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?
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What is wrong with using leveling valves which are always working to keep the coach level?
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.
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".)
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
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
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!
;D BK ;D
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...
;)
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!
;D BK ;D
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
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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.
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
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
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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
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
Scott,
I don't know one specific thing about your setup, so I'll put my fireproof unders on for the flaming.
On my coach, which I know is way different than yours, it takes around 60 psi to raise the coach of off dead flat. Do you know what that value is for your rig?
The point is this, the higher the air pressure in any air bag, the stiffer the spring rate. I have no doubt that if you are running 40 lbs in one side that it is mushy on that side and likely to sway.
The second thing is that you commented on lack of understanding of the tag pressure regulators. I would spend some time tracing that system, because if the assumption you made that the right and left tag were NOT independent is incorrect, then different tag pressures on each side could explain why you are seeing the side to side differences. Again, I don't know beans about your setup. But my tags are independent, and even though they appear to be connected to a common frame rail tank, that tank has a divider welded in the middle.
I could be all wrong, but this is easy to try. What happens if you set both tag regulators to the same pressure? Does that make a difference in the side to side pressures required to level the coach?
My apologies for offering advice on a system I have never seen, BUT the basic laws of physics still apply. The weight that an airbag supports is a straightforward calculation. Divide the diameter of the airbag by 2, square that number, multiply by pi (3.14),multiply by the psi. For example an airbag of 6 inches in diameter running 50 psi will support 1413 pound 6/2 = 3, 3 X 3 X 3.14 = 28.26, 28.26 X 50 = 1413. The point is this, if you are truly running 80 psi on one side and 40 on the other, then the coach would have to be twice as heavy on the 80 psi side. We know that's not reality, so something else is going on.
If XX PSI brings the coach to the road or driving height it typically means the air bags are extended to about where they are going to have 3 or 4 inches of travel up and down. If you increase the pressure the bus will sit higher and the amount of travel up and down is going to change to where there is more travel down than up. Conversely if you do not bring the coach to the driving height by introducing less pressure than required the bags will provide a mushier ride and will bottom more easily and there will be more up travel available.
Ride height valves are the only way to assure the correct height and provide the ride and handling the designers wanted.
There is no way a driver can sense if the bus is too high or too low from the driver's seat, and either position, high or low has an impact on handling and driveability.
The Warrior is right as is Jon. IMO, Those height valves are important. The bags are important. I have a spare set of both, just in case.
And from personal experience when I was a child..(behind a friends bus that wrecked as a result) if you play too much with the bags, it strains the bolts and the rubber. You do NOT want one of them to fail going down the road.
Thanks for the conversions Richard!
I'm not a Prevost or MCI guy and know nothing about them but...... the one question that should be answered is...... Do you think you're smarter than the guys that designed this system in the first place? If the answer is no, then fix it as it was designed. If you're trying to "fix" another problem, then design and build another system and leave what's there, as it was engineered.
I could probably hang this comment on the majority of threads on ALL of these boards. When I got started working on the Scenic's I quickly discovered that I spent far more time fixing and undoing other peoples "fixes" than actually repairing worn out parts and system.
I still have the stock, automatic leveling valves. I also have my own designed manual leveling system using the 3 points. I like not having to worry about leveling while driving, but able to level the bus in less than a minute. Also, have had a leveling valve go out (actually the connecting rod came loose) while driving. Simply threw the switch to manual, leveled it out and continued driving. Best of both worlds. Good Luck, TomC
I am totally game for going back to the leveling valves. They are still there. But the brackets the rod connects to are bent and look custom. One of them is actually rubbing the shock absorber. That has to be rectified before I re connect the leveling valves because they just aren't working right.
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Scott
since you have to rebuild or replace that bracket anyway. Why not make the bracket so that you can move it from a remote location. Bob from Indiana did it. You still have leveling when parked just put it in a home position for traveling and ride height is automatically adjusted. Sean also did it with linear actuators very slick.
Rick
Rick, we did that using push/pull cables. Similar to what Bob did, as I remember. I am not sure how Scott is adjusting the air in the bags, but if it is a remote system, like on the dash, it would seem that he would be able to integrate that with the automatic ride height controls as others have done.
