Replacement Air Bags

[Jon Wehrenberg]

A while back Roger and I replaced our air springs (air bags). It started out with Roger receiving a set of the wrong air bags. I opted to do mine at the same time, and since I was aware he received the wrong ones I spoke to the parts folks in Elgin, and while we were both looking at the same parts list on our respective computers he and I agreed on the part numbers and trade numbers. We received the correct air bags and both our buses could be raised or lowered through the entire range. Both would easily be raised to road height.

I recently became aware of a POG member getting a set of air bags for the front of his coach. After installing the set the coach could not be raised above ride height. Also, the coach at the air pressure settings could not reach ride height without raising the tag axle. An increase in system air pressure did not have an appreciable affect.

After a lot of research between some POG members who may post their findings on this thread it appears that this problem is not isolated to the bus in question, but may be a widespread problem. The front air springs supplied by Prevost, either direct to you the owner, or to the mechanic in the service center will not perform like the air spring it replaces.

What this means is that if you have recently had the front air springs replaced in your coach you may not be lifting the front to the full ride height. This of course will have an impact on road clearances and may affect your steering geometry. It will also limit your ability to level the coach on an uneven campsite because you likely have lost several inches of vertical travel.

The problem lies with Prevost changing part numbers. I cannot be sure of the part numbers required for IFS coaches, or even if they are affected, but on solid axle coaches the front air bags that work are old Prevost part number 630126, trade number 1R11 296. These are what has been known as the "Mae West" air springs.

If you are about to change air springs or already have your bus should be able to travel from the full down position to the full up position which is 3" or 4" above ride height, which is about 11.5" between the top and bottom mounting pads for the air bags. Anything less than that travel and your bus has had its leveling capabilities limited. If you think that is relatively unimportant think about the next time you need to raise the front to keep from scraping on a sharp upslope like a driveway.

[Joe Cannarozzi]

The 63-0126 part # is now too no longer available. It has been replaced by part# 63-0259. I am not assuming that only the # has changed they may very well be using a bag that is configured differently too.

I will be out most of the day.

The trade # for this new part# is 1R11-244 if anyone can get dimensions and compare the two it would be something I would be interested in knowing.

We will continue this experiment stay tuned

[truk4u]

Joe & Jon,

Part number 630259 must have been around for awhile, Brain put one on the front of my Liberty on 4/07. The rears on mine are 630104.

[Jon Wehrenberg]

Tom,

Will the front of your bus raise from the full down position to the full up position without lifting the tag?

Can you speculate and let us know what aux air pressure it takes to raise the front to ride height?

It sounds like you have the correct fronts. The number for the rears corresponds with the one on my drive axle only. The tag has 630126.

For those whose front air bags are part number 630260 it is possible that air bag is for a seated bus, and that is why you cannot get full up travel. Apparently that is the air bag number that will be supplied and it is not suitable for a motorhome which relies upon the level low system for leveling.

[Joe Cannarozzi]

Well if Brian was given the 0259's then SOMEONE at prevo parts got it right.

Who was it?

I got a notion to put the 0260's on the front on ours we have a 11800 front end and I would like to know if they would lift a lighter load or if the travel is just not enough.

[truk4u]

Jon,

It takes full shop air at 120 psi to move it very slowly with the tag down. I just took it off the stands/blocks and had to cycle the shop compressor to keep the pressure high or it wouldn't come off the stands.

If the bus is running, it takes high idle and all the air it can make to move it. The front end is at gross weight, 14,000 lbs. At Mobile, I had to dump the tag to get the front up.

100 lbs of air will not lift the front

[BrianE]

Tom, yer a crybaby on this one. I doubt if 100 psi will lift the front of anyone's bus. It sure won't lift the Royale. In my short experience with the Prevost level lo system, the Liberty leveling system is far superior IMHO. Have you sorted out the Aux air problem you were having? With a leaking check valve you might not be getting enough volume to the airbags. Just a thought.

[Jon Wehrenberg]

Hate to disagree with you guys, but 100 PSI will bring my front up to almost road height. I am carrying a little over 14,000 on the front. I know this for sure because those that have seen my driveway will understand I have to drop my front to get throught the overhead door, and raise the front once outside so the baffle under the generator doesn't get crushed on the crown of the driveway. So every time the bus goes into or out of the garage I have to run the front up and down throught its maximum range of travel.

My rears come to ride height with less than 100 PSI.

My old bus with about 13,200 on the front required full pressure and a lot of time to come up to the max height and 100 PSI (aux compressor cut out) would only bring it up if the tag was lifted.

I have 630126 (1R11 296) bags in the front. Now I am really curious about exactly what bags our coaches need to have. Since Tom's coach and mine are raising almost the same weight then it follows that our air bags are different because of the different pressures required. That leads me to conclude the 630259 is NOT a direct replacement for 630126.

The plot thickens. When Dr. Joe C. changes a set of fronts this coming weekend I hope he can get some measurements. Diameter when installed deflated (at full height), maximum extended height (mounting plate on bottom to mounting plate on top), pressure at ride height, pressure to fully extend.

[truk4u]

Mole Man - The suspected check valve (if there is one) has nothing to do with this pressure issue. I would suspect the bus will go to road height at 100lbs given enough time, but beyond that, forget it. However, the rear bags seem to have no problem raising even at less than max air pressure.

The 40' Marathon I had experienced the same. It would not lift the front without dropping the tag. The CC on the other hand would come right up. The Marathon was also at max gross on the front end, same as the Liberty. The CC was about 2000 lbs under gross on the front.

Jon - Keep digging, with Joe's help, we may find there is a better alternative to the front bag issue. It appears to me the 259 bags just can't lift 14,000 lbs without help. Maybe that's just the way it is! Mine is still hooked to a 100 gallon shop compressor, so I can do a little experimenting if needed.

[Jamie Bradford]

How often do air bags need to be replaced?? Is it ok for the bus to sit for a week or more with all of the air dumped? Or should some be left in the bags?


Jamie