Need some expert air bag leveling advice

[Scott & Heather]

We have been experimenting with manual air bag control on our C3. Right now we are dialed in around 70 psi for the drivers side and 80 psi for the curbside drive axle bag pressures. Here's where it's getting weird:

I am still leaning ever so slightly to the curbside. To actually get the coach to level out, I have to run about 40 psi in the drivers side drive axle bags and almost 80 psi in the curbside bags. This makes the coach rock too much because 40 psi just isn't enough. But this is what actually seems to make it not lean. Ok, ready for the extra layer of weirdness?:

If I go into the tag axle regulator controls and raise the pressure on the tag bags from 40 psi (where they were originally set) to 60 psi, I am then able to level the coach with about 70 psi in both sets of drive axle bags. It's almost like the tag pressure helps level it out. Now, I'm confused because inside the tag regulator box there are two regulators and two pressure gauges. I can't tell what they do. One is set to 0 psi and the other to 60 now. Is one the pressure you want the bags to be when inflated and the other the pressure you want when they trailing axle switch is in the "unloaded" position? The bags for the tags don't appear to be separately controlled but I could be wrong. I am really heavy curbside because of my 150 gal fresh tank, 40 gal water heater tank, fridge, washer and dryer  and kitchen cabinets all on that side. The opposite side has the bathrooms, stove, tile shower with concrete pan and my black tank. Certainly might explain the lean but I'm trying to level this thing out with at least somewhat similar pressures. If I could just add a bit of pressure to the tag on the heavy side it would help to support some of the weight without raising the level of the tag on the light side. But is this even possible? Anyone know how the tags are plumbed?


Sent from my iPhone using Tapatalk

[Jon]

What is wrong with using leveling valves which are always working to keep the coach level?

[gumpy]

Of course you realize that as you use your fresh water, it ends up in the black tank on the opposite side of the bus?

Aw, the beauty of dynamic automatic leveling devices.

On the MC9, the tag pressure is set at 35 psi. The amount of pressure in the tag bags regulates the percentage of weight the tag axle carries. The higher the pressure, the more weight on the tag, and hence, the less weight on the drives and steer. I encourage you to not deviate from the manufacturers specifications on tag pressure for your model bus.

[Oonrahnjay]

      Plan to fit in a few minutes on the scales next time you're at a well-equipped truck stop for fuel.  Ask them if they can weigh axle to axle and side to side.  It will tell you a lot.  And I agree with Gumpy, the tag pressure has effects all along the bus (the higher the tag, the higher the load is on the front end, for instance) -- don't mess with it too much unless you're absolutely sure what you're doing is necessary and safe.
      (If you have already weighed your bus, please post the individual corner weights here to help us understand what's happening with your "coach".)

[luvrbus]

I am going to for go the air bag leveling system and go with the HWH hydraulic 4 point system and be done with it,there not enough leveling range with air bags to really do any good   

[blue_goose]

First question, do you have lifting springs on the tag to lift them when the air is off?  Why did you take the leaving valves off the coach.  My C-3 has a MCI installed leaving system and still has the leaving valves.  If you need I have the info from MCI as to how it works.
Jack

[B_K]

I know I know I'm an old school reject but......
IF IT WERE ME.... I'd go back to the factory leveling valves but go one step farther by putting one on each side of the front instead of just the one in the center.
Once set for correct height they should keep the bus level as it travels up and down the highway as well as maintaining a good ride.

If you wanted you could put solenoid valves on there and leave your added system for use when parked, but honestly I'd think the factory system would do OK there too.

Just my opinion which when combined with $3 will by you a cup of coffee at the nearest Flying J or Pilot!
  BK 

[RJ]

Scott -

Question: Did you remove the OEM stock leveling valves?

Regardless, you need to get out DaBook and open it to the suspension section. In there you will find the dimensions for the stock clearance between the rubber bump stops on the chassis and the axle.

Armed with that information, get your bus over a pit so you can adjust the ride height to factory specs - FORGET your air pressure settings until you've set your ride height correctly. Once you've got everything set to specs, THEN make note of the individual air pressure readings.

Without setting the ride height to specs, it's simply the blind leading the blind...

FWIW & HTH...

[B_K]

RJ from my understanding yes he removed the stock levelers and just went with his own designed individual gauge per bag w/valve system.

Not saying there is anything wrong with going the route he did, just that I believe the engineers that designed the bus did a good job in the first place and the only thing I don't like about it is the single leveling valve on the steer axle of the MCI (of that vintage)

Now had it been a Setra w/independent front suspension he would not have wanted to change it in the first place!
  BK 

[Scott & Heather]

Correct I have bypassed the leveling valves. The ride height was set and the leveling valves were brand new but the coach rocked side to side so bad it was making us all sick and was downright dangerous. My 9 never ever did this. Once I went manual and added air, she drives rock solid. My only issue is the slight lean which I'm trying to sort out. I do need to get over a pit and measure bump stop clearances. Jack if you do have a diagram on the air suspension system I would love to gander at it to see if the tag pressure is controlled separately for each side or in tandem


Sent from my iPhone using Tapatalk

[Jon]

What leveling valves are you using? There are instant acting which add or dump air almost as fast as the arm moves which would give you that ride characteristic, or the delayed action that are not going to react for a few seconds which provide less rocking. Also, has the coach got sway bars? They make a huge difference in side to side swaying, and most of all is bad shocks are going to allow the mushy feel.

Take them off and compress and pull them. They should move b ut very slowly and with resistance. If they move freely they are worn out.

[luvrbus]

You need to buy the leveling valves from MCI so much of the time PO install leveling valves from trucks or trailers MCI use their own design and cost 2x the amount of leveling valves you find on the internet, don't use a universal leveling valve on your MCI

[Scott & Heather]

The leveling valves move freely when disconnected. And instantaneously. They are brand spanking shiny new. I didn't buy them but PO did. I doubt they are MCI valves but I could be wrong


Sent from my iPhone using Tapatalk

[buswarrior]

Proper suspension ride height is critical for drive shaft angles and front steering suspension geometry.

Set ride height by a measuring tape, and beware the effect of crushed axle bump stops if you use that measurement...

You MUST have proper BUS leveling valves.

MCI corner comfortably, from the driver's seat of the pants, at higher speeds, and flatter, bumpy road, side wind, than the rest of that vintage.

Return it to stock, with the correct parts, you will be happy!

happy coaching!
buswarrior

[blue_goose]

Send me your email address for me to send the drawing of air system.  The tags both run the same pressure.  Some of my friends have raised the pressure in the tags and say it gives a better ride.  My C-3 with the factory setup dose fine, no problem.  My air leveling system can be set for auto or manual.  When on manual it just bypasses the leveling valves.
Jack