Air bag leveling is better than nothing but is limited to about a 6 inch differential from back wheels to front, that's a only about 1 inch per five foot of incline for a 40 foot bus. I am happy that I have it, but I would be real happy if the tooth fairy installed a real leveling system for me.
Scott,
If I have read this thread correctly, the initial reason you abandoned the height control valves was the side to side sway and mushy handling. Then, if you level the coach with your manual system by high inflation on the curb side and low inflation on the drivers side, it behaves in a similar fashion.
Then if you run higher pressures in the tags, you don't have to bias the side to side pressure with your manual system to get the coach to ride level.
I really think you need to dig into the pneumatic system for the tags. It could be you have unequal pressures from side to side on the tags, and regardless if you level the coach manually or allow HCV's to do it you have the mushy handling.
Agree with Richard. We have independent bag adjustment and don't have those problems at all. But we also don't have tag axle. So would seem that it may be your tag Axle has a problem. If you want both systems to work you could use the solenoids like Tom C did also.
Dave
Thanks Richard and Dave. This is exactly what I'm trying to diagnose. The issue isn't with ride height or even the leveling valves. I am essentially doing the same thing as the leveling valves but manually. And for those that think the leveling valves adjust for when you go around a turn etc, that's somewhat bunk. The 1/4" lines cannot allow enough air into the bags to adjust that quickly. Sorry, my 9 with factory leveling valves never adjusted very much around corners or turns. It just leaned. Plus, if your valves indeed did have the ability to adjust that quickly, you'd have an unlevel bus once the turn was completed and you were driving straight down the road. Manual control of the bags is actually pretty awesome. I have no desire to go back to leveling valves. I just need to sort out tag pressures cause that appears to be part of the issue. And frankly I get weary of hearing people say "if the MCI engineers designed it that way, then you'd better leave it that way unless you think you're smarter than the engineers" because frankly, yeah I have actually done away with a ton of stuff on both my buses that the "engineers" designed because it didn't fit my needs. My air door has the air shock removed because I wanted a normal door action with mere hinges. I moved my temp gauge because the engineers decided it was a good idea to put that down so low you can't hardly see it on the dash. I have electronic wipers because the engineers thought in 1992 that air wipers would be superior to electronic wipers that all the school buses and millions of cars and semi trucks had. I moved my air brake knob and transmission touchpad to the left side arm rest area because the engineers designed it to be on a pillar on the right side even thought I kept smacking that short differ with my calf getting in and out of the seat. I could go on and on. I like my manual leveling, and I have set the ride height per specs, but I think I have a tag that is helping the drivers side more than the passenger side and causing the slight lean so I'll need to sort that out.
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What it your front set at? Different bus but my rr 54 lr 50 rf 42 lf 46 for factory ride height. I'll drop it two inches for interstate highways. Has worked for 17 years. rdw
Some adjust for the road crown of about 5 degrees that they use for road run off but we don't. 80 in the front and 75 in the back and good to go.
on the M C I rear 42 lbs front 70 lbs and I too adjust for the crown in the road or a strong side winds when needed
and love the fact that I can control it right at the driver seat when driving
dave
Dave your C3 had 42 lbs in rear both sides and it didn't rock side to side? Wow.
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Dave5c, what are you driving again? MCI?
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gg04, I don't have the front manual set yet so I have no idea
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no problems in over 10 years . before I removed my org. valves I measured the height at the 1st bumper strip and to get the coach at the same level this is the air pressure I need when driving
but as luvrbus would say jello bags due bounce ( and now he has some on his coach )
dave
Scott laughing at your question what do I drive. Yes MCI MC 5C Saudi coach. ;D
We also have only had to use our riser block a few times. If you measure the distance of travel from full down to full up on a standard coach it is almost 4 inches at the axles. But if you consider the overhanges front to back which is another 6 to 8 feet depending on your coach and you drop the tail or rear axle bags as low as they will go mine almost puts the bottom of the bumper on the ground and the front bags all the way up 4 inches at the front axle plus the overhangs. You measure it from the ground will be between 7 to 12 inches. So that is quite a bit of adjustment and side to side is enough to level it out.
