  And going against what everyone would think, if you want a better ride, you want the air suspension in the highest position possible.  The higher the air bag , the more air you'll have in the bag and the more cushioning you'll have.  The lower the air bag, the less space you have in the air bag and the suspension becomes more reactive-translated it will ride rougher. 
If you are thinking about installing manual air valves, I highly recommend you keep the factory installed automatic leveling valves and make a manual valving for leveling when stopped for the night.  I did this and it works well.  Then also, if you do blow a air leveling valve (which happens VERY rarely) you could go down the road on the manual valving.  Good Luck, TomC