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Author Topic: Dumb suspension question  (Read 1246 times)
Tikvah
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« on: December 18, 2013, 06:37:09 PM »

I have an MCI 102-A3, like all MCIs it has the airbag suspension.  Everyday when I step in and out of my coach it moves a little.   I can actually feel it rock when we walk across the floor.  Not much, but some.

So, the dumb question is this:  If there is no air in the bags (bus air has been on zero for a month) why does the bus move?  What is is sitting on? 

I just assumed that without air the thousands of pounds of bus would settle down to some kind of heavy metal support.  It can't possibly be 'sitting on air"... there isn't any.

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I couldn't repair my brakes, so I made my horn louder.
1989 MCI-102 A3
DD 6V92 Turbo, Alison
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Started in Cheboygan, Michigan (near the Mackinaw Bridge).  Now home is anywhere we park
Oregonconversion
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« Reply #1 on: December 18, 2013, 06:38:22 PM »

Good point. Never thought of it that way. My MC8 does too.
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John316
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« Reply #2 on: December 18, 2013, 06:41:43 PM »

It eventually settles down onto the frame stops. At that point it is basically sitting on your tires. You will still have movement because the tires are filled with air.
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MCI 1995 DL3. DD S60 with a Allison B500.
Tikvah
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« Reply #3 on: December 18, 2013, 06:44:26 PM »

hmmm, nice try John, but I can actually see the movement between the body and tires when Amy is moving around inside. 
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I couldn't repair my brakes, so I made my horn louder.
1989 MCI-102 A3
DD 6V92 Turbo, Alison
Tons of stuff to learn!
Started in Cheboygan, Michigan (near the Mackinaw Bridge).  Now home is anywhere we park
Seangie
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« Reply #4 on: December 18, 2013, 07:30:37 PM »

Dave,

There is more to the suspension then just airbags.  Not 100% sure but I'd be very surprised if you didn't have shocks on your bus.  There also needs to be some kind of suspension between the axle and the frame as well as the tire and the axle of the bus.  Air bags give you a cushion but they are not completely preventing the axle and tires from slamming into the body of the bus.  

If you have your maintenece book you should read through it.  Lots of good stuff (good reading when you can't sleep).

-Sean


www.herdofturtles.org
1984 Eagle Model 10S
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« Reply #5 on: December 18, 2013, 07:34:27 PM »

Dave, I should have said that is the way ours works. If I drain the rear air bags, for example, it sits on the frame stops.

Yours might be resting on the gas shocks?
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MCI 1995 DL3. DD S60 with a Allison B500.
Dave5Cs
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« Reply #6 on: December 18, 2013, 08:07:18 PM »

Dave shocks and rubber bump stops sit on flat metal pads between the airbag platforms at the axles. The rubber stops are about 2 inches high. Your Radius Rods also help support the bus. Put it all together with the air in the tires and you will have movement.
Dave
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chessie4905
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« Reply #7 on: December 19, 2013, 02:30:49 AM »

   Even when at zero, there can be air still in the airbags. That gage only tells of the pressure in the main air tank.
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TomC
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« Reply #8 on: December 19, 2013, 06:08:23 AM »

As stated previously, even when the air pressure is zero in the tanks, the air bags can still be inflated. You'll be able to tell if the air bags deflate down to the rubber bumpers inside the air bags-when you walk around the bus it will bounce differently-much faster. I have manual controls over my air bags. If I'm at a parking spot that is level, I'll dump all air out of the air bags to become a low rider-then I don't need the exterior step to get into the bus. Otherwise, I use the manual dump switches to level the bus out in just a few seconds. The only way to stop feeling someone walking around the bus is to install hydraulic landing gear that support the bus by leveling on the ground-very hard-very expensive without a chassis. Good Luck, TomC
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Tom & Donna Christman. '77 AMGeneral 10240B; 8V-71TATAIC V730.
luvrbus
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« Reply #9 on: December 19, 2013, 06:14:32 AM »

Or buy a Eagle  Roll Eyes
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Tikvah
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« Reply #10 on: December 19, 2013, 07:08:57 AM »

So, to make this easy, just like a flat tire, there is still some air in it.  Even though the airbag is deflated, the flat bag still has some ambient air that moves with the movement of the coach.

Am I thinking right?

P.S.  I don't mind that it moves, and I don't plan to spend big bucks to change it.  I was just curious. 
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I couldn't repair my brakes, so I made my horn louder.
1989 MCI-102 A3
DD 6V92 Turbo, Alison
Tons of stuff to learn!
Started in Cheboygan, Michigan (near the Mackinaw Bridge).  Now home is anywhere we park
B_K
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« Reply #11 on: December 19, 2013, 07:17:25 AM »

So, to make this easy, just like a flat tire, there is still some air in it.  Even though the airbag is deflated, the flat bag still has some ambient air that moves with the movement of the coach.

Am I thinking right?

P.S.  I don't mind that it moves, and I don't plan to spend big bucks to change it.  I was just curious. 

Yup you got it.

As you put it a flat tires still has air in it! (of course it does, it's only flat on the bottom ain't it?)
Grin  BK  Grin
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TomC
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« Reply #12 on: December 19, 2013, 07:33:43 AM »

No, you don't get it. Just because the air pressure gauge says zero, doesn't mean the air bags are deflated. If you have a sound air suspension system, you can have zero air pressure in the air tanks, but have the air bags fully inflated for weeks. That's why you get bouncing when the air pressure is at zero, but still have full air pressure in the air bags. The air suspension has their own leveling valves. Once the air bags are up to level, the leveling valves turn off the air supply, and is in the neutral position. If you get out of the bus you'll hear the air bags expelling air to keep the bus at the pre set height. Good Luck, TomC
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Tom & Donna Christman. '77 AMGeneral 10240B; 8V-71TATAIC V730.
chessie4905
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« Reply #13 on: December 19, 2013, 07:44:37 AM »

With all the rust, Eagles will bounce too  Grin
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Scott Bennett
Scott & Heather MCI-9
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« Reply #14 on: December 19, 2013, 07:55:52 PM »

We stop jacks under our jack points under our mc9 and it is as solid as a house. No bounce at all


Sent from my iPhone using Tapatalk. Clumsy fingers may contribute to mistakes.
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Scott & Heather
1984 MCI9 6V92-turbo with 9 inch roof raise & conversion in progress.
http://www.scottmichaelbennett.com/p/our-bus.html
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