Dave5Cs
hmm, low riding
Scott,
Did you ever figure out why the drastic difference in side to side air bag pressure required to level your coach?
Scott, have you ever checked the ride height with all the bags deflated? That would be my starting point.
If I remember correctly the whole reason for the tag axle was for stability reasons. If you increase the air pressure on the tag axle it transfers MORE weight onto the steer axle (drive axle acts like a fulcrum). On my coach there is a traction switch that decreases the tag axle air pressure (by about 30% if memory serves me correctly) for times that you are stuck. It in effect transfers more weight onto the drive axle for increased traction. Regardless of the tag axle air pressure there is no effect on side to side balance.
It may be a little bit of work but if you have easy access to your pressure gauges try swapping them side to side and see if you pressures read differently.
There are only two things that make the vehicle lean - pneumatic difference or mechanical difference (incorrectly matched bags, suspension mounting point differences, grossly overloaded to one side, twist in the body :o, etc.)
I won't be able to hold my hand steady enough.
I have not yet sorted this out. With all bags deflated completely the coach sits level if on a level surface. To keep the coach level during driving, this is what I have to have the settings at:
Drivers bags: 75psi
Curbside bags: 70psi
Tag bags: 58 psi
If I drop the tag bags to 40psi, the curbside drops out of level. It's weird. I am loaded heavy on that side with washer, dryer, kitchen cabinets, 40 gallon water heater, and 150 gallon fresh tank.
Other side has full tile shower with mortar shower pan, stove, both bathrooms, black tank, and that's about it. So the only thing I can think of is that I'm heavy curbside. I need to scale just that side of the coach to confirm this.
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This might be irrelevant, but is it possible (in addition to being heavy on one side) that the 8" roof raise and tire size could contribute to this problem?
Just a thought.
You will not have control until you can control the front bags. Your fighting the factory controls, you adjust they resist. rdw
Roof raise won't cause it to lean. Tire size is the same all around and it did this when I had 22.5's on the coach before I switched over to 24.5's. I raised the roof 9" on my MCI 9 bus and never had this issue. I really think I'm over weight on that side
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Scott which oil :o do you use?!...
Dave
Quote from: Dave5Cs on January 07, 2017, 08:04:23 PM
Scott which oil :o do you use?!...
Dave
Yeah, 15W-40 will make it lean like that.
Quote from: Oonrahnjay on January 07, 2017, 08:17:59 PM
Yeah, 15W-40 will make it lean like that.
as will Delvac :)
He must be "leaning" towards synthetic .....
I actually run she'll 50wt :) way too Heavy apparently
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Quote from: Scott & Heather on January 08, 2017, 08:02:54 PM
I actually run she'll 50wt :) way too Heavy apparently
Oh, yeah, way too heavy on one side, besides that, it'll give you athlete's foot and that itches! You GOT to have just the right oil!
Scott have you got a CO-OP or any other type of "grain elevator" or Ag operation near you?
If so most of them have a scale right in front of the office that is level and during slow periods will often let you use their scale for a small fee where you can drive just one side of the coach on the scale one axle at a time and then turn around and do the same from the other direction for the other side.
That will get you the actual weights from each axle side to side and all.
OR you could get a hold of Bill Gerrie and find out when the next time he's headed south to the US and see if he'll bring his scales w/him! ;)
;D BK ;D
You know, I'm actually trying to get pulled over by a commercial enforcement office so he can weigh me.... lol. Kidding. That would be suicide. I'm going to see what I can do about getting side to side scaled when I get back to Texas in a couple of weeks. I've got to sort this out so that I know what I'm dealing with.
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Well if ya had more time between Chattanooga and your recording sessions in IL I'd say swing by here and we'd get it weighed and figured out.
But best I remember that is the 16th/17th and I leave for NY on the 17th.
But there are PLENTY of Ag places in TX that should have scales that will help you out for a small fee.
;D BK ;D
Lol. You know my schedule better than I do :) I'll get this done in Texas for sure. In other news I'm thrilled that I finally had my hubs converted to synthetic grease! My life is so much happier
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