I have Air bags on my bus, but its Way hard on bumps. is there to much pressure in it ?
I see most buses Floating down the road.. Mune DOESNT :o
Whats wrong here..
Thanks:
Paul...
Check tire pressures first.
Check the ride height of your air bags. Manufacturer of your bus will have a spec in the maintenance manual. If ride height is good, check shocks (leaking,broken) and shock pins (broken) too.
What kind of coach do you have??. I might have info for you.
Sammy 8)
Quote from: Sammy on May 13, 2007, 02:18:40 PM
Check tire pressures first.
Check the ride height of your air bags. Manufacturer of your bus will have a spec in the maintenance manual. If ride height is good, check shocks (leaking,broken) and shock pins (broken) too.
What kind of coach do you have??. I might have info for you.
Sammy 8)
A T6H4521 Fishbowl.. It does seem to be a bit High.. But What do I know ;D
There is a misconception that air springs ride good. Air bags do not deflect. Peterbilt Air Leaf is known as the worst suspension for breaking axle housings in the trucking industry. I know as I have changed several. If an air bag could pass air when you hit a bump, it would help, but they are not designed that way. Set your ride height and your done. Attitude is important. I like the nose a couple inches higher than the rear for several reasons, one that it may help the ride a little. It also forces air under the bus that helps dry brakes in the rain and cool brakes in the mountains. My bus has a feel almost like a boat as it comes on plane. It does that around 70 MPH. It won"t do that with the nose down and does not ride as well. Crosswinds will also blow the bus around if the nose is to low. Last, wheel alignment is important to ride, a wheel that is running out sideways is going to deflect harder than one that is nice and straight. I can't say I don't love my Torsion Bars. They are incredible. Last summer one of the kids left an almost full Coke can on the baggage floor bay rib. When I got home 180 miles later it was still balanced on the same rib and had not spilled a drop.
If you don't know your exact ride height, a good rule of thumb is to have it ride at 5/8 to its height. And the higher you set it, the more air you have in the bags for more cush of a ride. I have mine set very high (1 inch from top) and have a great ride. I have an AMGeneral transit that has very similar suspension to yours. Except I have double convoluting air bags that have a large aluminum can at the top for an air reservoir. Yours I believe are rolling lobe.
Also, the biggest factor is to have the correct air pressure in the tires. If you are running the maximum that is printed on the side of the tire, that's probably your problem. For instance, my 11R-24.5 16ply tires are rated for 14,000lbs @ 120psi in the front. But since I only have 10,500lb on the axle, I run 90psi. Have your bus weighed by axle then look up your tire manufacturer by tire size and model and run that tire pressure on the table. You'll be very surprised at the difference in ride quality. Good Luck, TomC
Thanks guys, some good info. I will look it up in the Manual to see how to set the higth on the air bags.. And, look up the tire pressure . They are Smallish tires 22.5. Wish I had the 24's but changeing all that Good rubber is Expensive..
Thanks.. PAul
I'm a bit confused about a few things here. First off I have a RTS with the IFS, which means I have one air bag per front wheel.
If I increase ride height, I am adding air pressure to do so, which will make the air bag harder and make the ride harsher.
Secondly, the comment about 22.5's versus 24's seems wrong to me also. The other diameter of the tires is basically the same. What changes is inner diameter, so on a 24" tire you have less sidewall and less air volume than a 22.5" tire so it may very well ride harsher, sidewall stiffness being taken as the same between the two. ??????
Chris- yes-if you add air pressure to the front air bags, they will ride higher. With more air volume in the air bag, the deflections are less of a percentage of the total bag height, and with the extra air in it will make for a less reactive ride, meaning it will ride better. On the other hand if the bag is too low, there won't be much air in the bag, making the area in the bag smaller, hence it will react faster making for a more busy ride, or rougher ride.
The 12R-22.5 and the 11R-24.5 have the same aspect ratio (width to height). Run at proper tire pressures, both should provide similar ride characteristics. I went with the 11R-24.5 since it is a bit higher (my bus is low since it is a transit) and a few less revs per mile to make it a bit faster. Since I used to be a cross country truck driver, I know that the 12R's are harder to find than the 11R's, that are carried at most truck stops. Most importantly to ride quality is proper tire inflation to the weight you're carrying! Good Luck, TomC
I have read several posts in the past where owners reduced the air bag pressure significantly when on the road on long drives. The reason given was to give a softer ride. Anybody got a different opinion on this?
Since I had an Eagle and the ride was always good so I never had the requirement to change air bag pressure. LOL
Richard
Here's another example of where it's really hard to second-guess the factory when it comes to ride quality. To expand upon what others have said:
First: The air suspension has specific settings listed in the shop manual for the correct ride height. These measurements are taken between the top of the axle and the rubber bump stops mounted on the chassis. Over the years, the rubber bump stops tend to compress as the coach settles w/o air in the system, so using older bump stops as the guide will not provide accurate settings. Replacements are inexpensive (for a bus!), altho replacing them may tax your patience. Once the ride height is adjusted properly, you will get the best compromise of ride quality and suspension travel as determined by the factory originally.
Second: In order to set your tire pressures properly, you must weigh your coach in "ready-to-roll" trim. Run it across a set of scales where you can obtain the weight on each axle, as this number is what's used to determine the correct pressure. Divide the axle weight by the number of tires on that axle (two for the front, four for the drive, two for the tag [if equipped]) to determine the average weight each tire is carrying. Add a fudge factor for "stuff" (I use 200 lbs) to that number, then look up the inflation table for your tire on the manufacturer's website, or contact a local dealer for the info. The inflation charts will tell you what the correct PSI should be for the weight the tire's carrying. Underinflate and you might get a softer ride, but vastly increase the potential for failure due to heat build-up. Overinflate and you'll rattle your dentures.
The easiest (and cheapest) thing to do first is to adjust your tire pressures properly as outlined above, then undertake the task of setting the ride height.
BUT PLEASE -
Do NOT crawl under your coach to set the ride height without blocking up the body correctly. Air suspended coaches will crush you very, very quickly if the suspension's tampered with and the body's not blocked. If you have access to a pit, that's a great option.
Chris -
Sad to say, but the IFS RTS's do ride a bit more harshly than a Fishbowl or other air-ride coaches. Nature of the suspension design, unfortunately. On reason GMC/TMC/MCI/NovaBus went back to the beam axle on later models. But because of that, it's all the more critical that you set it correctly to give you the best ride possible.
Richard -
I think the folk who have taken the automatic leveling feature of the air suspension out of the system, and utilized four valves controlling the four corners of the coach primarily for campground leveling, are the one's that have posted about reducing the air bag pressure for traveling. Different scenario.
BTW, IIRC, didn't you mention awhile ago that your Eagle rode a whole lot better after it had the torsion bars re-indexed back to factory specs?
FWIW & HTH. . .
;)
BTW, IIRC, didn't you mention awhile ago that your Eagle rode a whole lot better after it had the torsion bars re-indexed back to factory specs?
Russ,
Yes, you are correct and also my bogie tires quit skidding every time I applied the brakes. The drive axle was carrying too much weight. So your instructions apply to torsion bar equiped vehicles also.
Richard
Paul, I have info for you from a T6H5310 manual. It's a Fishbowl, printed in 1973.
It says to measure the distance from the top of the axle housing to the rounded edge of the axle bumper. Bear in mind that the axle bumper when it was new had a dimension of being 1 & 3/4" tall - from mounting base on frame of bus to rounded edge of axle bumper.
The front should be 3 & 1/4" and the rear should be 3 & 3/8".
Hope this will help.
Sammy 8)